There are lots of theories about what caused human evolution. Here’s a new one: cooking!
When humans invented cooking, it increased the number of calories they consumed, since heat breaks down cellulose in plants, making them more digestible and releasing the nutrients. Before the discovery of fire, we would have had to forage for 9 hours a day in order to get the same number of calories.
This could be the reason that other primates, such as gorillas, may have bodies 3 times larger than ours, but still have much smaller brains, despite the fact that they spent almost 8 hours a day foraging for food.
Studying the Medieval skeletons of people who went through the European plague (also called the Black Death), which killed 30% of Europeans, including nearly half of the people in London, between 1347 and 1351, may help us understand how disease can affect human evolution.
Anthropologist Sharon DeWitte says that these skeletons "can tell us something about the nature of human variation today and whether there is an artifact of diseases we have faced in the past. Knowing how strongly these diseases can actually shape human biology can give us tools to work with in the future to understand disease and how it might affect us."
Evolution doesn’t happen overnight: large changes in body size take a long time. There have been increases and decreases in mammal size following the extinction of the dinosaurs 65 million years ago. Now biologists estimate that a mouse-to-elephant size change would take at least 24 million generations, based on the maximum speed of evolution in the fossil record.
PhysOrg.com quotes researcher Alistair Evans as saying, "A less dramatic change, such as rabbit-sized to elephant-sized, takes 10 million generations."Huge sea mammals, such as whales, took about half that number of generations to reach their current size.