The evolutionary masquerade: genetic and epigenetic contributions to the neocortex

- Organisms rapidly change within a lifetime and across generations.
- Context shapes the neocortical phenotype in mammals, including humans.
- Epigenetic mechanisms may mediate contextual effects on the neocortical phenotype.
- Humans might be distinguished from other primates on the basis of their epigenome.

The neocortex is a defining feature of the mammalian brain and its expansion is one of the hallmarks of human evolution. Given the complexity of human behavior, it is tempting to think that as a species humans are exclusive compared to other animals. However, comparative studies indicate that human brains follow the same rules of construction and that alterations to the human neocortex take a similar form as in other mammals. Studies from a number of disciplines indicate that many of the morphological specializations associated with the vocal tract, ear and hand were present in early hominins and thus our ancestors had the capacity for speech, language and sophisticated manual abilities, yet much of modern human behavior evolved very recently. In this review, we discuss the possibility that phenotypic changes in modern human brains and behavior may have been mediated by epigenetic mechanisms that allowed for context dependent changes to the cortical phenotype. Further, we consider whether these epigenetic mechanisms may be more readily engaged in humans than in other species in order to rapidly meet the demands of a dynamic environment. We suggest that perhaps it is the extent to which the neocortex incorporates these context dependent alterations that distinguishes humans from other mammals.