New genetic data shows humans and great apes diverged earlier than thought

To calculate when a species diverged, researchers look at the average age of members of the species when they give birth and mutation rates. The older the average age, the more time it takes for mutations to cause changes. Insects that produce offspring in a matter of months, for example, can adapt much more quickly to environmental changes than large animals that produce offspring many years after they themselves are born. To find such data for both chimps and gorillas, the research team worked with many groups in Africa that included studies of the animals that totaled 105 gorillas and 226 chimps. They also looked at fossilized excrement that contained DNA data. In so doing they found that the average age of giving birth for female chimps was 25 years old. They then divided the number of mutations found by the average age of birth to get the mutation rate. In so doing, they found it to be slower than humans, which meant that estimates based on it to calculate divergence times were likely off by as much as a million years.

The end result of the team’s research indicates that humans and chimps likely diverged some seven to eight million years ago, while the divergence of gorillas (which led to both humans and chimps) came approximately eight to nineteen million years ago. To put the numbers in perspective, humans and Neanderthals split just a half to three quarters of a million years ago.