Friday, July 22, 2011

Obstetrical Dilemmas and Human Culture

The so-called "obstetrical dilemma" is an area of great interest to several subfields of anthropologists, because it appears to have initiated a concatenating series of effects on human behavior. In short, this dilemma is caused by the constriction of the pelvic opening as a result of the shift to bipedal locomotion. In order for hominins to walk upright, this pelvic opening, also called the pelvic girdle, has become smaller. This means that considerably less room was left for an infant's head to pass through the pelvis during birth. Accordingly, the size of the infant's head has an upper limit, or the baby can't be born, and both mother and child will die during childbirth.

However, the development of bipedal locomotion has resulting in increased opportunity to access a more diverse, and calorie dense, set of food resources, specifically more protein. One side effect of this is increased brain development, for several reasons: one, if you can get more calories, then your body can allocate more energy to developing a bigger brain; and two, if you are eating a more diverse collection of foods, you'll probably be more motivated to develop tools and strategies to consume them once you've walked or run there. So, more diverse foods and more tool use equals a bigger brain, but the foundation for these behaviors - bipedalism - equals smaller pelvic girdles. Clearly, this is a problem.

This means that human infants must be born at a very early stage, developmentally speaking. It is no exaggeration to say that a human infant is essentially still a fetus, given how completely helpless s/he is, and how dependent s/he is on her or his mother. A newborn human infant can't even cling onto his or her mother effectively until months after birth, and therefore must be carried by the mother. Further, s/he must be fed every two hours (in some cases, more). For a human infant to survive, the mother must focus a considerable amount of effort on the baby, night and day.

Human mothers must also have help to give birth, generally speaking. In some cases, this even involves dramatic surgical interventions like C-sections. At minimum, a human mother generally requires a birth attendant who can help deliver the infant and assist the mother, whose body must go through considerable trauma to successfully give birth to her child. In most cultures, these attendants are other women who specialize in this; these are midwives in our culture, and even today, many women in our society give birth with midwives in attendance (many of whom are also nurses or otherwise trained in modern Western medicine).

Some anthropologists think that these effects have had considerable impacts on human cultural developments. In 1996, Trevathan argued that birth in the bipedal hominin must needs be a social event, and that this difference from non-bipeds is at the root of a lot of culture (for full access to the Trevathan paper, you must have full access to JSTOR). Certainly, if you consider that a considerable portion of a population - pregnant and laboring females, as well as their small offspring - would need social support to survive, it's reasonable to speculate on the different social mechanisms that might develop to help achieve this goal.

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