Evolution takes place because we successfully adapt to changes in our environments over vast amounts of time, leading to the false belief that evolution occurs only when the environmental change is stable over time so that the adaptive changes can take hold and the species can flourish. After all, if the adaptative pressure goes in one direction and then reverses course, the adaptive changes might never happen or become maladaptive and cause extinction. But the climatic record during human evolution has been extremely variable, especially in the recent past, so it does not support the idea that environmental stability produced our adaptation. This post will discuss the accepted definition of ice ages, glaciations, interglacials, and their effect on human evolution.
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