Genetics and the Environment - Evidence That Genes Control Speechand Language

Although other species communicate with one another, speech is unique to humans, prompting scientists to question whether the ability to speak is determined genetically. In 1871 Darwin suggested that speech might be inherited when he observed that "man has an instinctive tendency to speak, as we see in the babble of our young children while no child has an instinctive tendency to bake, brew, or write" (Descent of Man, London: John Murray). In the twentieth century noted linguist Noam Chomsky (1928–) and neurologist Eric Lenneberg (1921–75) argued that specific characteristics of language—the fact that it is universal, complex, and rapidly acquired by children without explicit instruction—indicates that it is genetically determined. Research reporting that language impairments run in families, with higher concordance among identical than fraternal twins, supports the heritability of this trait.

In "A Forkhead-Domain Gene Is Mutated in a Severe Speech and Language Disorder" (Nature, vol. 413, no. 6,855, October 4, 2001), Cecelia Lai et al. announced research findings that offer substantive evidence of the involvement of a transcription factor for a specific gene, FOXP2, in the developmental process that culminates in speech and language. Lai and the other researchers hypothesized that FOXP2 has a causal role in the development of the normal brain circuitry that underlies language and speech, rather than simply functioning to disrupt that underlying circuitry when it is mutated. They also show that the FOXP2 gene is directly disrupted by a translocation in a patient with a speech and language disorder, and they concluded that future research will very likely reveal other genes, such as those regulated by FOXP2, that affect specific components of expressive language development.