Language and life history: A new perspective on the development ...

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Response/Locke & Bogin: <strong>Language</strong> <strong>and</strong> <strong>life</strong> <strong>history</strong>performances of 3- to 5-year-old African American boyswere captured on audiotape <strong>and</strong> transcribed. In one case,a spontaneous rap, a boy expressed his feelings towardone of the female research assistants on whom he haddeveloped a crush. In the other case, three boysengaged in “the dozens” (Wyatt 1995; 1999). These boyswere playing, but a decade later they would be expectedto enlist their verbal abilities as adaptive strategies, onesthat would help them to attract females, avoid violence,<strong>and</strong> compete for status with same-sex peers.To this point, we have exposed few connectionsbetween linguistic function <strong>and</strong> form, but if there was areproductive advantage of vocal <strong>and</strong> verbal complexity,runaway selection – which, as Harvey <strong>and</strong> Arnold (1982)point out, would certainly have applied to vocalization –may have produced a huge increase in the complexity ofspeech <strong>and</strong>, therefore, the possibility of complexity atother levels of language, <strong>and</strong> possibly in other modalities.If speech were kept simple, observers would have to findother ways to make the necessary inferences.If a performance is rhythmic or euphonious, <strong>and</strong> thematerial novel or complex, then it is possible that form<strong>and</strong> function interact. Are there relationships betweenthe quality of the dance <strong>and</strong> the ornamentation of thedancer? There are multiple cues to attractiveness inother species, <strong>and</strong> these interact in extremely complexways to produce their effect (Badyaev & Hill 2003;C<strong>and</strong>olin 2003; van Doorn & Weissing 2004). They evencomplement each other (Badyaev et al. 2002; Colemanet al. 2004; Johnson 1999). In our own species, too, speakersare evaluated along with their messages. It is possiblethat in display mode, the evaluations of others are basedboth on structural complexity <strong>and</strong> behavioral finesse.R6. Genetic support of verbal performanceWe have proposed that vocal <strong>and</strong> verbal skills enable adolescents<strong>and</strong> young adults to engage <strong>and</strong> compete withothers, <strong>and</strong> to perform in public arenas – the relevantabilities increasing their fitness. Now it could be saidthat these verbal dimorphisms were merely brought tothe surface <strong>and</strong> made observable by underlying sex differencesin the tendency to compete <strong>and</strong> aggress (Fitch 2005,p. 212). But, for behavioral traits, as opposed to physicalones that are readily perceptible, such as size, the individualmust be motivated to act in the first place, <strong>and</strong> thesource of the motivation may be an internal change. Infact, if anything was selected directly, it was vocal <strong>and</strong>verbal ability. The indirect effects were the supportingphysiological variables. Thus, males’ greater dispositionto compete – secondary to increases in testosterone –may have increased the functionality of their vocal <strong>and</strong>verbal ability while also making it public, raising the probabilitythat these skills would be selected, <strong>and</strong> tighteningthe links between speech <strong>and</strong> testosterone. If so, onemight expect a genetic legacy: genes that code specificallyfor verbal expressivity <strong>and</strong> dominance in modern humans.Recently we came across several reports indicating thatmonozygotic twins, but not dizygotic twins, are highly concordanton measures of social potency <strong>and</strong> expressivecontrol, tests that tap the ability to act or perform insocial situations, even where the twins have been rearedapart (Gangestad & Simpson 1993; Lykken 1982).Significantly, individuals who were unusually social <strong>and</strong>expressive reported that they had engaged in sex withmore partners, <strong>and</strong> with more partners on just oneoccasion, than their less social <strong>and</strong> expressive peers(Snyder 1987).With such high concordance rates, one might expect tosee differences in sociality <strong>and</strong> expressiveness appearingearly in <strong>life</strong> <strong>history</strong>. It is interesting, in this connection,that investigators in other fields have documented theexistence of unusually social <strong>and</strong> expressive individualsin infancy (cf. Nelson 1973; 1981), termed “dramatists”by Wolf <strong>and</strong> Gardner (1979) since they appear to learnat an early age that different individuals can exchangeroles in identical social situations. Dramatists also like totell dramatic stories <strong>and</strong> display elaborate forms of imitation.On the basis of content validity, Gangestad <strong>and</strong>Snyder (1986) speculated that such expressive differencesin infancy <strong>and</strong> adulthood are manifestations of the samelatent factor.This section on the genetics of verbal performance is aconvenient place to acknowledge the kind remarks ofWorkman, who does, however, misinterpret our discussionof FOXP2, thinking that we see in this gene a basisfor linguistic grammar. In fact, we referred to the behavioralresearch leading to the identification of this genebecause it related to the role in language that is playedby “production factors.” We pointed out that problemsexperienced by the KE family “included a severe oral<strong>and</strong> verbal dyspraxia, accompanied by deficits at otherlevels of language” (emphasis added), <strong>and</strong> quoted fromseveral theorists who suggest that speech might have acertain primacy that has been neglected in the past. Thissupported our argument that verbal performance wasselected.R7. Performance as adaptationWhat supported the use of vocal <strong>and</strong> speech-like activitybefore there was speech? Knight & Power doubt ouraccount of reproductive advantages because, they say, linguisticsigns represent no “cost” or investment. They fail torecognize several things. First, the resting metabolic rate(RMR) of the human brain exacts a continuously highenergetic cost from infancy, as mentioned in the targetarticle <strong>and</strong> in section R1. Were this not so, manycomplex human activities, including language, would beimpossible. Second, articulated phonation carries a greatdeal of information about the individual, whether or notit is consciously transmitted. Apes rely on this information<strong>and</strong> so do we. Third, potentially informative componentsof the voice are supported by physiological activity thatis energetically expensive (e.g., pulmonary pressure; cf.Fitch & Hauser 2002). Fourth, traits will be selected iffemales prefer them, <strong>and</strong> not everything females preferis costly (Johnson 1999). Finally, the mere uttering ofcertain words (or other constructions), especially rareones, may reflect a great deal of prior learning – learningthat presupposes the efficient action of relevant mechanisms.Merely to use a behavior that was learned, orrequires an unusual mode of articulation, can mean thatthe individual has an intact nervous system, has theability to attend, perceive, store, retrieve, <strong>and</strong> reproducecomplex patterns of behavior, <strong>and</strong> can do so meaningfully310 BEHAVIORAL AND BRAIN SCIENCES (2006) 29:3
Response/Locke & Bogin: <strong>Language</strong> <strong>and</strong> <strong>life</strong> <strong>history</strong>in an appropriate social context. The energetic requirementsof the motoric act, <strong>and</strong> the veracity of any statements,are not the only relevant factors.Dickins sees a need to identify proximate mechanismsfor the actions that we propose, <strong>and</strong> Powers would likeus to have made more explicit predictions. Perhaps weunderplayed our effort to construct an adaptive accountof vocalization in relation to social dominance <strong>and</strong> courtship.In section 8, we suggested that women who areattracted to men with a comm<strong>and</strong>ing way of speakingmay get a mate for themselves, <strong>and</strong> a father for their children,who has high levels of testosterone <strong>and</strong> status, <strong>and</strong>unusual access to valued resources. Specifically, we evaluatedresearch that reveals connections between propertiesof male voices, as measured acoustically <strong>and</strong> appraised perceptually,<strong>and</strong> both virility <strong>and</strong> social dominance. In light ofother research, we would predict that women prefer thevoices of men who are high in testosterone, especiallywhen heard during ovulation (Fisher 2004; Puts 2005).In the target article we reviewed research indicating thatthe speech of courting men contains unusually wide frequency<strong>and</strong> intensity swings, <strong>and</strong> that young women,when asked to evaluate utterances extracted from children’sconversations, expressed a preference for selections thatwere classified as excitable, loud, <strong>and</strong> uncontrolled,among related variables. Taken together, these behaviorscould suggest the operation of a sensory trap (after thepattern described in insects <strong>and</strong> other animals) in whichsexually mature males mimic the vocal qualities thatappear to excite females (Christy 1995; Enquist & Arak1993; Macias Garcia & Ramirez 2005). Surely there is rawmaterial here for testable hypotheses on the fitness benefitsnot just of speech, but of particular aspects of prosody, <strong>and</strong>investigations could easily be extended into lexical <strong>and</strong>other areas of spoken language. To implement such anagenda in the context of linguistic evolution, it will ofcourse be necessary to investigate the perceptual preferencesof sexually mature females <strong>and</strong> the use of male vocalization<strong>and</strong> speech in social competition <strong>and</strong> courtship, <strong>and</strong>this is exactly the kind of research that we propose. In li<strong>new</strong>ith a st<strong>and</strong>ard approach in biology, it would then be possibleto look at which vocal variables were most stronglylinked to perceptions <strong>and</strong> proximate variables that indexfitness. By carrying out a research agenda of this sort, onedoes not show how language evolved, of course, but onemay be able to argue for the plausibility of a particularproposal on the basis of empirical data.Dickins is not sure that we adequately supported ourclaim that the components of language are related, but itcan only be so if, as we argued in the target article <strong>and</strong>repeated earlier in this response (sect. R3), they werestitched together by sequential patterns of selection. Behaviorsthat were selected at sexual maturity, such as verbalpersuasiveness, could not have appeared without somelevel of pragmatic development, <strong>and</strong> without linguisticskills that rest on previous accomplishments in the areaof lexical, phonological, morphological, <strong>and</strong> syntacticdevelopment. We noted in this context, additionally, thewell-attested observation that development is continuous,behaviors not usually emerging de novo in later ontogeneticstages without an appearance, in some form, in oneor more of the preceding ones. We also cited evidencesuggesting that individuals having problems in one areaof language tend to have problems in other areas.Johansson et al. say that we failed to show “thatlanguage was useful <strong>and</strong> adaptive specifically for protohumans<strong>and</strong> not for proto-chimpanzees.” Ragir &Brooks seem to think, in parallel, that if language benefitshumans, it should have benefited the other primatesequally. If it did, they say, the behavior would have followed.But these comments miss the point. The questionis not who language could have assisted, but rather, inwhom it could have evolved. In section R1, we point outthat hominins took a different path, one that led to cooperativebreeding <strong>and</strong> protolanguage, <strong>and</strong> thereforeevolved a completely different <strong>life</strong> <strong>history</strong>.Ragir & Brooks comment that performance is beneficialat every stage of language development, not justin adolescence. That we also believe this is why wedevoted so much attention to proposals regarding infantbehavior, including parental selection <strong>and</strong> trickle-up phonetics.In the target article, we argued that skillful vocalperformances by adolescent <strong>and</strong> adult male homininswould have facilitated their quest for rank <strong>and</strong> reproduction.Ragir & Brooks express doubt about a portion ofthis argument since, they say, female apes fail to show apreference for alpha males. The relevance of this isunclear, since our claim is that there were changes inhominins that occurred following their divergence fromshared lineage. As indicated in the target article, wetrace these changes to pre-adult stages when controlover <strong>new</strong> <strong>and</strong> more variegated vocal behaviors emergedunder environmental pressures that remodeled humaninfancy <strong>and</strong> contributed to the evolution of childhood.R8. PluralismWe noted at the beginning of section R2 that in the first stageof evolution, environmental variation produces novel formsthat vary genetically, <strong>and</strong> that in the second stage of evolution,selection acts on the variants. According to ouraccount, infancy <strong>and</strong> childhood produced <strong>new</strong> abilities toeffect <strong>and</strong> manipulate vocal forms, with selection occurringin those stages <strong>and</strong> perhaps more powerfully at sexual maturity.To us, the development <strong>and</strong> evolution of language – <strong>and</strong>ultimately its nature – are interrelated. Work in one areapotentially affects progress in the other. Theorists mustintegrate findings in psychology, biology, animal behavior,anthropology, archaeology, genetics, <strong>and</strong> linguistics ifthese benefits are to be appreciated. In our own attemptto explain the evolution <strong>and</strong> modification of <strong>life</strong> <strong>history</strong>stages, we needed to integrate findings from archaeologywith findings on the development of brains, teeth, endocrinesystems, <strong>and</strong> other characteristics of modern humans. Wethink that such efforts will eventually produce a small steptoward the unification of a broad base of language-relevantknowledge, emanating from a wide range of disciplines.Theorists also need to explain developments across thevarious stages of linguistic evolution, not merely thosepertaining to language as it is, or as it appears, now. Wehave claimed that insertion of <strong>new</strong> ontogenetic stages intohuman <strong>life</strong> <strong>history</strong>, <strong>and</strong> the remodeling of others, produced<strong>new</strong> developmental processes that fashioned novelcommunicative behaviors <strong>and</strong> increased fitness. If so,reciprocal action by evolutionary <strong>and</strong> developmentalmechanisms – working in an “evo-devo-evo” sequence –may have played a major role in the evolution of language.BEHAVIORAL AND BRAIN SCIENCES (2006) 29:3 311
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