MMW 11 Chapter Notes - Chapter Essays: 6-8: Australopithecus, Homo Erectus, Color Vision

• School: UCSD
• Department: Making of the Modern World
• Course: MMW 11
• Professor: David Jordan

Document Summary

Sourcebook evolution essay 6 (human birth and bipedalism) notes: Human bipedalism done by narrow pelvis, yet must be large enough to accommodate birth. Male pelvis is much narrower than females: narrowest part of female pelvis is pelvic inlet. Two factors make human birth possible: mother releases hormones relaxing pubic symphysis and sacroiliac symphyses. Symphyses meeting point of tow bones: baby"s head is flexible enough to compact slightly, on premature babies, the head is smaller but also weaker, risking brain damage. As head comes out of pelvic outlet, shoulders must squeeze through pelvic inlet. Baby comes out facing the floor if mother is on her back: if mother tries to speed process up by pulling the baby out, the baby"s spine may be permanently damaged. Babies may be delivered via cesarean section: hole cut into abdominal wall of mother and baby is taken out that way. Longer gestation (period in womb) correlates with shorter time to maturity.