The Evolution of the Primate, Hominid and Human Brain

Human evolution involved four brain enhancement steps. The first step of brain size enhancement occurred in lower simian primates (brain size 0.17%-0.19% of body weight). The second step occurred in advanced simian primates (brain size 0.66%-0.78% of body weight). The third step occurred among early hominids (brain size 1.0%- 1.2% of body weight), and the fourth of final step occurred among humanoids (brain size 2.1%-2.7% of body weight). This brain enhancement occurred in response to brain growth genes or brain growth factor proteins. Brain growth was very much limited by the efficiency of fetal nutrition or placentation. In many respects it was the efficiency of placentation and implantation that controlled brain growth genes expanding brain growth to the limit that placentation could allow. Brain growth was initially blocked by inefficiency of epitheliochorial placentation. It was the initial evolution of chorionic gonadotropin (CG) and hyperglycosylated CG that promoted the creation of hemochorial placentation, and the implantation of the placenta. This occurred in lower simian primates and so was followed by initial implantation and hemochorial placentation. This permitted the first step in brain growth. The CG gene underwent mutation with advanced simian primates and a higher biological activity CG and hyperglycosylated hCG resulted. This drove more efficient implantation and placentation and so primates developed a bigger brain, the second step in brain growth. The CG gene underwent further mutation with early hominids and a higher biological activity CG and hyperglycosylated hCG resulted. This drove even more efficient implantation and placentation and so early hominids developed a bigger brain, the third step in brain growth. The CG gene underwent mutation with humanoids and a higher biological activity CG and hyperglycosylated hCG resulted. This drove the most efficient implantation and placentation and so humanoids developed the biggest brain, the fourth step in brain growth.