In previous chapters, we saw that modern humans are a highly generalized species. This means that we can live in a great variety of climates, eat a wide variety of foods, and respond to most environmental challenges in myriad ways. For example, as human populations moved into cold northern climates, they were able to respond both physiologically and behaviorally to the environmental challenges they faced. As noted previously, adaptations to cold include physiological responses to conserve or increase heat, such as vasoconstriction of the capillaries, increased metabolic rate, and shivering. Considering these responses from an evolutionary perspective, we can assume that, among the earliest human populations inhabiting cold regions of the world, those individuals who had genotypes and phenotypes enabling them to respond physiologically had more surviving offspring to pass along these characteristics. Behavioral and cultural adaptations to cold climates probably included fire, house structures, warm clothing, and hunting for foods that provided energy to withstand the cold. In these examples we see evidence of human adaptations to cold that are both biological and cultural and are rooted in evolution.
A concern we have today, however, is that the environments inhabitedby humans are changing at rates far exceeding thoalso appears to have droppedse experienced by previous generations. In fact, the human environment has changed more radically in the last few decades than it has at any point in the entire course of human evolutionary history. What are the consequences of these tremendous changes, some of which you have seen in your own lifetime? In this chapter and the next, we’ll explore ways in which the legacies of human evolution continue to have profound impacts on our biology and behavior throughout our lives and on the planet we inhabit even in the face of ever-increasing rates of cultural and technological change.