When humans first evolved in Africa about 2.5 million years ago, they were no more significant than any other insect or animal. Multiple human species competed for resources with each other and other animals. For many centuries, humans remained solidly in the middle of the food chain; they began to regularly hunt large game about 400,000 years ago and leaped to the top of the food chain about 100,000 years ago. The domestication of fire and the cooking of food allowed the simultaneous development of a shorter digestive tract and a larger brain. Humans’ large brain uses about 25 percent of energy supplies. The combination of cooking, quicker energy absorption through a shorter digestive tract, and large brain resulted in a rapid move to the top of the food chain that was disruptive to the rest of the food chain and to human development as well.

The past 70,000 years have seen three major revolutions in human history: the cognitive revolution, the agricultural revolution, and the scientific revolution. In this short period of time, humans have gone from relative insignificance to the threshold of banishing natural selection.