Then the scientists placed all of these living and extinct individuals on an evolutionary tree. In doing so, they were able to trace the evolution of skulls along each of the branches, arriving at a picture of the skull of the common ancestor of living humans.
“More or less, it’s quite a modern human,” Mounier said of the skull. “But it doesn’t really correspond to any current population – it’s something different.”
The rendering of this ancestral skull shows the same vaulted braincase that we have today. But it also has heavier brow ridges and a protruding lower face.
Dr. Mounier and Dr. Lahr compared their ancestral skull with real African fossil skulls from the same period. The researchers found a number of differences – so many, in fact, that they think the fossils belong not to a single population, but to three.
The Moroccan fossil belongs to one population. Another fossil, found in Tanzania, represents the second. The third population includes two fossils from two sites that are thousands of miles apart: South Africa and Kenya. This third population, the researchers concluded, most closely resembles the ancestor of modern humans.
The evolutionary lineage that gave rise to modern humans produced a number of populations across Africa around 350, 00 0 years ago, Dr. Mounier and Dr. Lahr speculate. These humans all had big brains and made increasingly sophisticated tools.