Over the years I have published a number of blog posts questioning the notion that the human capacity for language developed through a gradual, random process, that is to say, through a process of Darwinian evolution (for examples, see here and here). Recently, I discovered yet another piece of evidence calling into question the idea that human language evolved in a Darwinian sense.
This piece of evidence relates to the linguistic abilities of children. We often take it for granted that children are able to learn how to use language, but if we think more carefully about the development of language skills in children, the process is quite amazing. Within a few years of birth, a child is able to go from simple babbling to a rather sophisticated command of vocabulary and grammar. Moreover, according to research in the field of second language acquisition (the study of how individuals learn a language other than their native language), only children seem to be capable of learning to speak another language without a "foreign" (i.e., non-native) accent. Adults do not generally seem capable of doing this. In fact, in learning a second language children tend to perform better than adults not only in pronunciation but also in such areas as "accent recognition, listening comprehension and syntax [the structure of language]" (Diane Larsen-Freeman and Michael H. Long, An Introduction to Second Language Acquisition Research, p. 166).
In addition, children not only seem to have an advantage over adults in learning a second language, but also in recovering the ability to use language when areas in the left hemisphere of the brain associated with language processing have been damaged or destroyed. As Michael Denton points out, "Children can recover language ability even after these regions are lost. Amazingly, children who have lost their entire left hemisphere (which contains the key regions for language processing in normal adults) are still able to acquire and learn language." This is surprising if we assume that "the basis of language [lies] in genetically determined complex neural networks in the left side of the brain" (Denton). If this is true, according to Denton, "one might expect that damage to the areas in the left hemisphere known to be involved in language processing, i.e., Wernicke's and Broca's areas, would lead to linguistic impairment," which is true in adults--but, obviously, not in children.
This ability of children who have suffered brain damage to "reconstitute the language organ in a different part of the brain" (Denton) has an important implication for the Darwinian explanation for human language. Given that in the earliest stages of human life the language processing function does not need to be localized in particular regions of the brain, it seems unlikely that human linguistic competence "arose from a prolonged evolutionary process, directed by cumulative selection, which gradually reconfigured a vast suite of genetic changes in the genome and a corresponding set of neuronal changes in the brain" (Denton).
For his part, Denton argues that human language is an example of a saltation, that is, a sudden leap in the evolutionary process, rather than a capacity that evolved slowly over time. However, there are some problems with the idea of a saltation, not least the improbability that the multiple genetic changes required could have occurred within a short time span (a point made by Michael Behe in his Darwin Devolves and by other Intelligent Design theorists). Instead, I would argue that the human capacity for language was "built in" from the beginning by the Creator. Nevertheless, regardless of whether Denton's or my own view is correct, the ability of brain-damaged children to recover the use of language is yet another clear piece of evidence that the Darwinian explanation for the emergence of language is highly unlikely. [Note: this is a substantially rewritten version of an earlier blogpost that I felt lacked clarity.]
Diagram of major parts of the brain from Wikimedia Commons