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Abstract

5 to 6 million years ago, 3.5 megabase of DNA duplicated from the long arm of the X to create a Hominid-specific stratum on the Y short arm. Such events constitute �saltations� and this particular change is a candidate for the speciation event for Australopithecus. Within the transposed block a gene pair - Protocadherin X. and Protocadherin Y - has been subject to accelerated evolution, with 16 amino acid changes in the Y protein and five in the X. The latter are particularly significant in that they include the introduction of two sulphur containing cysteines, that are likely to have changed the function of the molecule, and are expressed in both males and females. The sequence changes are seen as secondary to chromosomal rearrangements on the Y. (four deletions and a paracentric inversion), the latter representing the initiating events in successive speciations, and the former representing the sexually selected phase of accommodation that establishes a new mate recognition system. The paracentric inversion, which has not been dated, is a candidate for the sapiens speciation event. Cerebral asymmetry (the torque), may have been introduced at a late stage, perhaps as recently as 160KYA.

@incollection{crow08evolang7th,
  author={Tim J. Crow},
  title={Language, the Torque and the Speciation Event},
  year={2008},
  month={March},
  pages={67-74},
  editor={A. D. M. Smith and K. Smith and R. Ferrer-i-Cancho},
  publisher={World Scientific},
  booktitle={Proceedings of the 7th International Conference on the Evolution of Language},
  url={http://www.isrl.uiuc.edu/~amag/langev/paper/crow08evolang7th.html}
}