Origin Story: A Big History of Everything

by David Christian

But in 1968, two geneticists, Vincent Sarich and Allan Wilson, showed that we could estimate when two species diverged by comparing the DNA of species that are alive today. This is because large stretches of DNA, particularly those parts that do not code for genes, change randomly and at a relatively consistent pace. Genetic comparisons using these insights showed that humans, chimps, and gorillas shared a common ancestor until about eight million years ago, at which point the ancestors of modern gorillas decided to go their merry way. Humans and chimps shared a common ancestor up to about six or seven million years ago. In other words, somewhere in Africa six or seven million years ago, there existed a creature from which modern humans and chimpanzees are both descended. We do not yet have fossil remains of this creature, but modern genetics tells us it was really there.