From Physical Aggression to Verbal Behavior: Language Evolution and Self-Domestication Feedback Loop

Frontiers in Psychology | www.frontiersin.org 1 December 2019 | Volume 10 | Article 2807 HYPOTHESIS AND THEORY published: 18 December 2019 doi: 10.3389/fpsyg.2019.02807 Edited by: Danielle Sulikowski, Charles Sturt University, Australia Reviewed by: Slawomir Wacewicz, Nicolaus Copernicus University in Torun´, Poland Constantina Theofanopoulou, The Rockefeller University, UnitedStates *Correspondence: Antonio Benítez-Burraco [email protected] Specialty section: This article was submitted to Evolutionary Psychology, a section of the journal Frontiers in Psychology Received: 12 May 2019 Accepted: 28 November 2019 Published: 18 December 2019 Citation: Progovac L and Benítez-Burraco A (2019) From Physical Aggression to Verbal Behavior: Language Evolution and Self-Domestication Feedback Loop. Front. Psychol. 10:2807. doi: 10.3389/fpsyg.2019.02807 From Physical Aggression to Verbal Behavior: Language Evolution and Self-Domestication Feedback Loop LjiljanaProgovac1 and AntonioBenítez-Burraco2* 1 Linguistics Program, Department of English, Wayne State University, Detroit, MI, United States, 2 Department of Spanish Language, Linguistics and Literary Theory (Linguistics), Faculty of Philology, University of Seville, Seville, Spain We propose that human self-domestication favored the emergence of a less aggressive phenotype in our species, more precisely phenotype prone to replace (reactive) physical aggression with verbal aggression. In turn, the (gradual) transition to verbal aggression and to more sophisticated forms of verbal behavior favored self-domestication, with the two processes engaged in a mutually reinforcing feedback loop, considering that verbal behavior entails not only less violence and better survival but also more opportunities to interact longer and socialize with more conspecifics, ultimately enabling the emergence of more complex forms of language. Whereas in the case of self-domestication, sexual selection has been proposed to work against physical aggression traits, in the case of verbal insult, the selection has been proposed to work in favor of verbal aggression. The tension between these two seemingly opposing forces gets resolved/alleviated by a tendency to replace physical aggression with verbal aggression and with verbal behavior more generally. This also helps solve the paradox of the Self-Domestication Hypothesis regarding aggression, more precisely why aggression in humans has been reduced only when it comes to reactive aggression, but not when it comes to proactive aggression, the latter exhibiting an increase in the advent of modern language. Wepostulate that this feedback loop was particularly important during the time period arguably between 200 and 50 kya, when humans were not fully modern, neither in terms of their skull/brain morphology and their behavior/culture nor in terms of their self-domestication. The novelty of our approach lies in (1) giving an active role to early forms of language in interacting with self-domestication processes; (2) providing specific linguistic details and functions of this early stage of grammar (including insult and humor); (3) supplying neurobiological, ontogenetic, and clinical evidence of a link between (reactive) aggression and (reactive) verbal behavior; (4) identifying proxies of the earlier stages in evolution among cognitive disorders; and (5) identifying specific points of contact and mutual reinforcement between these two processes (self-domestication and early language evolution), including reduction in physical aggression and stress/tension, as well as sexual selection. Keywords: language evolution, self-domestication, reactive/proactive aggression, verbal aggression, neurolinguistics, language disorders, child development, sexual selection Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 2 December 2019 | Volume 10 | Article 2807 INTRODUCTION Here we propose that human self-domestication (the presence in humans of morphological, physiological, behavioral, and cognitive features commonly found in domestic animals) co-evolved with a gradual transition from in-group (reactive) physical aggression to inter-group (complex) verbal behavior via (reactive) verbal aggression, in a mutually reinforcing fashion. We explore here in detail the possibility that the emergence of the simplest forms of language/grammar accelerated processes of self-domestication and brain evolution already underway, which in turn fueled the transition to more complex languages. Early verbal creations would have afforded an adaptive (non-violent) way to compete for status and sex (e.g., Progovac and Locke, 2009), accelerating/reinforcing self-domestication, while enhanced self-domestication provided a richer niche for extended communication and language learning enabling the transition to more complex forms of language. Language – communication relying on syntax and grammar – is usually construed as a human-specific cognitive faculty that resulted from biological changes (e.g., Bolhuis etal., 2014; Chomsky, 2017). As a consequence, its history is generally reconstructed by looking for proxies of language in extinct hominin species and for (deep) homologs of language in extant species. By contrast, emergence and divergence of modern languages across the globe are presumed influenced by the physical environment, and social and cultural practices, with such influences largely confined to non-grammatical, lexical components. As a consequence, the history of languages is traced with a minimal reference to changes in brain, behavior, and cognition. There is ample evidence that socio-cultural factors do indeed influence the divergence of modern languages, and this goes well beyond the attested effect of social factors on linguistic diversity within a language (as studied by Sociolinguistics) or on the lexicons of world languages (as studied by Anthropological Linguistics). For instance, the number of speakers seemingly contributes to explain the morphological complexity of languages (Lupyan and Dale, 2010). Likewise, computational modeling, experimental work with human learners, and language emergence in certain cultural contexts (like the homesigns developed by isolated deaf communities) have shown that core properties of language, such as duality of pattern or compositionality, can emerge by iterated learning and cultural transmission (Sandler etal., 2005; Tamariz and Kirby, 2016) and that the same cognitive and biological biases can result in different language features in different cultural environments (Thompson et al., 2016). Increasingly, however, evidence suggests that language structure also impacts on basic cognitive abilities, such as effects of word order on working memory (Amici et al., 2019). As a consequence, language features, language learning, and cognitive architecture comprise a reinforcing feedback loop (Deacon, 2003; Clarke and Heyes, 2017), wherein genetic changes occurred to accommodate language-specific cognition (Jablonka etal., 2012). The greater cognitive cost of language processing and learning incurred by certain recently evolved languages might have necessitated cognitive adaptation because of the enhanced demands on working memory and executive control (Benítez-Burraco and Kempe, 2018). In brief, we should expect not only that our cognitive architecture accounts for many aspects of the languages we speak, but also that certain language features, resulting from cultural and environmental factors, affect, more or less permanently, our cognitive architecture. These two aspects cannot be detached one from the other. We have a good understanding of the morphological changes that apparently afforded language readiness, including brain rewiring associated with the globularization of the human skull/brain, which is a distinctive feature of our species when compared to the elongated shape found in Neanderthals and Denisovans (for details, see Boeckx and Benítez-Burraco, 2014a). Likewise, we also appreciate the changes in human behavior and culture that affect language structure and divergence1. However, welack good hypotheses about the feedback loop between these two processes. One possibility is that the biological changes that brought about our species also favored the creation of the niche that enabled the emergence of aspects of language complexity via cultural evolution, which in turn affected our biology. Another possibility, not mutually exclusive, is that certain cultural practices affected our biology and paved the way toward specific cognitive changes that enabled the emergence of language complexity. Human self-domestication might have contributed to both processes, the evolution of our language-ready brain, mostly via biological mechanisms, and 1 These two processes are expected to have incurred in some sort of gradualism (which is not incompatible with occasional punctual sudden changes). In truth, gradual changes have been reported for the globularity of the human skull. According to Neubauer et al.’s (2018) study of endocranial casts, hominin fossils from first anatomically modern humans did not exhibit this type of globularity, in clear contrast to human skulls from more recent periods, which they found to be within the range of modern humans. They also identified an intermediate stage in the evolution of globularity, with the fossils dating somewhere between 130 and 100 kya. Overall, in the first step of this process, approximately 200–130 kya, the frontal area became taller, and the parietal areas and the cerebellum bulged and became larger, while the occipital area became more rounded. The second step, roughly 130–100 kya, involved size changes primarily in the cerebellar and occipital areas. Both steps contributed to the globular shape of the human skull. Neubauer et al. (2018) further suggested that the initial changes in the shape of the skull were caused by brain reorganization, rather than changes in the shape of the face, which are typically found in domesticated animals. Moreover, these morphological changes in the evolution of humans were not likely to have been a result of genetic drift, but rather of selection, given that there is evidence for positive selection of several genes expressed in brain development, including the genes responsible for axon and dendrite growth. Something similar occurs with our behavior, including our cultural practices. Based mostly on archeological findings, Mellars (2002) and others initially proposed that there was a major cultural and cognitive transition/revolution around 43–35 kya. However, later discoveries led to a revision of this view, pointing to a more protracted, gradual accretion of culture (see e.g., McBrearty and Brooks, 2000; McBrearty, 2007; Mellars, 2007, p. 3). Neubauer et al. (2018) further note that the globularization timeline parallels the emergence of behavioral modernity, culminating around 50–40 kya, suggesting that some of those genes expressed in brain development were selected and fixed. In summary, comparable to the morphology of the skull/brain, behavioral modernity also represents a culmination of gradual accretion over time, rather than a single rapid evolutionary event. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 3 December 2019 | Volume 10 | Article 2807 the creation of modern languages mostly via cultural mechanisms. Prior proposals linking language evolution with self-domestication in humans (e.g., Thomas and Kirby, 2018) seem to assume a unidirectional causal relationship, whereby self-domestication contributed to the emergence of language readiness and of complex languages. Such proposals have not advanced explicit hypotheses regarding how some specific language expressions/structures would have contributed to self-domestication processes and thus to the biological aspects of human evolution. Here we explore such a possibility in detail. THE LANGUAGE EVOLUTION/ SELF-DOMESTICATION FEEDBACK LOOP: A HYPOTHESIS Compared to our primate relatives (perhaps with the exception of bonobos), and to species of extinct hominins, present-day humans exhibit reduced aggression (Herrmann etal., 2011). Morphological changes indicative of reduced aggression appear in the fossil record alongside an increase in cultural artifacts, from around 80,000years ago (Hare etal., 2012). The human self-domestication hypothesis (Hare, 2017) proposes that these changes evolved when natural selection favored increased in-group prosociality over aggression in human evolution. Accordingly, as a by-product of this selection, present-day humans are thought to exhibit most of the physical, physiological, and behavioral traits commonly found in domesticated strains of animals compared to their wild conspecifics, including reduced cranial robusticity and brain size, neotenic features (mostly affecting the face), reduced sexual dimorphism, reduced aggression, increased playing behavior, enhanced socialization, and reduced responsiveness to stress as measured by cortisol levels (Shea, 1989; Leach, 2003; Somel etal., 2009; Zollikofer and Ponce de León, 2010; Herrmann etal., 2011; Plavcan, 2012; Márquez et al., 2014; Fukase et al., 2015; Stringer, 2016). This is seemingly due to the fact that selection against aggression inhibits the proliferation of the neural crest cells (NCCs), ultimately affecting the development of many body components (Wilkins etal., 2014, but see Sánchez-Villagra and van Schaik, 2019 for some cautionary notes). Less aggressive behavior resulting from our self-domestication might have specifically enhanced learning and teaching opportunities and our capacity for knowledge exchange and group collaboration, ultimately supporting an increase in language complexity via a cultural process (Benítez-Burraco and Kempe, 2018 and Thomas and Kirby, 2018). However, this broad picture has to beproperly qualified. In spite of the trend toward increased in-group tolerance and prosociality, demographic pressures during the last part of our history seemingly increased inter-group aggression (Choi and Bowles, 2007). As a consequence, although reactive physical aggression (that which arises from fear or anger) has declined over time, inter-group proactive aggression (which strategically aims to achieve specific outcomes) has increased (Wrangham, 2018). Our proposal, which gives the emergence of language an active role, helps explain this otherwise surprising discrepancy between in-group and inter-group violence, which cannot be explained solely by self-domestication2. Interestingly, while proactive aggression seems to betied to complex language/cognition, derogatory language, like swearing, is typically reactive, reinforcing our idea that it serves well to replace reactive physical aggression, specifically, and that it represents an early stage in the evolution of language complexity under the selfdomestication hypothesis3. While some reactive physical aggression persists, it has been largely replaced by reactive verbal aggression. Verbal rituals have persisted throughout recorded history (Locke and Bogin, 2006; Locke, 2009). Such duels with words, as opposed to fists, providean adaptive way to discharge aggressive dispositions (Marsh, 1978) and to compete without risking physical harm (Locke, 2008). Although verbal duels may bea cathartic purging of aggressive impulses, their beauty, creativity, artistic value, and cultural specificity have also been observed by many (Darmesteter, 1934; Samarin, 1969; and Pagliai, 2009). While linguists tend to focus on the language function of conveying information (and have tended to “sanitize” the language they study, excluding swearing, Bergen, 2016, p. 3), there are other, expressive, esthetic, and profane aspects of language, which are just as relevant in the context of language evolution (Haiman, 2013). Both verbal aggression and creativity are directly relevant to our proposal, showing the multiple adaptive advantages of using linguistic aggression over physical fighting (see section “Emergence of Proto-Syntax and Verbal Aggression (Insult)” for further discussion). Direct verbal confrontation often makes use of simple forms of language, as illustrated with, e.g., crude compounds consisting of just one verb and one noun [e.g., English kill-joy, pick-pocket, scatter-brain, turn-coat, cry-baby; Serbian cepi-dlaka “split-hair,” vrti-guz “spin-butt” (fidget), ispičutura “drink-flask” (drunkard), jebi-vetar “screw-wind” 2 Some differences exist between primate and human inter-group aggression, considering that humans usually form peaceful relationships and alliances among groups (see Wrangham and Glowacki, 2012 for discussion). Socially coordinated violence (proactive aggression) potentially became possible only with the onset of symbolic thought and complex cognition because the same capacities for communication and sociality allow warfare and conflict resolution and avoidance (Kissel and Kim, 2019). In fact, features of self-domestication reached a peak at the end of Upper Paleolithic (Cieri et al., 2014), right before collaborative inter-group conflicts became widespread during the Neolithic, as shown by genetic evidence (Zeng et al., 2018). 3 While it may betrue, as pointed out by a reviewer, that derogatory language can be used playfully in an endearing way, this is of course also true of physical aggression, such as hitting. This does not undermine the view that the primary function of both of these phenomena is aggression. As the reviewer also points out, complex language can certainly beused for derogatory purposes, even when seemingly polished and polite. This does not pose a problem for our approach, which associates such complex, pragmatically refined capabilities with the later developments in human evolution, which brought about more complex forms of language, with more sophisticated pragmatic skills, and, arguably, also more sophisticated tools for planning and coordinating proactive aggression. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 4 December 2019 | Volume 10 | Article 2807 (charlatan)]. As such, very simple grammars can suffice for verbal aggression and insult. Significantly, these compounds, which afford a particularly creative strategy for coining names with derogatory reference, have been analyzed as approximations of the earliest stages of grammar, showing both crude syntax and primitive vocabulary (e.g., Progovac and Locke, 2009; Progovac, 2015, 2016). Our hypothesis is that looking at the (gradual) emergence of verbal means of aggression (approximated by this kind of compound) might help illuminate the initial steps of the language evolution/self-domestication feedback loop. These verbal items would have afforded an adaptive (non-violent) way to compete for status and sex, first by derogating existing rivals and placing prospective rivals on notice; and second by demonstrating verbal skills and quick wittedness, both directly relevant for sexual selection (Progovac and Locke, 2009, p. 346)4. As a consequence, they would have accelerated/reinforced the effects of selfdomestication on human behavior and cognition, promoting the transition to more complex forms of language. These types of verbal forms promise to make just a bit narrower the otherwise enormous chasm separating, on the one hand, expressions of emotion/aggression in animals, and, on the other hand, refined human language, with embedded sentences, and thousands of words expressing various subtleties of meaning. Code (2005, and references therein) offers evidence that swearwords are neurally distinct from the other words, relying both on brain areas where compositional language is processed, and on brain areas which support laughing and crying. In that sense, swearwords straddle the boundary between (animal) calls, which share many properties with laughing and crying, on the one hand, and compositional language, on the other. This reinforces the view that swearwords, which also often feature in insults, are primarily reactive, as are laughter and crying. Given that domestication processes can belong and protracted and not guaranteed to succeed either5, it is important that wecan identify factors that can reinforce it. According to our view, one of these factors was the gradual emergence of language itself (see also Sánchez- Villagra and van Schaik, 2019 for the importance of considering additional, synergistic factors, including language, in the considerations of self-domestication). For concreteness, we postulate that this feedback loop was particularly important during the time period roughly between 4 Sexual selection is also thought to be one important triggering factor of selfdomestication features, with females selecting less aggressive males, as discussed in section “Aggression, Verbal Behavior, and Sexual Selection.” 5 Künzl et al. (2003) found that long-term breeding and rearing of wild guinea pigs in captivity did not result in significant changes in behavior and hormonal stress responses in comparison to domestic guinea pigs. They concluded that it takes much longer periods of time, as well as artificial selection by humans, to bring about characteristics of domestication in wild animals. Human selfdomestication did not involve artificial selection by others, and as such is not expected to have been instantaneous. Similar processes of slow self-domestication have also been observed in bonobos (Hare et al., 2012). 200 and 50 kya6. This is a long time period when humans were not fully modern, neither in terms of their skull/brain morphology (and presumably, their cognitive abilities) and their behavior/culture nor in terms of their self-domestication (see Hare, 2017). During this time period, wepropose to correlate the advances in human self-domestication processes with the emergence of simple forms of language/syntax, which were particularly suitable for the expression of verbal aggression. The novelty of our approach lies in (1) giving an active role to early forms of language in interacting with self-domestication processes; (2) providing specific details and functions of this early stage of grammar (including insult and humor); (3) supplying neurobiological, ontogenetic, and clinical evidence of a link between (reactive) aggression and (reactive) verbal behavior; (4) identifying proxies of the earlier stages in evolution among cognitive disorders; and (5) identifying specific points of contact and mutual reinforcement between these two processes (self-domestication and early language evolution), including reduction in physical aggression and stress/tension, as well as sexual selection. One benefit of our proposal is that it helps solve the paradox of the two aggression types, reactive and proactive, which is raised by the Self-Domestication Hypothesis (SDH), that is, why proactive aggression has increased with time in spite of our increased self-domestication. The problem finds a direct solution in correlating early self-domestication processes with the emergence of simple forms of early language/grammar, featuring reactive verbal aggression; on the other hand, proactive aggression seems to be enabled in the later stages of self-domestication, which correlates with more complex forms of language (see Benítez-Burraco and Kempe, 2018; Kissel and Kim, 2019). The following stages outline our proposal (see also Figure 1): 1. The first stage, occurring roughly in the period prior to 200 kya, sees self-domestication processes only start to emerge, with reactive physical aggression still relatively high. 2. The second stage, occurring roughly from 200 to 50 kya, sees increased self-domestication favoring the emergence of early language forms with proto-grammars especially suitable for swearing and insult (i.e., reactive language), which began to gradually replace reactive physical aggression, serving the same function. This early language was insufficiently sophisticated to support proactive aggression. During this stage, there is an accelerated feedback loop between selfdomestication processes and the solidification of the early forms of language, both promoting a reduction in reactive physical aggression. 3. The third stage, 50–10kya (the Upper Paleolithic), saw selfdomestication reach its peak. More cooperation and socialization and less reactive aggression created a niche for more complex forms of language and cognition. 6 Pending further evidence, this timeline, especially the starting point, has to be considered approximate. As pointed out by a reviewer, researchers have proposed that some forms of language with grammar may have been in place as early as 500kya, based on the skeletal and genetic evidence from Neanderthals (e.g., Dediu and Levinson, 2013; see also Johansson, 2005; Zilhão, 2011). Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 5 December 2019 | Volume 10 | Article 2807 4. The fourth stage, from 10kya (the onset of the Neolithic period) to the present day, was characterized by even more complex language and cognition, which now affords the linguistic, cognitive, and cultural means (e.g., sophisticated weapons) for coordinating premediated, large-scale, proactive aggression7. Our proposal regarding what characterized the second stage with respect to self-domestication and language evolution establishes a middle ground between two opposite but influential views, those of Chomsky and colleagues vs. Dediu and colleagues. On the one hand, based on their view of syntax/grammar as an undecomposable/unnegotiable block, Berwick and Chomsky (2011, 2016, also previous work) proposed that language/syntax emerged suddenly and recently, in its full complexity, “just a bit over 50,000 years ago” (Chomsky, 2005), 7 However, the picture is a bit more complicated. While there is a clear overall trend toward evolving self-domestication features in humans, including less masculinized traits in men, Cieri et al. (2014) found that Neolithic humans exhibit more masculinized features compared to Upper Paleolithic humans, as well as compared to present-day hunter-gatherers, attributing the effect to the more hierarchical and man-dominated nature of agricultural societies, where women have less opportunity to exert their sexual selection preferences, as compared to relatively egalitarian hunter-gatherer societies (see section “Aggression, Verbal Behavior, and Sexual Selection” for further discussion of these issues within a sexual selection scenario). It is also possible that proactive aggression contributed to this development, as it brings about wars, creating a new environment where stronger, more aggressive males would have been favored by both natural and sexual selection. with no possibility for any simpler stages or precursors, or “some 70,000–100,000 years ago, and does not seem to have undergone modification since then” (Bolhuis et al., 2014). On the other hand, based on the comparative evidence among Homo heidelbergensis’ descendants, Dediu and Levinson (2013) proposed that language dates back to at least H. heidelbergensis, to some 500–400 kya, suggesting that Neanderthals and Denisovans might have even spoken complex languages comparable to those of modern humans, which would imply hierarchical and recursive syntax. We therefore acknowledge that our proposed timelines may besubject to revision pending further evidence. By contrast, in our proposal, this time period (roughly 200–50 kya) was characterized by a pre-hierarchical stage of languages, to contrast with the hierarchical and recursive stage, which is often associated with Chomsky’s notion of Merge. To avoid potential terminological confusion, wewill adopt the terms pre-hierarchical stage and hierarchical stage. While the pre-hierarchical stage is associated with rudimentary symmetrical, flat, and non-recursive grammars, the hierarchical stage is associated with the exact opposite: asymmetrical, hierarchical, (potentially) recursive syntax. Nonetheless, as will be discussed in the following section, there is continuity and common ground between the two types of grammar, with the pre-hierarchical stage directly foreshadowing the nature of the hierarchical stage itself. Relevant to this debate is also the nature and significant degree of cross-linguistic variation attested in the expression FIGURE1 | A graphical summary of the hypothesis of how languages might have changed with time in our species under the effect of our self-domestication. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 6 December 2019 | Volume 10 | Article 2807 of the hierarchical stage (e.g., transitivity and tense) among extant human languages. Considering this variation in detail led to the proposal that these widely diverging hierarchical solutions were a later add-on, superimposed upon the common proto-syntactic foundation, and that the hierarchical layers of language may not have emerged only once and uniformly (in Africa) along with our species, but instead multiple times, and independently, either within Africa, or after the dispersion from Africa, plausibly in response to cultural pressures and innovations (Progovac, 2015, 2016)8. At least under the uniregional view of human origins, this would argue against hierarchical syntax emerging earlier than around 100–50 kya with humans9. EMERGENCE OF PROTO-SYNTAX AND VERBAL AGGRESSION (INSULT) The use of profanity is characterized as “reactive language” (Bergen, 2016, p.88) in the sense that it is typically impulsive and spontaneous, often referred to as automatic speech, or automatisms in aphasic studies (e.g., Jackson, 1884; Code, 2011). It contrasts with “intentional” language, which gets impaired in Broca’s and global aphasias and which is more complex, demanding greater working memory. Wecontend that reactive language (e.g., swearing) is continuous with reactive physical aggression, having gradually replaced the latter, during the second stage (roughly from 200 to 50 kya). Consider the following verb-noun compounds (1–3) from English, Serbian, and Twi, collected from various sources, old and new (English and Serbian examples are from Progovac, 2015; Twi examples are from Kingsley Okai, p.c., 2011)10. This type of compound is found across a variety of related and unrelated languages, with similar imagery across cultures (for 8 According to, e.g., Stringer (2007) and Finlayson (2009), there are still many uncertainties about human timeline and dispersals. Stringer (2007, p. 17) mentions a possibility for an African version of multiregionalism, citing “growing molecular evidence of deep divisions within African populations” (see also Wong, 2017 for some recent findings). Under this scenario, hierarchical syntax could have emerged much earlier, independently among different populations in Africa, more in line with Dediu and Levinson’s (2013) view. 9 It is of note that Chomsky (2005) has also advocated a rather late emergence of hierarchical syntax, around 50kya, as pointed out in the text. The difference is that on his approach syntax emerged suddenly in all its complexity, and uniformly, without any precursors, while on our approach syntax evolved gradually, and often differently in different populations, with precursors that interacted with the domestication and other processes involving the evolution of the brain. Also, for Chomsky, the evolution of syntax was fully biological/ genetic, while in our view, it involves a complex feedback loop between culture and genes. 10 Weekley (1916) collected a sizeable number of English verb-noun compounds. According to him, this expressive way of naming, often exhibiting unquotable coarseness, flourished in thirteenth and fourteenth centuries, yielding thousands of tokens. Mihajlović (1992) collected over 500 Serbian people and place names in this form, reporting that these condensed compositions pack in them “frozen fairy tales, proverbs, and ancient wisdoms and metaphors” (Mihajlović 1992, p. 8,9). Darmesteter (1934, p. 443) was impressed by the “artistic beauty and richness” of such derogatory compounds in French. specific examples and further references, see Progovac, 2015)11. It is of note that compounds like these have transient lives – they get created, and then the vast majority of them get abandoned, with only few surviving. As a result, different generations of speakers will befamiliar with different compounds on these lists, taken directly from Progovac (2016, p.8; further data can befound in Progovac and Locke, 2009 and Progovac, 2015). The significance of these compounds is also that they specialize for insult when referring to humans, in a variety of languages, reinforcing our view that simplest grammars are especially suitable for insult. There is no other grammatical strategy that we are aware of that specializes for insult, and certainly not a strategy with so many tokens. 1. kill-joy, turn-skin (traitor), hunch-back, wag-tail, tattle-tale, scatter-brain, cut-throat, cry-baby, fill-belly (glutton), crakebone (crack-bone), fuck-ass, fuck-head 2. cepi-dlaka “split-hair” (hair-splitter); guli-koža “peel-skin” (who rips you off); vrti-guz “spin-butt” (restless person, fidget); muti-voda “muddy-water” (trouble-maker); jebi-vetar “fuck-wind” (charlatan); vuci-guz “drag-butt” (slow-moving person); kosi-noga “skew-leg” (person who limps); podvi-rep “fold-tail” (one who is crestfallen); liz-guz “lick-butt”; poj-kurić “sing-dick” (womanizer) 3. Atoto-botom “dip-pocket” (pickpocket); kukru-bin “roll-dung” (beetle); nom-mmogya “suck-blood” (vampire); wodi-nii “kill-person” (killer) These creations specialize for derogatory reference and can bequite obscene and cruel. They are also humorous and creative, especially considering the simplicity of their structure. These compounds are coined by one single (non-recursive) operation merging just one verb and one noun (for illustration, see below; for further evidence and a discussion of alternative views, and possible variation across languages, see Progovac, 2015, 2019). Predominating among them are concrete, basic nouns, and verbs, depicting body parts and functions12. However, this rudimentary compounding strategy can produce stunning new concepts, often abstract. Their high imageability and coarseness contribute to the strong visceral effect. As metaphors, they demonstrate the cognitive innovations important for language, in particular, our ability to transcend the signature limits of core knowledge systems 11 Contrary to Nóbrega and Miyagawa (2015)’s view, in order for such compounds to count as approximations (“fossils”) of early stages of syntax, they do not necessarily need to be found in every human language, with exactly the same characteristics (Progovac, 2019 offers a detailed defense of syntactic “fossils” in this sense). The claim is that this is the starting point, the bedrock upon which one can build (or not) various types of syntactic complexity, as discussed below. Different languages in fact offer different types of fossil structures in this sense, some of them rare to find across modern languages (as discussed by Progovac, 2015). 12 See also Samarin (1969) for Gbeya insults, which also fixate on body parts and physical appearance. In fact, Mohr (2013) provides evidence that such vulgar expressions were completely appropriate to use in, e.g., Roman times, only 2 kya, clearly at the stage of advanced modernity. As she argues, the appropriateness of such language coincided with a much less strict sense of privacy in performing bodily functions, as well as in covering body parts with clothing. Whatever we might think of such language today, it played a much bigger role in ancient times. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 7 December 2019 | Volume 10 | Article 2807 and ultimately, to combine and unify conceptual units that belong to distinct domains (see Boeckx and Benítez-Burraco, 2014a for discussion). This enables us to metaphorize and metonymize, as well as to grammaticalize, and ultimately, to make languages change (see Benítez-Burraco, 2017 for discussion). They are thus also directly relevant for the consideration of cross-modality in the evolution of language, as discussed by, e.g., Cuskley and Kirby (2013) and Miyagawa et al. (2018). These compounds exhibit features consistent with the primitive stages of language: grammatical simplicity; basic, concrete vocabulary; strong visceral effect; significant creativity; ability to transcend modalities to create new, abstract concepts (metaphoricity); ability to entertain and amuse (including humor); and continuity with complex syntax (see below). While these creations cannot be completely identical to what was created early in evolution13, they can serve as excellent proxies, or approximations, which can be used to test current hypotheses, as well as to formulate new ones. Moreover, even though they certainly fall short of modern syntactic riches, they provide the foundation, the template from which to build modern syntaxes, as discussed below. As argued by, e.g., Gil (2005), such simple (associational) grammars are sufficient for many practical purposes. While it is hard not to be distracted (or disturbed) by their extraordinary content, it is necessary to focus on the grammatical properties of these compounds. It is because of the most rudimentary nature of their grammar that these compounds qualify as approximations/proxies of proto-syntax. One concrete consequence of this type of two-slot grammar (which can only fit one verb and one noun, e.g., turn-skin) is that it cannot depict transitive events, which would require (at least) three slots (e.g., *snake-turn-skin; or *snake-shed-skin). In fact, this type of grammar is incapable of distinguishing subjects from objects (for further evidence, see Progovac, 2015). The noun in these compounds can beeither subject-like (cry-baby; rattle-snake; turn-table; tumbleweed) or object-like (turn-coat/skin; tumble-dung (beetle); fold-tail; split-hair), and sometimes, it is hard to tell (e.g., scatter-brain; busy-body; dare-devil). Moreover, unlike their hierarchical counterparts in (4), verb-noun compounds in English (or Serbian) are not recursive (5), in the sense that the output of one binary operation of V + N (creating another N, pick-pocket) cannot serve as input to another binary operation, combining, e.g., the verb (V) chase with the noun (N) pick-pocket. 4. truck-driver chaser (the one who chases those who drive trucks) 5. *chase-pick-pocket (the one who chases those who pick pockets) This simple binary stage of language directly foreshadows the nature of modern grammars in two important respects. First, modern grammars (with their so-called Merge operation) are considered to bebinary, too, creating structures in a pairwise fashion. Second, modern grammars rely heavily on nouns and verbs to express predications, i.e., who (noun) does what 13 For example, while in modern languages, the categories of verbs and nouns are typically distinguished grammatically, this would not have been the case at the time when grammar/language just started emerging. (verb). One can certainly imagine different kinds of grammars (ternary, n-ary), and different vocabularies depicting totally different concepts and relations, but modern human grammars are designed in a painstakingly binary fashion, and mostly for the purposes of expressing who does what (to whom). Such noun-verb combinations are at the bottom and the beginning of almost every modern sentence14. In fact, syntactic theory (e.g., Minimalism and predecessors) considers that every sentence unfolds from this bottom layer, which typically features a merge of just one verb and one noun (phrase), resulting in a Verb Phrase (VP) or Small Clause (SC), as given in (6). This analysis of the modern sentence is one of the most insightful and stable postulates in this theoretical framework. It was originally outlined by Burzio (1981), Stowell (1981), and Kitagawa (1985) and further solidified in the work of Koopman and Sportiche (1991), Chomsky (1995), Adger (2003), Citko (2011), and many others. This merge operation at the bottom of the hierarchy is sometimes referred to as First Merge in syntactic literature (e.g., Adger, 2003), whereas Second Merge adds a second argument (subject), in another, higher layer/segment of the verb phrase, which may be referred to as little vP (where TP is the Tense Phrase, responsible for the expression of tense and finiteness): 6. TP > vP > SC/VP15 If one intends to express both a subject and an object, together with the verb (7), one cannot do so with just a single binary operation (note that human grammars do not seem to allow ternary merges, but only binary ones; e.g., Kayne, 1984). This now requires first assembling an intransitive verb phrase or VP (a verb and one noun) (8a), and then taking that VP as an assembled unit and merging it with another layer of structure, little vP (8b). And the same is true for expressing tense/time – yet another layer, TP, is added for that purpose (8c). But, importantly, at the bottom of both transitive (7,8) and intransitive (9,10) sentences lies the binary, and possibly flat, small clause combination of just one verb and one noun (phrase)16. 7. Petra will rattle snakes. 8. a. [SC/VP rattle snakes] → b. [vP Petra [SC/VP rattle snakes]] → c. [TP Petra will [vP Petra [SC/VP rattle snakes]]] 14 It is also of note that Heine and Kuteva (2007) reconstructed a stage of human language evolution in which only nouns were used, followed by a stage in which both nouns and verbs were used, but no other categories, arguing that other categories gradually gammaticalize from nouns and verbs. 15 The representation in (6) depicts the basic (partial) hierarchy of sentential structure, widely adopted in this syntactic framework. These are the least controversial layers, sufficient for our purposes, but there are certainly several others that have been postulated (see, e.g., Adger, 2003). 16 It is of note that in some cases what counts as subject vs. object can get blurred, depending not so much on the noun’s inherent relationship with the verb, but more on whether or not there are additional noun arguments. This is the case with the noun snake in the two derivations in the text. This is relevant for the claim that this bottom layer by itself is not capable of distinguishing subjects from objects. The reader should also note that these derivations are simplified by omitting certain steps and null categories (such as null v head), which are not relevant for the discussion. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 8 December 2019 | Volume 10 | Article 2807 9. Snakes will rattle./Petra will rattle. 10. a. [SC/VP rattle snakes] → [SC/VP rattle Petra] → b. [TP Snakes will [SC/VP rattle snakes]] [TP Petra will [SC/VP rattle Petra]] The cross-out notation indicates the initial, underlying position of the subject in the small clause, before it moves to the TP layer. The Move operation in modern syntax can be seen as a strategy for connecting various layers of structure and, in this case, transforming the ancestral small clause into a full-fledged modern sentence. This certainly looks like a tortured, roundabout way to simply express who does what to whom. But this stepby-step building of modern syntactic layers, including transitivity, makes perfect sense if the original proto-grammar was preserved as the foundation upon which to build further layers, rather than discarded. It would have been a solid, sturdy step from which to reach for ever higher but shakier steps. The less plausible alternative would have been to step down first, to the platform with no grammar at all, and then start from scratch, trying to jump straight to the higher realms. But this would have resulted in very different modern grammars17. It is this binary requirement on building syntactic structure, already foreshadowed in the proto-grammar stage, that forces the hierarchy/asymmetry, which characterizes modern languages. Even though our focus here is on verbal aggression and insult, the benefits of this kind of proto-grammar would have been much broader. This type of proto-grammar would have also provided a convenient strategy for naming animals [tumbledung; swish-tail (bird); stink-bug], plants (tumble-weed; catch-fly), objects, and places, as well as for expressing basic commands (e.g., Catch fly! Turn snake!) and statements (e.g., Bug stink; Monkey see), not to mention enhanced ways of thinking, because it enables one to create new concepts by merging two pre-existing concepts. They could have also been used for affective purposes between partners or for calming and comforting one’s children (e.g., Baby sleep), also contributing to alleviating stress and tensions. In addition, according to Progovac (2015, 2016), an important extension of this two-word proto-grammar would have been two-clause symmetric combinations involving binary formulae (typically AB AC), often expressing wisdoms and observations (e.g., You seek, you find; You sow, you reap; Easy come, easy go; Come one, come all; First come, first serve(d); Like father, like son; Monkey see, monkey do)18. Such symmetric/ paratactic clause combinations, where clauses stand next to each other, would have foreshadowed modern-day subordination/ hypotaxis, where clauses get embedded one within another (e.g., Those who seek will find.). 17 One possibility would ben-ary (as opposed to binary) grammars, with certain designated slots with fixed ordering for tense, subject, verb, object, without grouping these categories into constituents and subconstituents, and without some of these categories exhibiting syntactic dominance over the others. One can also imagine languages that are not obsessed with who does what to whom. There seems to be nothing inevitable about evolving grammars with binary branching based on predication typically expressed by verbs and nouns. 18 Such expressions are preserved much better in some languages than others (see Progovac, 2015, 2016 for discussion and references.) For a more theoretical discussion of the relevance of symmetry vs. asymmetry in human language and evolution, see also Citko (2011) and Progovac (2015). In summary, the postulated approximations of proto-grammar provide continuity with modern syntax in two essential ways: (1) in their binary nature and (2) in their reliance on noun-like and verb-like elements to express predication. Even though it has become customary to reduce syntax to Chomsky’s Merge, it is important to emphasize here that the combinatorics of syntax is just one aspect of it, determining how many elements can merge at a time (binarity), and how many times (recursion), and in which manner (flat or hierarchical). Human syntax/language is also undoubtedly designed to express predication, i.e., to express who does what (to whom), by using primarily verbs and nouns. Importantly, the way syntax became complex is not in just any old random way, but in a way that helps express, with more precision, who does what to whom (and when, and where, and how, and why)19. In both of these respects (binary combinatorics, and the focus on who does what to whom), verb-noun compounds are an excellent stepping stone into modern syntax. Importantly for our purposes, the proto-grammar strategy behind these compounds not only provides continuity with complex syntax but also provides a more graceful transition from animal cognition, and particularly, from animal behavior, i.e., their emotional vocalizations, to human behavior, via verbal aggression. NEUROBIOLOGY OF PHYSICAL AGGRESSION AND REACTIVE LANGUAGE The limbic system (a group of brain structures supporting emotion, motivation, and long-term memory; see Rolls, 2015 for review), the striatal regions, and parts of the cortex, particularly, the frontal and the temporal cortices (Dolan etal., 2002; Yang etal., 2009; Boccardi et al., 2011) support aggressive behavior. Highly aggressive subjects exhibit enlargement and atypical activation of striatal regions (particularly, the caudate; Gatzke-Kopp et al., 2009; Ducharme et al., 2012; Yang et al., 2017). The striatum has been associated with the dopamine system that governs the regulation of motivated behavior (Mogenson et al., 1980), and which is critically involved in the expression of aggression in animals (Rodriguiz et al., 2004), but it is also crucially involved in language processing (e.g., Krishnan etal., 2016; Viñas-Guasch and Wu, 2017). Domesticated rats exhibit size reductions of the striatal area (Kruska and Schott, 1977), and the limbic system exhibits the highest differences between domesticated animals and their wild conspecifics (reviewed by Kruska, 1988). Similar brain areas are involved in both reactive and proactive aggression; however, only the latter is associated with a thinner anterior cingulate cortex (Yang et al., 2017), a region involved 19 This is in fact where languages differ profoundly. There are several different strategies for discriminating between subjects/agents from objects/patients, including, but not limited to, ergative-absolutive grammars, split-ergative grammars, nominative-accusative grammars, serial verb grammars, and activestative grammars. These strategies are distinct enough to pose serious challenges for linguistic analysis and description. In this approach, the emergence of transitivity is seen as a later evolutionary development, discovering different solutions to the same problem posed by the limitations of the most rudimentary of grammars. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 9 December 2019 | Volume 10 | Article 2807 in the regulation of emotions and social behavior including conflict monitoring and empathy (Devinsky etal., 1995; Botvinick, 2007). The cingulate gyrus, which is part of cingulate cortex, plays a key role in language processing, contributing to speech production via its connections with Broca’s area (Bernal etal., 2015). Compared to chimpanzees, bonobos (who are less aggressive) exhibit stronger links between the anterior cingulate gyrus and the amygdala, a pathway involved in the inhibition of aggression (Rilling et al., 2012). Likewise, Roth and Strüber (2009) found that reactive aggression is associated with smaller, less active frontal brain structures and amygdala hyperactivity, whereas proactive aggression correlates with reduced response of the amygdala and of cortical regions related to empathic and social behavior. Compared to chimps, bonobos also show an enlarged dorsal amygdala (Rilling et al., 2012). The amygdala is also implicated in the activation of the hypothalamic-pituitary-adrenal (HPA) axis through connections with the hypothalamus (Davis, 1997; Ledoux, 1998). The HPA axis is a major neuroendocrine system encompassing the hypothalamus, the pituitary gland, and the adrenal glands and regulating a great number of bodily functions. A reduced response of the HPA axis to stress has been observed in most domesticated animals (Kruska, 1988; Künzl and Sachser, 1999; Trut et al., 2009). With respect to aggression and cognitive functioning, reactive aggression in humans is associated with lower levels of goal-oriented inhibition and higher levels of flexibility, and proactive aggression is associated with higher levels of working memory (Hecht and Latzman, 2018)20. In comparison to other forms of language, the processing of swear words/profanity entails more involvement of the basal ganglia, limbic structures, thalamus, and the right hemisphere (e.g., Code, 2005, 2011; Bergen, 2016). The basal ganglia (i.e., the striatal regions) and the limbic system are also highly implicated in physical aggression. Disorders, which result in uncontrolled swearing/profanity, typically involve a basal-limbic connection dysfunction (discussed further in section “Disorders”). Basal-limbic structures are phylogenetically old, and the aspects of human communication associated with them are considered to beancient, too (Van Lancker and Cummings, 1999; Bradshaw, 2001; Bergen, 2016), a potentially controversial claim (although see also Lieberman, 2000, 2009 on the ancient nature of basal ganglia). In this respect, Code (2005, p.317) suggests that these forms of language might represent fossilized clues to the evolutionary origins of human communication. With brain damage affecting inhibitory processes, primitive behaviors (e.g., verbal automatisms) can emerge from primitive regions. In fact, damage to language centers in the brain can obliterate most language but leave swearing and expletives intact (see section “Disorders” for more details). 20 In this respect, Wynn and Coolidge (2004) proposed that working memory may have been enhanced in modern humans, compared to Neanderthals, contributing to the capacity for innovation and experimentation. It is also pointed out by Balari et al. (2013) that enhanced working memory may have enabled recursive syntax. Finally, Benítez-Burraco and Kempe (2018) linked the enhancement of working memory to the emergence of languages with expanded vocabularies and more complex syntax, which are purportedly optimized for conveying complex meanings and know-hows to people not sharing a common ground or a common cultural knowledge. Differential impairment of reactive language versus intentional language implies that they employ distinct neural bases/pathways (Bergen, 2016, p.87). The circuit that supports reactive language (including profanity) is evolutionarily far older, dominated by the limbic system, responsible for generating emotions and motor impulses, where the basal ganglia regulates and selectively suppresses such impulses (Bergen, 2016, p. 95). In disorders, such as Tourette’s syndrome with coprolalia, there is a failure of this regulatory function of basal ganglia (see section “Disorders”). The relevance of basal ganglia for emotional speech processes, including such basic emotions as fear and disgust, is also established in the work of Paulmann et al. (2009) and Péron et al. (2013). Emotional vocalizations by other primates and mammals also seem to be supported by this kind of pathway, involving the limbic system and the basal ganglia (Robinson, 1967; see also Gruber and Grandjean, 2017), suggesting that emotional, profane language has some continuity with emotional vocalizations in other animals. In natural use, expletives, especially those that are highly taboo, elicit strong physiological responses (including increased heart rate and sweating; Bergen, 2016). Such words are used for fundamental expression of deep emotion, including fear, pain, frustration, as well as for sex and violence (Code, 2005). The use of profanity is more common in men than in women (Jay, 1980, 1995; Van Lancker and Cummings, 1999, but see section “Aggression, Verbal Behavior, and Sexual Selection” for a possible challenge to this view), and this is true even in language disorders (Code, 1982, 2011; Jankovic and Rohaidy, 1987; Bergen, 2016). Considering that reactive physical aggression is more frequent in men than in women and that self-domestication was primarily subject to sexual selection (see section “Child Development”), this parallelism between physical and verbal aggression reinforces our hypothesis that verbal aggression acts as a proxy/replacement for reactive physical aggression. Finally, expletive compounds can be highly humorous. One of the main functions of humor is to provide relief from stress and tension, via laughter and mirth (Berlyne, 1972; Meyer, 2000; Buijzen and Valkenburg, 2004). Humor serves as a natural stress antagonist in situations of trauma and stress, by decreasing cortisol levels (Vrticka et al., 2013; Bains et al., 2014). Typically, wild animals exhibit a more pronounced cortisol response to stress, compared to their domestic counterparts (Künzl and Sachser, 1999; Künzl et al., 2003; Zipser et al., 2014; Kaiser et al., 2015). As noted above, domestication is associated with a reduction in the function of the HPA axis (Naumenko and Belyaev, 1980; Kruska, 1988; Oskina, 1996; Künzl and Sachser, 1999; Trut etal., 2009). Humor engages a core network of cortical and subcortical structures, including the meso-cortico-limbic dopaminergic system and the amygdala (Vrticka et al., 2013). In addition, humor can often serve as a form of strong assertiveness bordering on aggression, especially in cases of teasing and insult (see section “Child Development”). We therefore argue that humor’s dual functions (i.e., stress reduction function and verbal aggression), and its reliance on limbic structures supports our proposition that early forms of language provided relief from stress and tension, as well as a (verbal) alternative to reactive aggression, and thus reinforced the effects of self-domestication. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 16 December 2019 | Volume 10 | Article 2807 Boccardi, M., Frisoni, G. B., Hare, R. D., Cavedo, E., Najt, P., Pievani, M., et al. (2011). Cortex and amygdala morphology in psychopathy. Psychiatry Res. 193, 85–92. doi: 10.1016/j.pscychresns.2010.12.013 Boeckx, C., and Benítez-Burraco, A. (2014a). The shape of the human languageready brain. Front. Psychol. 5:282. doi: 10.3389/fpsyg.2014.00282 Boeckx, C., and Benítez-Burraco, A. (2014b). Globularity and language-readiness: generating new predictions by expanding the set of genes of interest. Front. Psychol. 5:1324. doi: 10.3389/fpsyg.2014.01324 Bolhuis, J. J., Tattersall, I., Chomsky, N., and Berwick, R. C. (2014). How could language have evolved? PLoS Biol. 12:e1001934. doi: 10.1371/journal. pbio.1001934 Boothroyd, L. G., Gray, A. W., Headland, T. N., Uehara, R. T., Waynforth, D., Burt, D. M., et al. (2017). Male facial appearance and offspring mortality in two traditional societies. PLoS One 12:e0169181. doi: 10.1371/journal. pone.0169181 Botvinick, M. M. (2007). Conflict monitoring and decision making: reconciling two perspectives on anterior cingulate function. Cogn. Affect. Behav. Neurosci. 7, 356–366. doi: 10.3758/CABN.7.4.356 Bradshaw, J. L. (2001). Developmental disorders of the frontostriatal system. Hove: Psychology Press. Brunner, R. J., Kornhuber, H. H., Seemuller, E., Suger, G., and Wallesch, C.-W. (1982). Basal ganglia participation in language pathology. Brain Lang. 16, 281–299. doi: 10.1016/0093-934X(82)90087-6 Budman, C., Coffey, B. J., Shechter, R., Schrock, M., Wieland, N., Spirgel, A., et al. (2008). Aripiprazole in children and adolescents with Tourette disorder with and without explosive outbursts. J. Child Adolesc. Psychopharmacol. 18, 509–515. doi: 10.1089/cap.2007.061 Buijzen, M., and Valkenburg, P. M. (2004). Developing a typology of humor in audiovisual media. Media Psychol. 6, 147–167. doi: 10.1207/s1532785xmep0602_2 Burnham, T. C. (2007). High-testosterone men reject low ultimatum game offers. Proc. R. Soc. B Biol. Sci. 274, 2327–2330. doi: 10.1098/rspb.2007.0546 Burzio, L. (1981). Intransitive verbs and Italian auxiliaries. PhD dissertation. Cambridge (MA): Institute of Technology. Cahana-Amitay, D., Albert, M. L., Pyun, S.-B., Westwood, A., Jenkins, T., Wolford, S., et al. (2011). Language as stressor in aphasia. Aphasiology 25, 593–614. doi: 10.1080/02687038.2010.541469 Card, N. A., Stucky, B. D., Sawalani, G. M., and Little, T. D. (2008). Direct and indirect aggression during childhood and adolescence: a meta-analytic review of gender differences, intercorrelations, and relations to maladjustment. Child Dev. 79, 1185–1229. doi: 10.1111/j.1467-8624.2008.01184.x Chappell, P., Riddle, M., Anderson, G., Scahill, L., Hardin, M., Walker, D., et al. (1994). Enhanced stress responsivity of Tourette syndrome patients undergoing lumbar puncture. Biol. Psychiatry. 36, 35–43. Chen, K., Budman, C. L., Diego Herrera, L., Witkin, J. E., Weiss, N. T., Lowe, T. L., et al. (2013). Prevalence and clinical correlates of explosive outbursts in Tourette syndrome. Psychiatry Res. 205, 269–275. doi: 10.1016/j. psychres.2012.09.029 Choi, J.-K., and Bowles, S. (2007). The coevolution of parochial altruism and war. Science 318, 636–640. doi: 10.1126/science.1144237 Chomsky, N. (1995). The minimalist program. Cambridge, MA: MIT Press. Chomsky, N. (2005). Three factors in language design. Linguist. Inq. 36, 1–22. doi: 10.1162/0024389052993655 Chomsky, N. (2017). The language capacity: architecture and evolution. Psychon. Bull. Rev. 24, 200–203. doi: 10.3758/s13423-016-1078-6 Churchill, S. E. (2014). Thin on the ground: Neandertal biology, archeology, and ecology. London: Wiley-Blackwell. Cieri, R. L., Churchill, S. E., Franciscus, R. G., Tan, J., and Hare, B. (2014). Craniofacial feminization, social tolerance, and the origins of behavioral modernity. Curr. Anthropol. 55, 419–443. doi: 10.1086/677209 Citko, B. (2011). Symmetry in syntax: Merge, move, and labels. Cambridge: Cambridge University Press. Clark, E., Hecht, B. F., and Mulford, R. C. (1986). Coining complex compounds in English: affixes and word order in acquisition. Linguistics 24, 7–29. Clarke, E., and Heyes, C. (2017). The swashbuckling anthropologist: Henrich on the secret of our success. Biol. Philos. 32, 289–305. doi: 10.1007/ s10539-016-9554-y Code, C. (1982). Neurolinguistic analysis of recurrent utterances in aphasia. Cortex 18, 141–152. doi: 10.1016/S0010-9452(82)80025-7 Code, C. (1987). Language, aphasia, and the right hemispher. London: Wiley. Code, C. (2005). First in, last out? The evolution of aphasic lexical speech automatisms to agrammatism and the evolution of human communication. Interact. Stud. 6, 311–334. doi: 10.1075/is.6.2.08cod Code, C. (2011). Nonfluent aphasia and the evolution of proto-language. J. Neurolinguistics 24, 136–144. doi: 10.1016/j.jneuroling.2009.12.007 Code, C., Tree, J., and Dawe, K. (2009). Opportunities to say ‘yes’: rare speech automatisms in a case of progressive nonfluent aphasia and apraxia. Neurocase 15, 445–458. doi: 10.1080/13554790902911634 Cohen, A. J., and Leckman, J. F. (1992). Sensory phenomena associated with Gilles de la Tourette’s syndrome. J. Clin. Psychiatry 53, 319–323. Corbett, B. A., Mendoza, S. P., Baym, C. L., Bunge, S. A., and Levine, S. (2008). Examining cortisol rhythmicity and responsivity to stress in children with Tourette syndrome. Psychoneuroendocrinology 33, 810–820. doi: 10.1016/j. psyneuen.2008.03.014 Crockett, M. J., Clark, L., Hauser, M. D., and Robbins, T. W. (2010). Serotonin selectively influences moral judgment and behavior through effects on harm aversion. PNAS 107, 17433–17438. doi: 10.1073/pnas.1009396107 Cuskley, C., and Kirby, S. (2013). “Synesthesia, cross-modality, and language evolution” in Oxford handbook of synesthesia. eds. J. Simner and E. Hubbard (Oxford, UK: Oxford Handbooks Online). Darmesteter, A. (1934). A historical French Grammar. London: Macmillan and Co. Authorized English edition by Alphonse Hartog. First edition in 1899. Davis, M. (1997). Neurobiology of fear responses: the role of the amygdala. J. Neuropsychiatr. Clin. Neurosci. 9, 382–402. doi: 10.1176/jnp.9.3.382 Deacon, T. W. (2003). “Multilevel selection in a complex adaptive system: the problem of language origins” in Evolution and learning: The Baldwin effect reconsidered. A Bradford book. eds. W. H. Bruce and D. J. Depew (Cambridge, MA: The MIT Press), 81–106. Dediu, D. (2015). An introduction to genetics for language scientists. Cambridge: Cambridge University Press. Dediu, D., and Levinson, S. C. (2013). On the antiquity of language: the reinterpretation of Neandertal linguistic capacities and its consequences. Front. Psychol. 4:397. doi: 10.3389/fpsyg.2013.00397 Devinsky, O., Morrell, M. J., and Vogt, B. A. (1995). Contributions of anterior cingulate cortex to behaviour. Brain 118, 279–306. doi: 10.1093/brain/118.1.279 Dolan, M., Deakin, W. J., Roberts, N., and Anderson, I. (2002). Serotonergic and cognitive impairment in impulsive aggressive personality disordered offenders: are there implications for treatment? Psychol. Med. 32, 105–117. doi: 10.1017/S0033291701004688 Ducharme, S., Hudziak, J. J., Botteron, K. N., Albaugh, M. D., Nguyen, T. V., Karama, S., et al. (2012). Decreased regional cortical thickness and thinning rate are associated with inattention symptoms in healthy children. J. Am. Acad. Child Adolesc. Psychiatry 51, 18–27.e12. doi: 10.1016/j.jaac.2011.09.022 Evers, R. A., and van de Wetering, B. J. (1994). A treatment model for motor tics based on a specific tension-reduction technique. J. Behav. Ther. Exp. Psychiatry 25, 255–260. doi: 10.1016/0005-7916(94)90026-4 Finlayson, C. (2009). The humans who went extinct: Why Neanderthals died out and we survived. Oxford: Oxford University Press. Franks, B., and Rigby, K. (2005). “Deception and mate selection: some implications for relevance and the evolution of language” in Language origins: Perspectives on evolution. Studies in the evolution of language. ed. M. Tallerman (Oxford: Oxford University Press), 208–229. Freeman, R. D., Zinner, S. H., Müller-Vahl, K. R., Fast, D. K., Burd, L. J., Kano, Y., et al. (2009). Coprophenomena in Tourette syndrome. Dev. Med. Child Neurol. 51, 218–227. doi: 10.1111/j.1469-8749.2008.03135.x Fukase, H., Kondo, O., and Ishida, H. (2015). Size and placement of developing anterior teeth in immature Neanderthal mandibles from Dederiyeh cave, Syria: implications for emergence of the modern human chin. Am. J. Phys. Anthropol. 156, 482–488. doi: 10.1002/ajpa.22665 Ganos, C., Münchau, A., and Bhatia, K. (2014). The semiology of tics, Tourette’s, and their associations. Mov. Disord. Clin. Pract. 1, 145–153. doi: 10.1002/ mdc3.12043 Ganos, C., Roessner, V., and Munchau, A. (2013). The functional anatomy of Gilles de la Tourette syndrome. Neurosci. Biobehav. Rev. 37, 1050–1062. doi: 10.1016/j.neubiorev.2012.11.004 Gatzke-Kopp, L. M., Beauchaine, T. P., Shannon, K. E., Chipman, J., Fleming, A. P., Crowell, S. E., et al. (2009). Neurological correlates of reward responding in adolescents with and without externalizing behavior disorders. J. Abnorm. Psychol. 118, 203–213. doi: 10.1037/a0014378 Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 17 December 2019 | Volume 10 | Article 2807 Gibson, G. (2009). Decanalization and the origin of complex disease. Nat. Rev. Genet. 10, 134–140. doi: 10.1038/nrg2502 Gil, D. (2005). “Isolating-monocategorial-associational language” in Handbook of categorizaton in cognitive science. eds. H. Cohen and C. Lefebvre (Amsterdam: Elsevier), 347–379. Gleeson, B. T. (2018). Masculinity and the mechanisms of human selfdomestication. BioRxiv [Preprint]. doi: 10.1101/143875 Gleeson, B. T., and Kushnick, G. (2018). Female status, food security, and stature sexual dimorphism: testing mate choice as a mechanism in human self-domestication. Am. J. Phys. Anthropol. 167, 458–469. doi: 10.1002/ ajpa.23642 Goldstein, K. (1942). Aftereffects of brain injuries in war: Their evaluation and treatment. New York: Grune & Stratto. Gossen, G. (1976). “Verbal dueling in Chamula” in Speech play: Research and resources for the study of linguistic creativity. ed. B. Kirshenblatt-Gimblett (Philadelphia: University of Pennsylvania Press), 21–46. Gruber, T., and Grandjean, D. (2017). A comparative neurological approach to emotional expressions in primate vocalizations. Neurosci. Biobehav. Rev. 73, 182–190. doi: 10.1016/j.neubiorev.2016.12.004 Haiman, J. (2013). “Decorative morphology in Kmer” in The aesthetics of grammar: Sound and meaning in the languages of mainland Southeast Asia. ed. J. P. Williams (Cambridge: Cambridge University Press), 61–82. Hare, B. (2017). Survival of the friendliest: Homo sapiens evolved via selection for prosociality. Annu. Rev. Psychol. 68, 24.1–24.32. doi: 10.1146/annurevpsych-010416-044201 Hare, B., Wobber, V., and Wrangham, R. (2012). The self-domestication hypothesis: evolution of bonobo psychology is due to selection against aggression. Anim. Behav. 83, 573–585. doi: 10.1016/j.anbehav.2011.12.007 Hecht, L. K., and Latzman, R. D. (2018). Exploring the differential associations between components of executive functioning and reactive and proactive aggression. J. Clin. Exp. Neuropsychol. 40, 62–74. doi: 10.1080/13803395. 2017.1314450 Heine, B., and Kuteva, T. (2007). The genesis of grammar. A reconstruction. Oxford: Oxford University Press. Herrmann, E., Hare, B., Cissewski, J., and Tomasello, M. A. (2011). Comparison of temperament in nonhuman apes and human infants. Dev. Sci. 14, 1393–1405. doi: 10.1111/j.1467-7687.2011.01082.x Hill, A. K., Bailey, D. H., and Puts, D. A. (2017). “Chapter 15 - gorillas in our midst? Human sexual dimorphism and contest competition in men” in On human nature. ed. F. J. Ayala (San Diego: Academic Press), 235–249. Hillert, D. (2014). The nature of language: Evolution, paradigms and circuits. New York: Springer. Jablonka, E., Ginsburg, S., and Dor, D. (2012). The co-evolution of language and emotions. Philos. Trans. R. Soc. B 367, 2152–2159. doi: 10.1098/rstb.2012.0117 Jackson, H. J. (1884). “Evolution and dissolution of the nervous system” in Selected writings of John Hughlings Jackson. Vol. 11, ed. J. Taylor (London: Staples Press). Jankovic, J. (1997). Tourette syndrome. Phenomenology and classification of tics. Neurol. Clin. 15, 267–275. doi: 10.1016/s0733-8619(05)70311-x Jankovic, J., and Rohaidy, H. (1987). Motor, behavioral and pharmacologic findings in Tourette’s syndrome. Can. J. Neurol. Sci. 14, 541–546. doi: 10.1017/ S0317167100038087 Jay, T. (1980). Sex roles and dirty word usage: a review of the literature and a reply to Haas. Psychol. Bull. 88, 614–621. doi: 10.1037/0033-2909.88.3.614 Jay, T. (1995). “Cursing: a damned persistent lexicon” in Basic and applied memory: Research on practical aspects of memory. eds. D. J. Hermann, M. K. Johnson, C. McEvoy, C. Hertzog, and P. Hertel (Hillsdale, NJ: Erlbaum). Johansson, S. (2005). Origins of language: Constraints on hypotheses. Amsterdam/ Philadelphia: John Benjamins. Kaiser, S., Hennessy, M. B., and Sachser, N. (2015). Domestication affects the structure, development and stability of biobehavioural profiles. Front. Zool. 12(Suppl. 1):S19. doi: 10.1186/1742-9994-12-S1-S19 Kano, Y., Ohta, M., Nagai, Y., Spector, I., and Budman, C. (2008). Rage attacks and aggressive symptoms in Japanese adolescents with Tourette syndrome. CNS Spectr. 13, 325–332. doi: 10.1017/S1092852900016448 Kayne, R. (1984). Connectedness and binary branching. Dordrecht: Foris. Kissel, M., and Kim, N. C. (2019). The emergence of human warfare: current perspectives. Am. J. Phys. Anthropol. 168(Suppl. 67), 141–163. doi: 10.1002/ ajpa.23751 Kitagawa, Y. (1985). Small but clausal. Chic. Linguist. Soc. 21, 210–220. Koopman, H., and Sportiche, D. (1991). The position of subjects. Lingua 85, 211–258. doi: 10.1016/0024-3841(91)90022-W Kraemer, M., Abrahamsson, M., and Sjostrom, A. (1999). The neonatal development of the light flash visual evoked potential. Doc. Ophthalmol. 99, 21–39. doi: 10.1023/A:1002414803226 Krishnan, S., Watkins, K. E., and Bishop, D. V. M. (2016). Neurobiological basis of language learning difficulties. Trends Cogn. Sci. 20, 701–714. doi: 10.1016/j.tics.2016.06.012 Kruger, D. J. (2006). Male facial masculinity influences attributions of personality and reproductive strategy. Pers. Relat. 13, 451–463. doi: 10.1111/j.1475- 6811.2006.00129.x Kruska, D. C. (1988). “Mammalian domestication and its effects on brain structure and behaviour” in Intelligence and evolutionary biology. eds. H. J. Jerison and I. Jerison (Berlin: Springer Verlag), 211–250. Kruska, D., and Schott, U. (1977). [Comparative-quantitative investigations of brains of wild and laboratory rats]. J. Hirnforsch. 18, 59–67. Kuepper, Y., Alexander, N., Osinsky, R., Mueller, E., Schmitz, A., Netter, P., et al. (2010). Aggression—interactions of serotonin and testosterone in healthy men and women. Behav. Brain Res. 206, 93–100. doi: 10.1016/j.bbr.2009.09.006 Künzl, C., Kaiser, S., Meier, E., and Sachser, N. (2003). Is a wild mammal kept and reared in captivity still a wild animal? Horm. Behav. 43, 186–196. doi: 10.1016/S0018-506X(02)00017-X Künzl, C., and Sachser, N. (1999). The behavioral endocrinology of domestication: a comparison between the domestic Guinea pig (Cavia aperea f. porcellus) and its wild ancestor, the cavy (Cavia aperea). Horm. Behav. 35, 28–37. doi: 10.1006/hbeh.1998.1493 Kwak, C., Dat Vuong, K., and Jankovic, J. (2003). Premonitory sensory phenomenon in Tourette’s syndrome. Mov. Disord. 18, 1530–1533. doi: 10.1002/mds.10618 Laures-Gore, J. S. (2012). Aphasia severity and salivary cortisol over time. Clin. Exp. Neuropsychol. 34, 489–496. doi: 10.1080/13803395.2012.658356 Laures-Gore, J., Heim, C. M., and Yu-Sheng, H. (2007). Assessing cortisol reactivity to a linguistic task as a marker of stress in individuals with lefthemisphere stroke and aphasia. J. Speech Lang. Hear. Res. 50, 493–507. doi: 10.1044/1092-4388(2007/034) Leach, H. M. (2003). Human domestication reconsidered. Curr. Anthropol. 44, 349–368. doi: 10.1086/368119 Leckman, J. F., Knorr, A. M., Rasmussen, A. M., and Cohen, D. J. (1991). Basal ganglia research and Tourette’s syndrome. Trends Neurosci. 14:94. doi: 10.1016/0166-2236(91)90066-4 Leckman, J. F., and Peterson, B. S. (1993). The pathogenesis of Tourette’s syndrome: epigenetic factors active in early CNS development. Biol. Psychiatry 34, 425–427. doi: 10.1016/0006-3223(93)90232-3 Ledoux, J. (1998). Fear and the brain: where have we been, and where are we going? Biol. Psychiatry 44, 1229–1233. doi: 10.1016/S0006-3223(98)00282-0 Lieberman, P. (2000). Human language and our reptilian brain: The subcortical bases of speech, syntax, and thought. Cambridge, MA: Harvard University Press. Lieberman, P. (2009). FOXP2 and human cognition. Cell 137, 801–802. doi: 10.1016/j.cell.2009.05.013 Lieberman, P. (2015). Language did not spring forth 100,000 years ago. PLoS Biol. 13:e1002064. doi: 10.1371/journal.pbio.1002064 Locke, J. L. (2008). Cost and complexity: selection in language and speech. J. Theor. Biol. 251, 640–652. doi: 10.1016/j.jtbi.2007.12.022 Locke, J. L. (2009). Evolutionary developmental linguistics: naturalization of the faculty of language. Lang. Sci. 31, 33–59. doi: 10.1016/j.langsci. 2007.09.008 Locke, J. L., and Bogin, B. (2006). Language and life history: a new perspective on the evolution and development of linguistic communication. Behav. Brain Sci. 29, 259–325. doi: 10.1017/S0140525X0600906X Lupyan, G., and Dale, R. (2010). Language structure is partly determined by social structure. PLoS One 5:e8559. doi: 10.1371/journal.pone.0008559 Luria, A. (1970). Traumatic aphasia: Its syndromes, psychology, and treatment. The Hague: Mouton. Márquez, S., Pagano, A. S., Delson, E., Lawson, W., and Laitman, J. T. (2014). The nasal complex of Neanderthals: an entry portal to their place in human ancestry. Anat. Rec. 297, 2121–2137. doi: 10.1002/ar.23040 Marsh, P. (1978). Aggro: The illusion of violence. London: Dent. McBrearty, S. (2007). “Down with the revolution” in Rethinking the human revolution: New behavioral and biological perspectives on the origin and Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 18 December 2019 | Volume 10 | Article 2807 dispersal of modern humans. eds. P. Mellars, K. Boyle, O. Bar-Yosef, and C. Stringer (Cambridge, UK: McDonald Institute for Archeological Research, University of Cambridge), 133–151. McBrearty, S., and Brooks, A. (2000). The revolution that wasn’t: a new interpretation of the origin of modern human behavior. J. Hum. Evol. 39, 453–563. doi: 10.1006/jhev.2000.0435 McGhee, P. E. (1976). Sex differences in children’s humor. J. Commun. 26, 176–189. doi: 10.1111/j.1460-2466.1976.tb01922.x Mellars, P. (2002). “Archeology and the origins of modern humans: European and African perspectives” in The speciation of modern Homo sapiens. ed. T. J. Crow (Oxford: Oxford University Press), 31–47. Mellars, P. (2007). “Introduction: rethinking the human revolution: Eurasian and African perspectives” in Rethinking the human revolution: New behavioral and bological perspectives on the origin and dispersal of modern humans. eds. P. Mellars, K. Boyle, O. Bar-Yosef, and C. Stringer (Cambridge, UK: McDonald Institute for Archeological Research, University of Cambridge), 1–11. Meyer, J. C. (2000). Humor as a double-edged sword: four functions of humor in communication. Commun. Theory 10, 310–331. doi: 10.1111/j.1468-2885.2000. tb00194.x Mihajlović, V. (1992). Ime po Zapovesti (Name by command). Beograd: Nolit. Miller, G. A. (2000). The mating mind: How sexual choice shaped the evolution of human nature. London: William Heinemann. Mink, J. W. (2003). The basal ganglia and involuntary movements: impaired inhibition of competing motor patterns. Arch. Neurol. 60, 1365–1368. doi: 10.1001/archneur.60.10.1365 Miranda, D. M., Wigg, K., Kabia, E. M., Feng, Y., Sandor, P., and Barr, C. L. (2009). Association of SLITRK1 to Gilles de la Tourette syndrome. Am. J. Med. Genet. B Neuropsychiatr. Genet. 150B, 483–486. doi: 10.1002/ajmg.b.30840 Miyagawa, S., Lesure, C., and Nóbrega, V. A. (2018). Cross-modality information transfer: a hypothesis about the relationship among prehistoric cave paintings, symbolic thinking, and the emergence of language. Front. Psychol. 9, 1–9. doi: 10.3389/fpsyg.2018.00115 Mogenson, G. J., Jones, D. L., and Yim, C. Y. (1980). From motivation to action: functional interface between the limbic system and the motor system. Prog. Neurobiol. 14, 69–97. doi: 10.1016/0301-0082(80)90018-0 Mohr, M. (2013). Holy shit: A brief history of swearing. Oxford: Oxford University Press. Montoya, E. R., Terburg, D., Bos, P. A., and van Honk, J. (2012). Testosterone, cortisol, and serotonin as key regulators of social aggression: a review and theoretical perspective. Motiv. Emot. 36, 65–73. doi: 10.1007/s11031-011-9264-3 Naumenko, E. V., and Belyaev, D. K. (1980). “Neuroendocrine mechanisms in animal domestication” in Problems in general genetics. Proceedings of the XIY international congress of genetics. Vol. 2, ed. D. K. Belyaev (Moscow: Mir), 12–24. Neubauer, S., Hublin, J.-J., and Gunz, P. (2018). The evolution of modern human brain shape. Sci. Adv. 4:eaao5961. doi: 10.1126/sciadv.aao5961 Nóbrega, V., and Miyagawa, S. (2015). The precedence of syntax in the rapid emergence of human language in evolution as defined by the integration hypothesis. Front. Psychol. 6:271. doi: 10.3389/fpsyg.2015.00271 Okanoya, K. (2015). Evolution of song complexity in Bengalese finches could mirror the emergence of human language. J. Ornithol. 156, 65–72. doi: 10.1007/s10336-015-1283-5 Oskina, I. (1996). Analysis of the functional state of the pituitary-adrenal axis during posnatal development of domesticated silver foxes. Scientifur 20, 159–167. Ozomaro, U., Cai, G., Kajiwara, Y., Yoon, S., Makarov, V., Delorme, R., et al. (2013). Characterization of SLITRK1 variation in obsessive-compulsive disorder. PLoS One 8:e70376. doi: 10.1371/journal.pone.0070376 Pagliai, V. (2009). The art of dueling with words: toward a new understanding of verbal duels across the world. Oral Tradit. 24, 61–88. doi: 10.1353/ort.0.0054 Patterson, F., and Gordon, W. (1993). “The case for the personhood of gorillas” in The great ape project. eds. P. Cavalieri and P. Singer (New York, NY: St. Martins Griffin), 58–77. Paulmann, S., Pell, M. D., and Kotz, S. A. (2009). Comparative processing of emotional prosody and semantics following basal ganglia infarcts: ERP evidence of selective impairments for disgust and fear. Brain Res. 1295, 159–169. doi: 10.1016/j.brainres.2009.07.102 Péron, J., Frühholz, S., Vérin, M., and Grandjean, D. (2013). Subthalamic nucleus: a key structure for emotional component synchronization in humans. Neurosci. Biobehav. Rev. 37, 358–373. doi: 10.1016/j.neubiorev.2013.01.001 Plavcan, J. M. (2012). Sexual size dimorphism, canine dimorphism, and malemale competition in primates. Hum. Nat. 23, 45–67. doi: 10.1007/ s12110-012-9130-3 Plyusnina, I., Oskina, I., and Trut, L. (1991). An analysis of fear and aggression during early development of behavior in silver foxes (Vulpes vulpes). Appl. Anim. Behav. Sci. 32, 253–268. doi: 10.1016/S0168-1591(05)80048-6 Progovac, L. (2015). Evolutionary syntax. Oxford studies in the evolution of language. Oxford: Oxford University Press. Progovac, L. (2016). A gradualist scenario for language evolution: precise linguistic reconstruction of early human (and Neandertal) grammars. Front. Psychol. 7:1714. doi: 10.3389/fpsyg.2016.01714 Progovac, L. (2019). A critical introduction to language evolution: Current controversies and future prospects. Springer briefs in linguistics: Expert briefs. (Cham, Switzerland: Springer). Progovac, L., and Locke, J. L. (2009). The urge to merge: ritual insult and the evolution of syntax. Biolinguistics 3, 337–354. Progovac, L., Rakhlin, N., Angell, W., Liddane, R., Tang, L., and Ofen, N. (2018a). Diversity of grammars and their diverging evolutionary and processing paths: evidence from functional MRI study of Serbian. Front. Psychol. 9:278. doi: 10.3389/fpsyg.2018.00278 Progovac, L., Rakhlin, N., Angell, W., Liddane, R., Tang, L., and Ofen, N. (2018b). Neural correlates of syntax and proto-syntax: an fMRI study. Front. Psychol. 9:2415. doi: 10.3389/fpsyg.2018.02415 Quist, M. C., Watkins, C. D., Smith, F. G., Little, A. C., Debruine, L. M., and Jones, B. C. (2012). Sociosexuality predicts women’s preferences for symmetry in men’s faces. Arch. Sex. Behav. 41, 1415–1421. doi: 10.1007/s10508-011-9848-8 Rakhlin, N., and Progovac, L. (2017). “Acquisition of clausal structure: the ‘weakest continuity’ view” in Proceedings of the 19th annual international conference of the Japanese Society for Language Sciences (JSLS), (Kyoto, Japan: Kyoto Women’s University), 54–57. Ridley, M. (1993). Evolution. Oxford: Blackwell Scientific Publications. Rilling, J. K., Scholz, J., Preuss, T. M., Glasser, M. F., Errangi, B. K., and Behrens, T. E. (2012). Differences between chimpanzees and bonobos in neural systems supporting socialcognition. Soc. Cogn. Affect. Neurosci. 7, 369–379. doi: 10.1093/scan/nsr017 Robinson, B. W. (1967). Vocalization evoked from forebrain in Macaca mulatta. Physiol. Behav. 2, 345–354. doi: 10.1016/0031-9384(67)90050-9 Rodriguiz, R. M., Chu, R., Caron, M. G., and Wetsel, W. C. (2004). Aberrant responses in social interaction of dopamine transporter knockout mice. Behav. Brain Res. 148, 185–198. doi: 10.1016/S0166-4328(03)00187-6 Rolls, E. T. (2015). Limbic systems for emotion and for memory, but no single limbic system. Cortex 62, 119–157. doi: 10.1016/j.cortex.2013.12.005 Roth, G., and Strüber, D. (2009). Neurobiological aspects of reactive and proactive violence in antisocial personality disorder and “psychopathy”. Prax. Kinderpsychol. Kinderpsychiatr. 58, 587–609. doi: 10.13109/ prkk.2009.58.8.587 Ruch, W., and Ekman, P. (2001). “The expressive pattern of laughter” in Emotion, qualia and consciousness. ed. A. Kaszniak (Tokyo: World Scientific), 426–443. Samarin, W. J. (1969). The art of Gbeya insults. Int. J. Am. Linguist. 35, 323–329. doi: 10.1086/465077 Sánchez-Villagra, M. R., and van Schaik, S. P. (2019). Evaluating the selfdomestication hypothesis of human evolution. Evol. Anthropol. 28, 1–11. doi: 10.1002/evan.21777 Sandler, W., Meir, I., Padden, C., and Aronoff, M. (2005). The emergence of grammar: systematic structure in a new language. Proc. Natl. Acad. Sci. U. S. A. 102, 2661–2665. Shea, B. (1989). Heterochrony in human evolution: the case for neoteny reconsidered. Am. J. Phys. Anthropol. 32:69e101. Singer, C. (1997). Tourette syndrome: coprolalia and other coprophenomena. Neurol. Clin. 15, 299–308. doi: 10.1016/S0733-8619(05)70314-5 Singer, H. S. (2005). Tourette’s syndrome: from behavior to biology. Lancet Neurol. 4, 149–159. doi: 10.1016/S1474-4422(05)70018-1 Singer, H. S., and Minzer, K. (2005). “Neurobiological issues in Tourette’s syndrome” in Handbook of Tourette’s and related tic and behavioral disorders. 2nd Edn. ed. R. Kurlan (New York: Marcel Dekker), 273–317. Progovac and Benítez-Burraco Language Evolution and Self-Domestication Feedback Loop Frontiers in Psychology | www.frontiersin.org 19 December 2019 | Volume 10 | Article 2807 Somel, M., Franz, H., Yan, Z., Lorenc, A., Guo, S., Giger, T., et al. (2009). Transcriptional neoteny in the human brain. Proc. Natl. Acad. Sci. USA 106, 5743–5748. doi: 10.1073/pnas.0900544106 Speedie, L. J., Wertman, E., T’air, J., and Heilman, K. M. (1993). Disruption of automatic speech following a right basal ganglia lesion. Neurology 43, 1768–1774. doi: 10.1212/WNL.43.9.1768 Stanyon, R., and Bigoni, F. (2014). Sexual selection and the evolution of behavior, morphology, neuroanatomy and genes in humans and other primates. Neurosci. Biobehav. Rev. 46, 579–590. doi: 10.1016/j.neubiorev.2014.10.001 Stillman, A. A., Krsnik, Z., Sun, J., Rasin, M. R., State, M. W., Sestan, N., et al. (2009). Developmentally regulated and evolutionarily conserved expression of SLITRK1 in brain circuits implicated in Tourette syndrome. J. Comp. Neurol. 513, 21–37. doi: 10.1002/cne.21919 Stowell, T. (1981). Origins of phrase structure. PhD dissertation. Cambridge (MA): Massachusetts Institute of Technology. Stringer, C. (2007). “The origin and dispersal of Homo sapiens: our current state of knowledge” in Rethinking the human revolution: New behavioral and bological perspectives on the origin and dispersal of modern humans. eds. P. Mellars, K. Boyle, O. Bar-Yosef, and C. Stringer (Cambridge, UK: McDonald Institute for Archeological Research, University of Cambridge), 15–20. Stringer, C. (2016). The origin and evolution of Homo sapiens. Philos. Trans. R. Soc. B Biol. Sci. 371:20150237. doi: 10.1098/rstb.2015.0237 Tallerman, M. (2013). “Kin selection, pedagogy, and linguistic complexity: whence protolanguage?” in The evolutionary emergence of language. eds. R. Botha and M. Everaert (Oxford: Oxford University Press), 77–96. Tamariz, M., and Kirby, S. (2016). The cultural evolution of language. Curr. Opin. Psychol. 8, 37–43. doi: 10.1016/j.copsyc.2015.09.003 Theofanopoulou, C. (2016). Implications of oxytocin in human linguistic cognition: from genome to phenome. Front. Neurosci. 10:271. doi: 10.3389/ fnins.2016.00271 Theofanopoulou, C., Boeckx, C., and Jarvis, E. D. (2017a). A hypothesis on a role of oxytocin in the social mechanisms of speech and vocal learning. Proc. Biol. Sci. 284:20170988. doi: 10.1098/rspb.2017.0988 Theofanopoulou, C., Gastaldon, S., O'Rourke, T., Samuels, B. D., Martins, P. T., Delogu, F., et al. (2017b). Self-domestication in Homo sapiens: insights from comparative genomics. PLoS One 12:e0185306. doi: 10.1371/journal. pone.0185306 Thomas, J., and Kirby, S. (2018). Self domestication and the evolution of language. Biol. Philos. 33:9. doi: 10.1007/s10539-018-9612-8 Thompson, B., Kirby, S., and Smith, K. (2016). Culture shapes the evolution of cognition. PNAS 113, 4530–4535. doi: 10.1073/pnas.1523631113 Trivers, R. L. (1972). “Parental investment and sexual selection” in Sexual selection and the descent of man, 1871–1971. ed. B. M. Campbell (Chicago: Aldine), 136–179. Trut, L., Oskina, I., and Kharlamova, A. (2009). Animal evolution during domestication: the domesticated fox as a model. BioEssays 31, 349–360. doi: 10.1002/bies.200800070 Ullman, M. T. (2006). Is Broca’s area part of a basal ganglia thalamocortical circuit? Cortex 42, 480–485. doi: 10.1016/S0010-9452(08)70382-4 Van Lancker, D., and Cummings, J. L. (1999). Expletives: neurolinguistic and neurobehavioral perspectives on swearing. Brain Res. Rev. 31, 83–104. doi: 10.1016/S0165-0173(99)00060-0 Viñas-Guasch, N., and Wu, Y. J. (2017). The role of the putamen in language: a meta-analytic connectivity modeling study. Brain Struct. Funct. 222, 3991–4004. doi: 10.1007/s00429-017-1450-y Vrticka, P., Black, J. M., and Reiss, A. L. (2013). The neural basis of humor processing. Nat. Rev. Neurosci. 14, 860–868. doi: 10.1038/nrn3566 Weekley, E. (1916). Surnames. New York: E.P. Dutton and Co. Whiting, B. B., and Edwards, C. P. (1973). A cross-cultural analysis of sex differences in the behavior of children aged three through eleven. J. Soc. Psychol. 91, 171–188. Wilkins, A. S., Wrangham, R. W., and Fitch, W. T. (2014). The “domestication syndrome” in mammals: a unified explanation based on neural crest cell behavior and genetics. Genetics 197, 795–808. doi: 10.1534/genetics.114.165423 Wong, K. (2017). Ancient fossils from morocco mess up modern human origins. Scientific American. Available at: https://www.scientificamerican.com/article/ ancient-fossils-from-morocco-mess-up-modern-human-origins/ (Accessed June 8, 2017). Wood, R. M., Rilling, J. K., Sanfey, A. G., Bhagwagar, Z., and Rogers, R. D. (2006). Effects of tryptophan depletion on the performance of an iterated Prisoner’s dilemma game in healthy adults. Neuropsychopharmacology 31, 1075–1084. doi: 10.1038/sj.npp.1300932 Woods, D. W., Piacentini, J., Himle, M. B., and Chang, S. (2005). Premonitory urge for tics scale (PUTS): initial psychometric results and examination of the premonitory urge phenomenon in youths with tic disorders. J. Dev. Behav. Pediatr. 26, 397–403. doi: 10.1097/00004703-200512000-00001 Wrangham, R. W. (2018). Two types of aggression in human evolution. PNAS 115, 245–253. doi: 10.1073/pnas.1713611115 Wrangham, R. W., and Glowacki, L. (2012). Intergroup aggression in chimpanzees and war in nomadic hunter-gatherers. Hum. Nat. 23, 5–29. doi: 10.1007/ s12110-012-9132-1 Wyatt, T. A. (1995). Language development in African American English child speech. Linguist. Educ. 7, 7–22. doi: 10.1016/0898-5898(95)90017-9 Wyatt, T. A. (1999). “An afro-centered view of communicative competence” in Constructing incompetence: Disabling evaluations in clinical and social interaction. eds. D. Kovarsky, J. F. Duchan, and M. Maxwell (Mahwah, NJ: Erlbaum), 197–223. Wynn, T., and Coolidge, F. L. (2004). The expert Neandertal mind. J. Hum. Evol. 46, 467–487. doi: 10.1016/j.jhevol.2004.01.005 Yang, Y., Joshi, S. H., Jahanshad, N., Thompson, P. M., and Baker, L. A. (2017). Neural correlates of proactive and reactive aggression in adolescent twins. Aggress. Behav. 43, 230–240. doi: 10.1002/ab.21683 Yang, Y., Raine, A., Colletti, P., Toga, A. W., and Narr, K. L. (2009). Abnormal temporal and prefrontal cortical gray matter thinning in psychopaths. Mol. Psychiatry 14, 561–562. doi: 10.1038/mp.2009.12 Zeng, T. C., Aw, A. J., and Feldman, M. W. (2018). Cultural hitchhiking and competition between patrilineal kin groups explain the post-Neolithic Y-chromosome bottleneck. Nat. Commun. 9:2077. doi: 10.1038/s41467-018-04375-6 Zheng, M., and Goldin-Meadow, S. (2002). Thought before language: how deaf and hearing children express motion events across cultures. Cognition 85, 145–175. doi: 10.1016/S0010-0277(02)00105-1 Zilhão, J. (2011). “Aliens from outer time? Why the ‘human revolution’ is wrong, and where do we go from here?” in Continuity and discontinuity in the peopling of Europe. One hundred fifty years of Neanderthal study. eds. S. Condemi and G.-C. Weniger (New York: Springer), 331–366. Zipser, B., Schleking, A., Kaiser, S., and Sachser, N. (2014). Effects of domestication on biobehavioural profiles: a comparison of domestic Guinea pigs and wild cavies from early to late adolescence. Front. Zool. 11:30. doi: 10.1186/ 1742-9994-11-30 Zollikofer, C. P. E., and Ponce de León, M. S. (2010). The evolution of hominin ontogenies. Semin. Cell Dev. Biol. 21, 441–452. doi: 10.1016/j.semcdb. 2009.10.012 Conflict of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could beconstrued as a potential conflict of interest. Copyright © 2019 Progovac and Benítez-Burraco. 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