Researchers have designed a "virtual fossil" of the last common ancestor of modern humans and Neanderthals. Although scientists are aware we share a common ancestor, fossils are scarce so researchers have not been able to get a detailed description of what this prehistoric species would have looked like.

The team have been able to design a 3D skull by applying digital "morphometrics" and statistical algorithms to a variety of cranial fossils from different points in the evolutionary lineage. They managed to create the virtual fossil by noting 797 "landmarks" on craniums that spread over two million years of human history, including a 1.6 million year old fossil of a Neanderthal crania found in Europe.

The landmarks on these fossils were then used to establish an evolutionary framework that allowed the team to predict a timeline for the morphology of the skulls. They then placed a digitally scanned modern skull on the timeline, which changed to fit the landmarks throughout Homo history.

This allowed them to see how the morphology of both species converged during the time the common ancestor would have lived - 800,000 to 100,000 years ago in an era known as the Middle Pleistocene. Three possible skulls were created which they used to predict the split between Homo sapiens and Neanderthals.

virtual fossils
Top to bottom: Modern human skull, 'Virtual fossil' of Last Common Ancestor, Neanderthal skull found in La Ferrassie, FranceDr. Aurélien Mounier

By doing this, the researchers were able to gain a better understanding of which was the best fit. They concluded there was a lineage split around 700,000 years ago, dwarfing previous estimates of 400,000 years. They were also able to state that it would have originated from Africa, according to the study published in the Journal of Human Evolution.

"We know we share a common ancestor with Neanderthals, but what did it look like? And how do we know the rare fragments of fossil we find are truly from this past ancestral population? Many controversies in human evolution arise from these uncertainties," said the study's lead author, Dr Aurélien Mounier, a researcher at Cambridge University's Leverhulme Centre for Human Evolutionary Studies (LCHES).

"We wanted to try an innovative solution to deal with the imperfections of the fossil record: a combination of 3D digital methods and statistical estimation techniques. This allowed us to predict mathematically and then recreate virtually skull fossils of the last common ancestor of modern humans and Neanderthals, using a simple and consensual 'tree of life' for the genus Homo."

There would have been a prominent bulge at the back of the skull, they say, but that there would have been strong indentation under the cheekbones that would have given it delicate facial features like modern humans.