Language and Life The Role of Development in Evolution Features
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Features  |   August 01, 2005
Language and Life
Author Notes
  • John L. Locke, is a professor in the Department of Speech-Language-Hearing Sciences at Lehman College, and the Doctoral Program in Speech and Hearing Sciences at the City University of New York. He also directs the Interdisciplinary Program in Linguistics at Lehman. Contact him at john.locke@lehman.cuny.edu.
    John L. Locke, is a professor in the Department of Speech-Language-Hearing Sciences at Lehman College, and the Doctoral Program in Speech and Hearing Sciences at the City University of New York. He also directs the Interdisciplinary Program in Linguistics at Lehman. Contact him at john.locke@lehman.cuny.edu.×
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Development / Special Populations / Genetic & Congenital Disorders / Speech, Voice & Prosody / Features
Features   |   August 01, 2005
Language and Life
The ASHA Leader, August 2005, Vol. 10, 6-26. doi:10.1044/leader.FTR2.10102005.6
The ASHA Leader, August 2005, Vol. 10, 6-26. doi:10.1044/leader.FTR2.10102005.6
Some years ago, I found that it was becoming impossible to think about the development of language-something that I had spent several decades doing-without also contemplating the way our species happened to come by the “parts” of the brain, body, and mind that do the developing.
Of course, the infants themselves are innocent in this matter. No one can drum up the hardware needed to learn and use a language. This machinery has to be “in there” already, at least in nascent form, as a legacy of prior generations. Even if development of the necessary systems requires environmental collaboration, much of the credit for language is attributable to the relevant genes, hence their origin: the evolutionary events that produced them.
The genes responsible for language are powerful, so potent that parents desirous of linguistic offspring need do little more than converse within earshot of their hearing children. As fledgling members of a gregarious species, infants naturally pay attention to people, who spend much of their time talking. With other cognitive systems in place, the mechanisms that “do” language, at least when mature and “ready,” spring to life. After surprisingly few fits and starts, infants speak.
Note that the flow in this scenario begins with evolution, which seeds the human fetus with genes that build the kind of brain tissue that language mechanisms are made of. Then, maturation and experience prepare the mechanisms, and give them specific content to learn and manipulate. The infant in this pageant is both an inheritor and an actor, but without the proper inheritance there will be little to do-little, at least, that is linguistic.
Rethinking Evolution
All this seems to be true, more or less, but there is a rather different way of thinking about the sequence of action and inheritance in evolution, which I discuss in several recent papers. For when one seriously asks my original question-where did the language genes come from?-it appears that the sequence is now reversed: development precedes evolution.
It is not as though evolutionary biologists always knew this. Most, including Darwin himself, thought that the individuals to whom his theory of natural selection applied were fully-formed adults. If infants or any other sub-adults were involved, it was by being on the receiving end.
At first glance, this seems to make sense. How, after all, could infants-as individuals who are literally in fans, “not speaking”-contribute much of anything to the evolution of language? In the harsh conditions of premodern life, it was all they could do to survive. But some biologists began to raise a rather different question. How, they asked, could evolution occur if the young were not involved?
To become an adult, as anthropologist Barry Bogin has written in The Growth of Humanity, individuals have to pass through all the preceding life history stages, with layovers in infancy, childhood, juvenility, and adolescence before the final transition into maturity. It is during these pre-adult stages that adults are formed. Since Walter Garstang’s influential article in 1922, biologists have come to accept that if nothing different ever happens in one or more of these earlier stages, the adults will remain the same from one generation to the next. Gilbert Gottlieb has vividly recounted the relevant scientific history in his interesting book, Individual Development and Evolution.
Gottlieb also described the emergence of a rather different conception, one pertaining to the role of individuals’ own behavior. It has long been known that evolution is the likely result when individuals adapt to altered conditions. But “environmental changes” conjures up images of catastrophic floods, droughts, and glaciers that happen along to disrupt otherwise stable living conditions.
In fact, environmental challenges also vary when individuals move around. Historically, our ancestors provided themselves with a range of different environmental pressures as a result of their own actions. This tendency clearly identifies behavior as a major agent in evolutionary change, just as the earlier discovery called attention to the role of development. The conjunction of these perspectives made me think about whatever role in linguistic evolution might have been played by the behavior of the young.
In my own research, much of it inspired by the work of Kim Oller and Michael Studdert-Kennedy, the goal has been to explain the vocal and articulatory behaviors that launched and currently support linguistic phonologies. These behaviors appear to have evolved as precursive steps in the construction of language, it making less sense that the capacity for syntax-the focus of many proposals-evolved prior to the physical system responsible for the phonetic units that made words and massive vocabularies possible.
It is best to keep in mind, in this connection, that all six to eight thousand languages in the (hearing) world are spoken-not some compelling percentage, but all of them. This vocal exclusivity requires an explanation, especially in the face of evidence that signed and spoken languages are learned at similar rates. Indeed, it is possible that when we are able to account for speech, the universal modality of language, we will take a huge step closer to an explanation of language itself.
I have a few possibilities to suggest as to how sub-adults may have contributed to the evolution of language. It is now understood that at some point after our ancient ancestors, the hominids, abandoned arboreal life, they began to spend more time walking on their hind legs. Reliance on this new bipedal means of locomotion eventually realigned the spine and narrowed the female birth canal. At birth, the hominid fetus-whose head was already larger than that of other primate newborns-was barely able to pass through the canal. This “obstetrical dilemma,” as one biologist called it, imperiled the life of mother and child.
There being a range of variation among infants, some had smaller heads at birth. They and their mothers were more likely to survive the delivery. Over time, differential rates of survival caused a shift in skull and brain development from the prenatal to the postnatal period, when the infant was safely on the outside and the brain was free to resume its rapid rate of growth. This solved one problem, but it produced a new one-perhaps the best “problem” that our species ever faced. For bipedalism made newborn infants more helpless than ever.
If it seems preposterous that helplessness could ever be good, ask yourself this: how beneficial would it be for any kind of social or cultural learning-including whatever kinds go into language-if newborns wandered away from their parents at birth, never to return?
Because the large-brained hominid infants, like our own, were motorically immature, they could do little to decrease maternal proximity. They also had to be cared for more intensively than ancestral infants, and for a longer period. This constant contact with the mother and other caregivers produced significant new levels of interaction.
But more intensive care was not guaranteed. As infants developed, they could no longer count on parental attention-increasingly this had to be demanded-and herein lay a problem. If infants demanded too little, they were in danger of getting insufficient care. If they demanded too much attention, or did so noxiously, they were in danger of abandonment or homicide.
Uses of the Voice
It helps to consider the proposal of biologist Robert Trivers that the birth of an infant sets up an instant “parent-offspring conflict.” When the mother begins to withdraw her attention, as eventually she must, the infant begins to “negotiate” continued care. This put a new emphasis on strategic signaling, particularly on clever new ways of using the voice to secure and maintain maternal proximity, with an additional premium on the ability to monitor and “read” maternal feedback. The infants who were able to deal with these new signaling situations were more likely to receive the care they needed.
Some of these clever ways of vocalizing were undoubtedly bogus-infant monkeys may not be incapable of “crying wolf,” as my colleague Marc Hauser has implied-and hominid mothers undoubtedly experienced new pressures to distinguish sincere bids for attention from false ones. They also had to provide increased levels of care merely to keep their infants alive. Thus, a change in behavior-bipedalism-caused a series of shifts that altered human development, with effects on infants’ sound-making activities, the maternal perceptual system used to detect changes in their vocal activity, and the amount of interaction between caregivers and their young. What better context for the evolution of new ways to make sounds, and to use any new and more complex sounds attractively and persuasively?
According to my “parental selection” hypothesis, infants whose sound making seemed normal were given the care they needed, and infants whose vocal and phonetic behavior were precocious were given levels of attention-and social engagement-that were generous. When crying was perceptibly healthy, and cooing and babbling were indicative of typical development, overly burdened caregivers were able to justify-yes, “justify” in a time when infanticide was the preferred method of family planning-continued investment of time, food, and other precious resources.
An implication of development-as-causation relates to the effects of infant behaviors-now understood to be highly creative, especially where language is concerned-on the behavior of their less inventive caregivers. Although one is used to thinking that the young get inspiration for their behaviors from adults, it is frequently the other way around. Several studies of vocal imitation have shown that in the first year of life, it is typically the mother who does the imitating. Many of the words we use with infants-mama, dada, wawa-are “baby words” that originated with babies and were then taken up by their observant parents. Elsewhere, I have called this “trickle up phonetics,” but it could also be called “trickle up vocabulary.”
There is much more to be said about the role of developmental stages in the evolution of language, in which new pressures emerge in connection with competition and courtship. I am currently investigating the role of all these stages in collaboration with Barry Bogin.
When the contributions of life history to human evolution are fully understood, it will be natural for everyone who contemplates the development of language, or its evolution, to think about the relationship between the two. The benefits of doing so are suggested by the name of an emerging field of study: “evolutionary developmental biology.”
References
Bogin, B. (2001). The growth of humanity. New York: Wiley-Liss.
Bogin, B. (2001). The growth of humanity. New York: Wiley-Liss.×
Garstang, W. (1922). The theory of recapitulation: A critical re-statement of the biogenetic law. Journal of the Linnaean Society (Zoology), 35, 81–101.
Garstang, W. (1922). The theory of recapitulation: A critical re-statement of the biogenetic law. Journal of the Linnaean Society (Zoology), 35, 81–101.×
Gottlieb, G. (1992). Individual development and evolution: The genesis of novel behavior. Mahwah, NJ: Erlbaum.
Gottlieb, G. (1992). Individual development and evolution: The genesis of novel behavior. Mahwah, NJ: Erlbaum.×
Hauser, M. D. (1993). Do vervet monkey infants cry wolf? Animal Behaviour, 45, 1242–1244. [Article]
Hauser, M. D. (1993). Do vervet monkey infants cry wolf? Animal Behaviour, 45, 1242–1244. [Article] ×
Locke, J. L. (1985). The role of phonetic factors in parent reference. Journal of Child Language, 12, 215–220. [PubMed]
Locke, J. L. (1985). The role of phonetic factors in parent reference. Journal of Child Language, 12, 215–220. [PubMed]×
Locke, J. L. (1998). Social sound-making as a precursor to spoken language. In Hurford, J. R., Studdert-Kennedy, M., & Knight, C. (Eds.), Approaches to the evolution of language: Social and cognitive bases. Cambridge: Cambridge University Press, pp. 190–201.
Locke, J. L. (1998). Social sound-making as a precursor to spoken language. In Hurford, J. R., Studdert-Kennedy, M., & Knight, C. (Eds.), Approaches to the evolution of language: Social and cognitive bases. Cambridge: Cambridge University Press, pp. 190–201.×
Locke, J. L. (2000). Rank and relationships in the evolution of spoken language. Journal of the Royal Anthropological Institute, 7, 37–50.
Locke, J. L. (2000). Rank and relationships in the evolution of spoken language. Journal of the Royal Anthropological Institute, 7, 37–50.×
Locke, J. L. (2004). Trickle up phonetics: A vocal role for the infant. Behavioral and Brain Sciences, 27, 516.
Locke, J. L. (2004). Trickle up phonetics: A vocal role for the infant. Behavioral and Brain Sciences, 27, 516.×
Locke, J. L. (in press). Parental selection of vocal behavior: Crying, cooing, babbling, and the evolution of language. Human Nature.
Locke, J. L. (in press). Parental selection of vocal behavior: Crying, cooing, babbling, and the evolution of language. Human Nature.×
Locke, J. L., & Hauser, M. D. (1999). Sex and status effects on primate volubility: clues to the origin of vocal languages? Evolution and Human Behavior, 20, 151–158. [Article]
Locke, J. L., & Hauser, M. D. (1999). Sex and status effects on primate volubility: clues to the origin of vocal languages? Evolution and Human Behavior, 20, 151–158. [Article] ×
Oller, D. K. (2000). The emergence of the capacity for speech. Mahwah, NJ: Erlbaum.
Oller, D. K. (2000). The emergence of the capacity for speech. Mahwah, NJ: Erlbaum.×
Studdert-Kennedy, M. (1991). Language development from an evolutionary perspective. In Krasnegor, N. A., Rumbaugh, D. M., Schiefelbusch, R. L., & Studdert-Kennedy, M. (Eds.), Biological and behavioral determinants of language development. Hillsdale, NJ: Erlbaum, pp. 5–28.
Studdert-Kennedy, M. (1991). Language development from an evolutionary perspective. In Krasnegor, N. A., Rumbaugh, D. M., Schiefelbusch, R. L., & Studdert-Kennedy, M. (Eds.), Biological and behavioral determinants of language development. Hillsdale, NJ: Erlbaum, pp. 5–28.×
Studdert-Kennedy, M. (2005). How did language go discrete? In Tallerman, M. (Ed.), Language origins: perspectives on evolution. Oxford: Oxford University Press, pp. 48–67.
Studdert-Kennedy, M. (2005). How did language go discrete? In Tallerman, M. (Ed.), Language origins: perspectives on evolution. Oxford: Oxford University Press, pp. 48–67.×
Trivers, R. L. (1974). Parent-offspring conflict. American Zoologist, 14, 249–264.
Trivers, R. L. (1974). Parent-offspring conflict. American Zoologist, 14, 249–264.×
Selected Books on the Evolution of Language
Christiansen, M., & Kirby, S. (Eds.) (2003). Language evolution. Oxford: Oxford University Press.
Christiansen, M., & Kirby, S. (Eds.) (2003). Language evolution. Oxford: Oxford University Press.×
Hurford, J. R., Studdert-Kennedy, M., & Knight, C. (Eds.). (1998). Approaches to the evolution of language: Social and cognitive bases. Cambridge: Cambridge University Press
Hurford, J. R., Studdert-Kennedy, M., & Knight, C. (Eds.). (1998). Approaches to the evolution of language: Social and cognitive bases. Cambridge: Cambridge University Press×
Knight, C., Studdert-Kennedy, M., & Hurford, J. R. (Eds.). (2000). The evolutionary emergence of language: Social function and the origins of linguistic form. Cambridge: Cambridge University Press.
Knight, C., Studdert-Kennedy, M., & Hurford, J. R. (Eds.). (2000). The evolutionary emergence of language: Social function and the origins of linguistic form. Cambridge: Cambridge University Press.×
Oller, D. K., & Griebel, U. (Eds.). (2004). The evolution of communication systems: A comparative approach. Cambridge, MA: MIT Press.
Oller, D. K., & Griebel, U. (Eds.). (2004). The evolution of communication systems: A comparative approach. Cambridge, MA: MIT Press.×
Tallerman, M. (Ed.). (2005). Language origins: Perspectives on evolution. Oxford: Oxford University Press.
Tallerman, M. (Ed.). (2005). Language origins: Perspectives on evolution. Oxford: Oxford University Press.×
Wray, A. (Ed.). (2002). The transition to language. Oxford: Oxford University Press.
Wray, A. (Ed.). (2002). The transition to language. Oxford: Oxford University Press.×
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August 2005
Volume 10, Issue 10