“Human brains outpace chimp brains in the womb.” September 24th, 2012.
Excerpt: “Elucidating these differences in the developmental patterns of brain structure between humans and great apes will provide important clues to understand the remarkable enlargement of the modern human brain and humans’ sophisticated behavior,” Sakai said.
My comment: What seems to be ignored here, is the epigenetic effect of the nutrient chemical docosahexaenoic acid (DHA), and other dietary influences (e.g., choline) on the human brain and on the development of human behavior.
“Just as the influence of diet and pheromones can be in the larval stages or in other developmental stages of insects, it can also be in the pre- and postconception stages of mammals, including humans (Fowden et al., 2006; Mennella, Jagnow, & Beauchamp, 2001). For example, pheromones and nutrition could alter levels of maternal hormones, gestational events, and postnatal outcomes via their direct effect on maternal GnRH and the placenta. The outcomes might not always be positive, which means the possible effects should not be ignored. That would be like ignoring the likely effects of docosahexaenoic acid in the maternal and postnatal diet on LH and on neuronal development in the mammalian brain (Lassek & Gaulin, 2011).” — Kohl (2012)
See also: Sakai et al. (2011) “These results suggest that a less mature and more protracted elaboration of neuronal connections in the prefrontal portion of the developing brain existed in the last common ancestor of chimpanzees and humans, and that this served to enhance the impact of postnatal experiences on neuronal connectivity.”
My comment: What they are indicating is that the epigenetic effects of maternal nutrition enhance or deter the postnatal epigenetic effects of pheromones on postnatal brain development and behavior.
Sakai et al. (2012) “…we infer that prenatal patterns of human neuronal enhancement changed from those of the chimpanzee during the rapid brain evolution of modern humans [9,10]. These ontogenetic patterns during intrauterine life appear to have emerged after the split of humans from chimpanzees and have contributed to the more marked brain size in our species.”
My comment: Other authors attribute the change to dietary differences, which also contribute to the production of species-specific mixtures of pheromones that control brain development and species specific behaviors — as I detailed in Kohl (2012).