Читать книгу Anthropology For Dummies - Cameron M. Smith - Страница 39

Sometimes groups of living things move from one environment to another, as when air currents carry insects to a distant island, or some subpopulation of a species of squirrel somehow crosses a river and is cut off from its original population. When this happens, new selective pressures (different temperatures, say, in the new region) may reshape the population so much that if it were to rejoin its ancestral population, the two couldn’t interbreed. This event is called speciation, and it’s what most people think of when they think about evolution: one life form gradually changing into another.

Because speciation can take a long time (anywhere from thousands to millions of years), it’s hard to observe. Still, you can see it in the fossil record, where billions of years of Earth life have left traces of their change through time. And that record speaks clearly, even though it has gaps here and there (because geological forces have wiped out some fossils, for example, or animal and plant remains simply didn’t fossilize due to geochemical factors). All of this tells anthropologists that yes, all living species have long evolutionary histories, including Homo sapiens and all its living and past relatives in the primate order. This is where physical anthropology comes in, to investigate that evolutionary past.