Laboring Humans

The human birth process and the developmental state of the infant at birth are direct legacies of significant aspects of our evolutionary history over the last five million years. Specifically, this includes: our bipedal form of locomotion, the large overall body size of our infants at birth relative to the body sizes of the mothers who give birth to them, our encephalized (large brained) newborns, the relatively helpless state in which these large babies arrive and the duration of time for which they remain helpless and dependent after being born. We know from the human fossil record that these aspects of our biology evolved in a mosaic fashion, at different points in time over the last five million years of our evolutionary history.  For example, bipedalism evolved as the human mode of locomotion long before our brains became dramatically larger, and the other features mentioned above probably evolved after that, but before 100,000 years ago. All of these adaptations have important consequences for the reproductive lives and life histories of humans today. Our lives as mothers and allomothers (individuals other than the biological mother who provide maternal care) are shaped by the constraints of bearing, carrying (both in and ex utero) and caring for our uniquely large and helpless children, who have themselves evolved to demand and receive high levels of attention from adults. I argue here that our adaptations to these mechanical, physical and biological constraints are cultural and social, often involving assistance by kin or non-kin and comprise some of the most important aspects of our humanness. The benefit of help to mothers occurs throughout our life histories including: assistance during pregnancy, childbirth and lactation, help in care, carrying and feeding of dependent offspring and ultimately even adoption of orphaned children.