PRIMATE BRAIN EVOLUTION - GENETIC AND FUNCTIONAL CONSIDERATIONS

Functionally distinct regions of the brain to which maternal and pater nal genomes contribute differentially (through genomic imprinting) hav e developed differentially over phylogenetic time. While certain regio ns of the primate forebrain (neocortex, striatum) have expanded relati ve to the rest of the brain, other forebrain regions have contracted i n size (hypothalamus, septum). Areas of relative expansion are those t o which the maternal genome makes a substantial developmental contribu tion. This may be significant with respect to the importance of primat e forebrain expansion in the development of complex behavioural strate gies and the way in which these are deployed, especially by the matril ine. In many primate societies the maintenance of social cohesion and group continuity over successive generations is dependent on the matri line, with high ranking females producing high ranking daughters that stay within the group. Regions of relative contraction are those to wh ich the paternal genome makes a differential contribution and these ar e target areas for gonadal hormones, which is congruent with the dimin ished role for gonadal hormones in the emancipation of primate reprodu ctive behaviour.