On Language: Descent From the Tower of Babel
Humans are the only species that has evolved an advanced system of communication between individuals. Whereas other species communicate through ritualized and repetitious songs, calls, or gestures, humans have developed linguistic systems that can express a literally infinite variety of separate and distinct thoughts. This incredible evolutionary leap is what distinguished humans from all other organisms on earth.
The Evolution of Language
Language first appeared between 30,000 and 100,000 years ago in the species Homo sapiens. But how did language evolve? Currently, there are two rival answers to this question: the first and more common explanation is that language was an adaptation of some sort; the second (chiefly espoused by Stephen Jay Gould) is that language is a spandrel, a nonadaptive element arising as a byproduct of other processes. We will consider these explanations in reverse order.
Language as a Spandrel
Some people, Stephen Jay Gould most prominent among them, believe language to be the byproduct of other evolutionary processes, not a special adaptation that arose by ordinary natural selection acting on mutations. As Gould puts it, "Natural selection made the human brain big, but most of our mental properties and potentials may be spandrels - that is, nonadaptive side consequences of building a device with such structural complexity" (The Pleasures of Pluralism , p.11). In other words, our ancestors encountered environments which required the type of advanced reasoning only provided by a larger brain; however, language capability was not one of those functions for which the brain was selected. Instead, language is a result of exapting neural structures formerly used for other functions: "Many, if not most, universal behaviors [including language] are probably spandrels, often co-opted later in human history for important secondary functions" (Ibid).
This view has been reinforced by the famous linguist Noam Chomsky, who argues that the brain's language capability cannot be explained in terms of natural selection. He attempts to explain the brain not through biology or engineering principles, but instead through the effects of physical laws. According to Chomsky, there may be unexpected emergent physical properties associated with the specific structure of the brain that explain language.
Language as an Adaptation
The mainstream view is that language is an adaptation, evolved in response to some selection pressure toward improved communication between humans. This explanation is associated with many speculative possibilities and proposals for the adaptive function of language, and some (such as Steven Pinker) postulate "mental modules" that compartmentalize linguistic functions.
There are many different possible "adaptationist" explanations for the evolution of language. For instance, perhaps there was a need for improved communication between hunters at some point in the history of Homo sapiens, and oral expressions were simply the optimal way to solve the problem. More plausibly (or at least more importantly), sharing information between individuals probably conferred an extremely major advantage: groups of humans with language, or even "proto-language", could share a wealth of information about local hunting conditions, food supplies, poisonous plants, or the weather. It would be extremely beneficial to the survival of all members of the tribe if only one had to encounter a poisonous plant, rather than each member having to rediscover the fact for himself!
It is also simple to imagine a series of "oral gestures", perhaps indicating the presence of an animal to another person by imitating the animal's cries. Steven Pinker suggests in his book The Language Instinct, "Perhaps a set of quasi-referential calls . . . came under the voluntary control of the cerebral cortex [which controls language], and came to be produced in combination for complicated events; the ability to analyze combinations of calls was then applied to the parts of each call" (p. 352).
Another possible source of selection pressure towards better linguistic abilities is the social group. Social interactions between people with widely divergent or conflicting interests "make formidable and ever-escalating demands on cognition" (Ibid, p.368). Increasing cognitive ability could easily have focused on the improvement of language as well, since so many social interactions depend on effective persuasion.
Language Evolution and Memes
It is possible to imagine numerous potential scenarios by which language might have evolved as a purely biological adaptation. However, in her book The Meme Machine, Susan Blackmore reveals a different theory of language evolution: she proposes that it evolved for the sake of memes, not as an adaptation for the benefit of genes.
Blackmore explains that memes first came into existence with the advent of true imitation in humans, which allowed memes to spread through populations. Recalling that fecundity, or proudction of new copies, is essential to a replicator, she proposes that language came into existence as a mechanism for improving the fecundity of memes. Sound transmission has many advantages for the purpose - sounds can be heard by multiple listeners and can be used even at night. After sound transmission (proto-language) came into existence, the "digitalization" of language into discrete words arose as a mechanism for ensuring meme fidelity, or lack of errors in the new copies. She explains that those alterations that produce the most copies of the highest fidelity will be those that predominate, thus improving the language.
Blackmore goes on to suggest that grammar was an adaptation to improve the fecundity and fidelity of existing memes; its recursive structure then provided the framework for the development of more complex memes, which then favored the existence of more complex grammar, etc. in a self-sustaining process. Furthermore, language then began to exert pressure on the genes, creating a selection pressure toward bigger brains that are better at language. If people prefer to mate with those possessing the best or most memes, then the genes that allowed those people to be good meme-spreaders will be differentially transmitted into the next generation. This process again leads to a self-catalytic process of brain evolution that places a strong survival and reproductive advantage on those most capable of meme transmission.
Finally, Blackmore believes that language is an unavoidable result of the existence of memes, which follow naturally from the ability to imitate (an ability that is, surprisingly, realized in very few species). She states, "verbal language is almost an inevitable result of memetic selection. First, sounds are a good candidate for high-fecundity transmission of behaviour. Second, words are an obvious way to digitise the the process and so increase its fidelity. Third, grammar is a next step for increasing fidelity and fecundity yet again, and all of these will aid memorability and hence longevity" (p.105).
Looking Further: Links and References
The following links and references are useful in the study of the evolution of language.
The Language Instinct by Steven Pinker
How the Mind Works by Steven Pinker
Words and Rules by Steven Pinker
The Meme Machine by Susan Blackmore
Darwin's Dangerous Idea: Evolution and the Meanings of Life by Daniel C. Dennett (see ch. 13)
Evolution: The Pleasures of Pluralism by Stephen Jay Gould (also available here)
'Darwinian Fundamentalism': An Exchange - discussion between Daniel C. Dennett, Robert Wright, and Stephen Jay Gould
Evolutionary Psychology: An Exchange - discussion between Stephen Jay Gould and Steven Pinker
The Gestural Origins of Language by Michael C. Corballis (from American Scientist)