Guns, Germs, and Steel

This onset of major human advancement involved geographical expansion to Australia and New Guinea and occurred around 50,000 years ago. With this leap came the geographical expansion of the human population: Evidence shows that human beings originated in Africa, but evolution led to people migrating into different territories. The Great Leap also peopled the coldest parts of Eurasia. 

Hunter-gatherers turned to food production whenever they could, based on geographic and environmental factors. The first factor that prompted a shift towards farming was a decline in the availability of wild foods and animals, or even animal extinction—this would reward domesticating wild plants. Another influence was the development of technologies for collecting, processing, and storing wild foods. A final factor came into play once the population of food-producing areas had grown in density. Though sheer numbers, food producers were able to displace or kill remaining hunter-gatherers.

Plant domestication involves growing a plant and causing it to change genetically from its wild ancestor. Some plants were seen as easier or more inviting to domesticate than others. Animal domestication means breeding animals in captivity and over time selecting for traits that will render the animal different from its wild ancestors. These traits could be size, greater retention of wool, higher milk yields, smaller brains, and less developed sense organs.