This is the first volume to address directly the question of the speciation of modern Homo sapiens. The subject raises profound questions about the nature of the species, our defining characteristic, and the brain changes and their genetic basis that make us distinct. The British Academy and the Academy of Medical Sciences have brought together experts from palaeontology, archaeology, linguistics, psychology, genetics and evolutionary theory to present evidence and theories at the cutting edge of our understanding of these issues.Palaeontological and (...) genetic work suggests that the transition from a precursor hominid species to modern man took place between 100,000 and 150,000 years ago. Some contributors discuss what is most characteristic of the species, focussing on language and its possible basis in brain lateralization. This work is placed in the context of speciation theory, which has remained a subject of considerable debate since the evolutionary synthesis of Mendelian genetics and Darwinian theory. The timing of specific transitions in hominid evolution is discussed, as also is the question of the neural basis of language. Other contributors address the possible genetic nature of the transition, with reference to changes on the X and Y chromosomes that may account for sex differences in lateralization and verbal ability. These differences are discussed in terms of the theory of sexual selection, and with reference to the mechanisms of speciation.These essays will be vital reading for anyone interested in the nature and origins of the species, and specifically human abilities. (shrink)

Male superiority in mathematical ability (along with female superiority in verbal fluency) may reflect the operation of an X-Y homologous gene (the right-shift-factor) influencing the relative rates of development of the cerebral hemispheres. Alleles at the locus on the Y chromosome will be selected at a later mean age than alleles on the X, and only by females.

I agree with Burns that an evolutionary theory is required, but I question his multifactorial premise. The arguments for an evolutionary theory are stronger, and one that is more precise than that presented by Burns has already been formulated. This theory, that schizophrenia is “the price that Homo sapiens pays for language,” (Crow 1997a; 2000b, 2004c), generates testable predictions absent from Burns' presentation.

In 1873, within two years of the publication of The Descent of Man, Friedrich Max Mueller wrote: There is one difficulty which Mr Darwin has not sufficiently appreciated … There is between the whole animal kingdom on the one side, and man, even in his lowest state, on the other, a barrier which no animal has ever crossed, and that barrier is – Language … If anything has a right to the name of specific difference, it is language, as we (...) find it in man, and in man only … If we removed the name of specific difference from our philosophic dictionaries, I should still hold that nothing deserves the name of man except what is able to speak … a speaking elephant or an elephantine speaker could never be called an elephant.' and ‘If a pig were ever to say to me, “I am a pig” it would ipso facto cease to be a pig’. (shrink)

The claim of consistent hemispheric specialisations across classes of chordates is undermined by the absence of population-based directional asymmetry of paw/hand use in rodents and primates. No homologue of the cerebral torque from right frontal to left occipital has been established in a nonhuman species. The null hypothesis that the torque is the sapiens-specific neural basis of language has not been disproved.