The postnatal life cycle of the social mammals, including the nonhuman primates, has three basic stages of development: infant, juvenile, and adult. Human beings are unusual and add a childhood stage after infancy and an adolescence stage after the juvenile stage. The human pattern of life history in both brain and body growth entails a large investment of energy and time by older members of the social group toward infants and children. This is achieved via a new type of breeding strategy called biocultural reproduction. The evolution of human life history results in enhanced reproductive success for the individuals and our species.
The amygdala is a telencephalic structure that plays an essential role in emotions, social behavior, and social cognition, representing a central hub for the neural networks involved in these functions. However, its homology in nonmammals, particularly in sauropsids, has been controversial. We use an evolutionary developmental biology approach for trying to deconstruct this complex structure into its basic components (based on embryonic origin and molecular profile), decipher the organization of its functional networks, and analyze evolutionary trends throughout vertebrates. Major events occurred during the anamniote–amniote transition, involving the incorporation of new cell types and perhaps the development of on/off functional systems related to a more sophisticated and plastic control of emotions, social behavior, and cognition.
