The first wave of colonization by Homo sapiens was one of the biggest and fastest ecological catastrophes in the animal kingdom  Among the hardest hit are the large animals  At the time of the cognitive revolution, there were about 200 genera of large land mammals weighing more than 50 kilograms  By the time of the agricultural Revolution there were only about 100 genera left
After the cognitive revolution, the earth's climate has appeared many cooling and warming cycles with large variation range
 In other words, long before humans invented the wheel, writing or iron, homo sapiens wiped out about half of the world's great beasts