1Department of Anthropology, Boston University, 2Department of Evolutionary Anthropology, Duke University
Thursday 9:45-10:00, Grand Ballroom II
In well-nourished human beings, around 80% of body fat is subcutaneous, with percentages being generally higher in females. In most quadrupedal mammals, subcutaneous fat bodies are much smaller (4% to 30% of total body fat) and scattered. The great majority of body fat in quadrupeds is concentrated in omental and perirenal depots, where its weight is suspended directly from the vertebral column, whereas human omental fat is largely supported from below by the lower body wall and pelvic diaphragm. We suggest that the general transfer of fat deposition in humans from visceral to subcutaneous sites, including specialized cutaneous fat depots in the breasts, buttocks, and proximal limb segments, helps alleviate the increase in caudal intra-abdominal pressure (and corollated increase in the risk of herniation and visceral prolapse) brought about by a shift to exclusively vertical posture. The reduced incidence of inguinal hernias observed in obese males indicates that abdominal cutaneous fat may also help directly to support the abdominal body wall. The proliferation of subcutaneous fat in humans may have evolved as a corollary of the adoption of upright gaits and postures in Pliocene hominins.