YEARBOOK OF PHYSICAL ANTHROPOLOGY [Vol. 40, 1997
Evolutionary Hypotheses for Human Childhood
BARRY BOGIN Department of Behavioral Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128
This is an intriguing and very readable paper that delineates clear differences in thought regarding the evolution of Homo sapiens. Bogin rejects non-reproduction-based explanations (welcome surprise!) for the “appearance” of extended infancy, childhood and juvenile stages of development. He rejects neoteny or heterochrony as sole mechanisms to account for unique aspects of human development; however, some of his claims are simply wrong regarding human uniqueness – and, within his hypothesis, there is nothing to rule out heterochrony and neoteny as critical mechanisms behind the addition or extension of the human infant-child-juvenile sequence of development.
My emphasis in this blog is on sexual selection for tameness / domestication due to the shift to agriculture from hunting, foraging, scavenging and gathering (nomadism). The inevitable sedentary-urban lifestyle that the new dependence on less nutritious food, and the increase in labor required for food production, necessitated adaptations that we see in a neotenic modern social type that dominates today. Many steps involving differential evolution of brain function, reproduction, behavior, culture and physiology have likely taken place to produce Homo sapiens sapiens (neurotypical humans).
I’d like to comment point by point, but this is a long essay…
Evolutionary Hypotheses for Human Childhood (1997)
BARRY BOGIN Department of Behavioral Sciences, University of Michigan-Dearborn, Dearborn, Michigan
The origins of human childhood have fascinated scholars from many disciplines. Some researchers argue that childhood, and many other human characteristics, evolved by heterochrony, an evolutionary process that alters the timing of growth stages from ancestors to their descendants. Other scholars argue against heterochrony, but so far have not offered a well-developed alternative hypothesis. This essay presents such an alternative.
Childhood is deﬁned as a unique developmental stage of humans. Childhood is the period following infancy, when the youngster is weaned from nursing but still depends on older people for feeding and protection. The biological constraints of childhood, which include an immature dentition, a small digestive system, and a calorie-demanding brain that is both relatively large and growing rapidly, necessitate the care and feeding that older individuals must provide.
Evidence is presented that childhood evolved as a new stage hominid life history, ﬁrst appearing, perhaps, during the time of Homo habilis. The value of childhood is often ascribed to learning many aspects of human culture. It is certainly true that childhood provides ‘‘extra’’ time for brain development and learning. However, the initial selective value of childhood may be more closely related to parental strategies to increase reproductive success. Childhood allows a woman to give birth to new offspring and provide care for existing dependent young. Understanding the nature of childhood helps to explain why humans have lengthy development and low fertility, but greater reproductive success than any other species. Yrbk Phys Anthropol 40:63–89, 1997. r 1997 Wiley-Liss, Inc.
Childhood fascinates scholars and practitioners from many disciplines. Virtually all human cultures recognize a time of life that may be called ‘‘childhood.’’ Many historical sources from Egyptian times to the 19th century, including Wordsworth in the poem above, mention that ‘‘childhood’’occupies the ﬁrst 6 to 7 years of life (Boyd, 1980). Some explanations for the origins and functions of childhood have been proposed, but none of these is accepted universally. Perhaps the lack of agreement is due to the nature of human evolutionary biology.
Much, much more…..
Orangutans hanging out, from James Tan.
There are a lot of conflicting claims about “childhood” and other aspects of comparative primate development…… The orangutan has the longest childhood dependence on the mother of any animal in the world, because there is so much for a young orangutan to learn in order to survive. The babies nurse until they are about six years of age….Orangutan females only give birth about once every 8 years – the longest time between births of any mammal on earth. (This results in only 4 to 5 babies in her lifetime.) This is why orangutan populations are very slow to recover from disturbance.