Language Evolution and Computation Bibliography

This article explores the connection of the molecular evidence of evolutionary relationships between the various hominins with fossil evidence from the Plio- Pleistocene times, a period covering episodes of immense swings in temperature and rainfall, beginning about 5.5 million years ago (mya) and ending only about 11 kya. New technologies, allowing analysis of trace amounts of genetic material from human fossils, may help determine these relationships such as mitochondrial DNA indicates that widely-dispersed human groups apparently split into at least two descendant populations in the late Middle Pleistocene, perhaps during the period of global climate extremes 480-425 kya. The principle of a molecular clock underlies the use of DNA sequences or their derivatives as cellular fossils to aid reconstruction of speciation events. The estimation of mutation rates for nuclear (chromosomal) DNA is difficult because chromosomes, and the DNA which composes them, recombine and homogenize DNA sequences in every new generation, in addition to undergoing single base substitutions. The overall mutation rate for mitochondrial genes is about 2% every million years. Molecular dates using nuclear gene data support an early Miocene divergence for Asian and African apes at 18 mya, but mitochondrial timescales are younger, by 45 million years. It appears that the African great apes are the closest genetic relatives of humans, with estimated splits based on fossils between Homo and Pan dating from 67.5 mya.

This article concentrates on the three genes of recent interest in the literature on language origins. These genes are microcephalin and ASPM, which cause microcephaly when disabled and FOXP2, which causes a severe speech and language disability when disrupted. The FOXP2 gene was isolated, sequenced, classified as a member of the forkhead box family, and named FOXP2 by the year 2001. The protein products of forkhead genes have forkhead DNA binding domains, which bind to specified regulatory sequences in other genes, and regulate the expression of these other genes. FOXP2 is expressed in the mouse brain during development, but is also expressed in a wide variety of mouse tissues. The gene has many essential roles in mammalian development and function that are totally unrelated to language. It was announced in the year 2005 that two genes essential for proper brain growth, microcephalin and ASPM, are undergoing a change. Microcephalin and ASPM proteins are crucial for proper brain development. Microcephalin is involved in regulating the cell cycle especially in relation to DNA repair before cell division. ASPM helps to align the mitotic spindles in the cell so that it divides symmetrically. The defective versions of microcephalin and ASPM result in microcephaly, a genetic disorder in which people have small heads and small brains.

Language is a defining characteristic of the biological species Homo sapiens. But Chomskian Universal Grammar is not what is innate about language; Universal Grammar requires magical thinking about genes and genetics. Constraints of universal grammar are better explained in an evolutionary context by processes inherent in symbols, and by such processes as syntactic carpentry, metaphor, and grammaticalization. We present an evolutionary timeline for language, with biological evidence for the long-term evolution of the human capacity for language, and for the co-evolution of language and the brain.