Another best guess is that our ancestors spent on the order of the last 4 million years as pre-sapient hominids. For those 4 million years, the problems they had to face-the selective pressures that shaped their actions and cognition-were something like the problems faced by (AL) 288-1 ("Lucy") or KNM-ER 3733 (the Koobi Fora Homo erectus). That fact has inspired more than a few anthropologists to look for the roots of human behavior in Pleistocene woman and man-and in their supposed living analogues, the Kalahari !Kung. We moderns, by their logic, must be something like Koobi Fora or Botswana hunters and gatherers. The conclusions drawn are the same. Understanding modern human thought or behavior means understanding what raised fitness in foragers, then understanding culture, and then trying to put them together (e.g., Lee & DeVore, 1968; many recent examples include Barkow, Cosmides, & Tooby, 1992; Smith, 1992; Symons, 1979).