Sunday, October 9, 2011 - 0 comments

The Evolution of Human Birth : 3. Assisted Birth

By : Karen R. Rosenberg and Wenda R. Trevathan

OF COURSE, OUR ANCESTORS and even women today can and do give birth alone successfully. Many fictional accounts portray stalwart peasant women giving birth alone in the fields, perhaps most famously in the novel The Good Earth, by Pearl S. Buck. Such images give the impression that delivering babies is easy. But anthropologists who have studied childbirth in cultures around the world report that these perceptions
are highly romanticized and that human birth is seldom easy and rarely unattended. Today virtually all women in all societies seek assistance at delivery. Even among the !Kung of southern Africa’s Kalahari Desert—who
are well known for viewing solitary birth as a cultural ideal—women do not usually manage to give birth alone until they have delivered several babies at which mothers, sisters or other women are present. So, though rare exceptions do exist, assisted birth comes close to being a universal custom in human cultures.

Knowing this—and believing that this practice is driven by the difficulty and risk that accompany human birth—we began to think that midwifery is not unique to contemporary humans but instead has its roots deep in our ancestry. Our analysis of the birth process throughout human evolution has led us to suggest that the practice of midwifery might have appeared as early as five million years ago, when bipedalism constricted
the size and shape of the pelvis and birth canal.

A behavior pattern as complex as midwifery obviously does not fossilize, but pelvic bones do. The tight fit between the infant’s head and the mother’s birth canal in humans means that the mechanism of birth can be reconstructed if we know the relative sizes of each. Pelvic anatomy is now fairly well known from most time periods in the human fossil record, and we can estimate infant brainand skull size based on our extensive
knowledge of adult skull sizes. (The delicate skulls of infants are not commonly found preserved until the point when humans began to bury their dead about 100,000 years ago.) Knowing the size and shape of the skulls and pelvises has also helped us and other researchers to understand whether infants were born facing forward or backward relative to their mothers—in turn revealing how challenging the birth might have been.

Next : Walking on Two Legs


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