Sunday, October 9, 2011 - 0 comments

The Evolution of Human Birth : 1. Preview

By : Karen R. Rosenberg and Wenda R. Trevathan

The difficulties of childbirth have probably challenged humans and their ancestors for millions of years—which means that the modern custom of seeking assistance during delivery may have similarly ancient roots.

GIVING BIRTH IN THE TREETOPS is not the normal human way of doing things, but that is exactly what Sophia Pedro was forced to do during the height of the floods that ravaged southern Mozambique in March 2000. Pedro had survived for four days perched high above the raging floodwaters that killed more than 700 people in the region. The day after her delivery, television broadcasts and newspapers all over the world featured images of Pedro and her newborn child being plucked from the tree during a dramatic helicopter rescue. Treetop delivery rooms are unusual for humans but not for other primate species. For millions of
years, primates have secluded themselves in treetops or bushes to give birth. Human beings are the only primate species that regularly seeks assistance during labor and delivery. So when and why did our female ancestors abandon their unassisted andsolitary habit? The answers lie in the difficult and risky nature of human birth.

Many women know from experience that pushing a baby through the birth canal is no easy task. It’s the price we pay for our large brains and intelligence: humans have exceptionally big heads relative to the size of their bodies. Those who have delved deeper into the subject know that the opening in the human pelvis
through which the baby must pass is limited in size by our upright posture. But only recently have anthropologists begun to realize that the complex twists and turns that human babies make as they
travel through the birth canal have troubled humans and their ancestors for at least 100,000 years. Fossil clues also indicate that anatomy, not just our social nature, has led human mothers—in contrast
to our closest primate relatives and almost all other mammals—to ask for help during childbirth. Indeed, this practice of seeking assistance may have been in place when the earliest members of our genus, Homo, emerged and may possibly date back to five million years ago, when our ancestors first began to walk upright
on a regular basis.

Next : Tight Squeeze


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