ABSTRACT
This chapter considers the phylogenetic background of human birth and bonding. It suggests that sexual reproduction conveys advantages on practitioners in that greater variation in offspring, resulting from meiotic division and recombination, provides greater flexibility in responding to environmental change. After sexual reproduction, the next adaptations of concern in the evolution of the human reproductive strategy are the steps of internal fertilization and internal gestation, or the evolution of viviparity from the primitive oviparous baseline. Mammals with hemochorial placentas and very short gestation times could also experience rapid diversification of lines because birth occurs before immunological rejection can occur. The chapter describes factors in human evolutionary history that have contributed to increasing altriciality of the hominid infant. The course of human evolution has been dominated by two trends: increasing brain size and increasing efficiency of bipedal locomotion. The chapter presents an overview of the key concepts discussed in the subsequent chapters of this book.
