From <a href="http://www.lehigh.edu/~dmd1/art.html" rel="nofollow">http://www.lehigh.edu/~dmd1/art.html</a> (just somebody's term paper I found on Google):<p><i>The Tarahumara are not very hygienic to even modern day indigenous standards. They are not very cleanly and the washing of their clothes is usually either an annual or semiannual tradition. The Tarahumara have no regular sleeping habits and simply go to sleep whenever and wherever they are tired and feel that they need rest. The practice of childbirth is also distinct to the Tarahumara. When a woman feels that it is about time for her to deliver the baby she will go off by herself into the wilderness, brace herself between two small trees and attempts to have the baby safely. There is a very high infant mortality rate among the Tarahumara. This fact is counterbalanced by the fact that there is also a very high birth rate. The average Tarahumara woman gives birth to about ten babies hoping that three or four will survive into adulthood. Adulthood is usually short for the Tarahumara with the average life expectancy being forty-five (Lutz 50). These factors are believed to help the Tarahumara survive as a race.</i><p>Perhaps the reason they have low incidence of diabetes, cancer, and heart disease is that these ailments often set in after the age of 45?