 Theories of cultural evolution need to be distinguished from theories within evolutionary psychology, even though both may involve an application of evolutionary ideas to the explanation of cultural phenomena. The evolutionary psychologist (e.g. Tooby and Cosmides 1992) tends to assume that the most important inheritance mechanism in all species—our own included—is genetic inheritance. Evolutionary psychology regards the human mind as evolving through a conventional process of natural selection acting on genetically inherited variation. For example, an evolutionary psychologist might explain the widespread taste among humans for fatty foods in terms of the importance in our species’ distant past of consuming as much fat as possible on those rare occasions when the circumstances presented themselves. Such a hypothesis can also help to explain novel cultural trends: the recent increase in obesity is explained as the result of a novel environmental change—the increased availability of cheap, high-fat foods—acting in concert with a once-adaptive, now dangerous, gustatory preference. So evolutionary psychology is hardly silent about culture and cultural change. Even so, cultural evolutionary theorists tend to place far more stress on the role of non-genetic inheritance, and specifically of cultural inheritance mediated via learning, as a factor playing a positive, creative role in adapting species to their social and biological environments.