About six million years ago, the earliest people evolved from earlier primates in East Africa. People may have evolved in order to take advantage of new grasslands or new wetlands that were taking over from the jungle in Africa beginning about eight million years ago as the Earth cooled down. Very soon, these people began to walk on two feet, and their arms became weaker and shorter, as they spent less time swinging from tree branches. That might have been so they could run faster in the grasslands to hunt animals. Or it might have been so they could swim and wade across lakes. More and more, these people slept on the ground, in groups, instead of in the trees, and they slept more deeply, for fewer hours. They dreamed more.
These first people were still pretty hairy, like monkeys, and had small brains. Possibly they continued to have babies with other primates like chimpanzees sometimes for another million years. They probably ate mostly fruit, like chimpanzees, but also roots like yams, nuts, insects, meat, and a lot of fish and shellfish.
By about two million years ago, modern humans were beginning to evolve. They lost their body hair and developed black skin to protect them from the sun. They began to have bigger brains. Their tongues and throats evolved so that they could talk. About one million years ago, people figured out how to make fires to cook their food and keep warm.
About 60,000 BC, when the first humans began to live further north, in Europe and Asia, to keep warm they had to re-evolve some of the body hair they had lost in Africa. They also re-evolved the pink skin of other primates, so that they could absorb more Vitamin D from the smaller amount of sunlight they had. When humans first began to keep cattle and sheep, about 6000 BC, some of them evolved the ability to digest milk. That’s why some people can digest milk and others can’t. People are still evolving today, though it happens so slowly that it’s hard for us to see.
Learn by doing: start a campfire from coals or with a match
More about the Quaternary period