The story of world civilizations really begins six to eight million years ago when ancestors of modern humans began to walk upright. Millions of years of evolutionary response to changing climates and environment led to the existence of our species, Homo sapiens. While other hominids migrated out of Africa, had language, and made fire and tools, it was Homo sapiens who were able to navigate open oceans and eventually populate the entire planet. Over the last 50,000 years or so, Homo sapiens became modern humans by improving their hunting, their building techniques, their community living, and their food gathering and storage. About 10,000 years ago, the Neolithic Era began. Humans began to live in larger, permanent settlements where a permanent food source needed to be nearby. These were the beginnings of agriculture. This “agricultural revolution” deeply affected gender relationships, class distinctions, and economic priorities as most humans left their foraging days behind them, the importance of which will be discussed in later chapters.