The genetics and evolution of handedness.
At some point in hominid evolution, a mutation may have produced a "dextral" (D) allele, strongly biasing handedness in favor of the right hand and control of speech toward the left cerebral hemisphere. An alternative (chance [C]) allele is presumed directionally neutral, although there are probably other genes that influence asymmetries and that may create a weak bias toward right-handedness (and other asymmetries). Simulations show that the D allele could have spread quite quickly through a population, given even a minuscule advantage of CD heterozygotes over CC and DD homozygotes in terms of reproductive fitness. This heterozygotic advantage would also explain the apparent stability in the relative proportions of left-handers and right-handers. This putative, uniquely human allele may have emerged with the evolution of Homo sapiens in Africa some 150,000 to 200,000 years ago.
Corballis
M C
MC
Department of Psychology, University of Auckland, New Zealand. m.corballis@auckland.ac.nz
D000220:Adaptation, Biological; D000483:Alleles; D000818:Animals; D005075:Biological Evolution; D005260:Female; D007839:Functional Laterality / Q000235:genetics*; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D008297:Male; D008957:Models, Genetic