Evolution of Primate Intelligence

Recently , diet , life span and population density were associated to directly act on primate brain sizes , especially the neocortex (Walker et al , 2006 . Mechanisms behind such increase in size involves generation of a large brain which consequently programs the body to increase food intake and lengthen its life span to be able to substantially maintain and develop a bigger brain . The brain has also evolved to accommodate changes for social interactions (Dunbar and Shultz , 2007

Sexual selection is also involved in the evolution of bigger brains sizes mainly through a negative

feedback relationship with male competition for mates (Schillaci 2006 . Sperm competition , as determined by measurement of primate testis , was determined not to play a role in primate brain evolution . In addition , monogamous mating which involves more effort in social acuity and deception capabilities is associated with larger brain sizes

Comparative gene expression studies in several anthropoid species have shown that enormous amounts of energy is metabolized by neurons of the neurocortex , mainly due to the significantly high numbers of glial cells in the frontal cortex of humans , as compared to that of other primates (Sherwood et al . 2006 . However , brain regions responsible for cognition and language did not have substantially greater energy requirements for metabolism than in other primates , suggesting that the energy needed by the human brain in mainly for neuron expansion and projection of axons and dendrites

At the genetic level , the gene microcephalin (MCPH1 ) was observed to have undergone positive selection across the hominoid lineage , resulting in a human-specific haplotype that is observed at an allele frequency of 0 .70 (Evans et al . 2006 . This recent haplotype emerged 1 .1 million years ago (mya ) and was distributed throughout the rest of the human race approximately 37 ,000 years ago , suggesting an admixture between early and modern...