How Do We Know How Long It Took to Grow Up?

As teeth develop, new enamel layers form daily. Scientists used CT-scanning to count the enamel layers on teeth of a Homo sapiens child who lived in northern Africa 160,000 years ago.

The layers show that the teeth were growing and erupting at the same rate as those of seven- to eight-year-old children today, telling us that this fossil human child was growing at the same rate as living humans.