Discernment of mortality risk associated with childbirth in archaeologically derived forager skeletons.

An obstetric dilemma may have been a persistent characteristic of human evolution, in which the bipedal female's pelvis is barely large enough to accommodate the birth of a large-brained neonate. Evidence in the archaeological record for mortality risk associated with childbirth is rare, especially among highly mobile, immediate return hunter-gatherer populations. This research explores the idea that if excess mortality is associated with first pregnancy, females will outnumber males among young adult skeletons. The sample is of 246 skeletons (119 males, 127 females) representing Later Stone Age (LSA) foragers of the South African Cape. Young adults are distinguished through incomplete maturation of the medial clavicle, iliac crest and vertebral bodies. With 26 women and 14 men in the young category, a higher mortality risk for women is suggested, particularly in the Southern Cape region. Body size does not distinguish mortality groups; there is evidence of a dietary protein difference between young and older women from the Southern Cape. Possible increased mortality associated with first parturition may have been linked to morphological or energetic challenges, or a combination of both. Exploration of the sex ratio among young adult skeletons provides a tool for exploring the antiquity of an important evolutionary factor.