For most of Homo sapiens' time out of Africa, we lived in a world defined by ice. But by around 20,000 years ago, the ice had begun to melt, the glaciers retreating back toward the poles and mountain ranges. This left behind a new world, a whole different series of environments, opportunities, and perils for the people who had made it through the Ice Age.Support us by supporting our sponsors!SimpliSafe - Get FREE shipping and a 60 day risk free trial when you got to simplisafe.com/tides. Great Courses Plus - Visit thegreatcoursesplus.com/tides to access to the entire library for FREE. See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.