Evolution of UAC Homo-Pan towards Homo sapiens. Science blog 120
Chimpanzees, gorillas and hominids descend from a species known as UAC Homo-Pan (Last Common Antecedent of Hominids and Pan Chimpanzee-Gorillas). In this UAC Homo-Pan, a series of 8 genes were activated in cascade during the last 15 million years, separating the three species and giving rise to the Homo sapiens.
The first one to activate, 15 million years ago, was the RNF213 gene that favors the increase in diameter of the carotid artery and, with it, the increase in blood flow to the brain. This modification together with the disposition of the cranial bones -greater cranial volume- led to the development of brain size, characteristic of hominids and chimpanzees. This resulted in the splitting of the gorillas from the common trunk.
The second genes to activate, 7 million years ago, were the ASPM and ARH1GAP11B genes that favor the growth of nervous ganglia that cause the development of the cerebral cortex – see the dissemination article The origin of the central nervous system – characteristic of the genus Homo, which separated us from the chimpanzees.
The third to activate, 6 million years ago, were the SLC2A1 and SLC2A4 genes that produce a protein that diverts the transport of glucose from the muscles to the brain.
The fourth to activate, 5.5 million years ago, was the HACNS1 gene that intervenes in the development of arms and hands. This modification allows the appearance of the opposable thumb, which favors the use of tools.
The fifth to activate, 3 million years ago, was the MYH16 gene that reduces the size of the jaws, allowing a new increase in cranial size.
The sixth to activate, 2 million years ago, was the SRGAP2 gene that increases neuron prolongation capacity allowing more interneuronal connections, which is characteristic of the genus Homo brain.
The seventh to activate, 1.5 million years ago, was the FOCP2 gene that allows the capacity of articulating words, ability already present in the Homo neanderthalensis.
Finally, the eighth and last to activate 0.5 million years ago, was the gene AMY1 that allows starch digestion. Therefore, the consumption of cereals as a complement to fruit in human diet was able, which lead to the development of agriculture and the replacement of wild fruit and berries collection.