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Homo Neanderthalensis.

Homo Neanderthalensis.

The evolution of humanity is a long and complicated path that spirals through prehistory, and is likely a mystery that will never conclusively be solved. What we currently know about the process is based on the handfuls of fossils that we’ve found, and our ability to connect those fossils together and discover the common links between members of the Homo family. It is estimated that our closest prehistoric relative, Homo Neanderthalensis, became extinct about 40,000 years ago–however, scientifically we know that we share a common, undiscovered ancestor. Exactly what our ancient ancestor actually looked like or what connections it would have to us are unknown due to the scarcity of fossil evidence of the lineage split estimated to have happened during the Middle Pleistocene period.

A team of researchers, lead by Cambridge University’s Leverhulme Centre for Human Evolutionary Studies (LCHES) Dr. Aurélien Mounier, have created a virtual fossil that may have just put a face to our lost family member. The researchers combined 3D scans of several fossil skulls and modern human skulls and applied advanced digital ‘morphometrics’ and a series of statistical algorithms to them. This resulted in the creation of a 3D ‘virtual fossil’ that they believe is the very last common ancestor of Homo sapiens and Neanderthals.

The last common ancestor.

The last common ancestor.

The simulated fossil was generated by plotting 797 evolutionary landmarks on the crania of numerous fossil skulls that date back through the two million years of Homo ancestry. The 3D scanned skulls included a 1.6 million year old Homo erectus fossil, a Neanderthal cranium found in Europe and several 19th century skulls on loan from the Duckworth collection in Cambridge. By cataloging the landmarks on the skulls, researchers were able to create a morphology of our evolutionary ancestors, essentially creating a framework that allowed them to predict the timeline for the evolving structure of the pre-human skulls.

Timeline for the split between Homo Sapiens and Homo Neanderthalensis.

Timeline for the split between Homo Sapiens and Homo Neanderthalensis.

By combining this timeline with a modern 3D scanned human skull they were able to warp it to conform to the evolutionary framework they developed. The team essentially went back in time to when Homo sapiens and Neanderthals may have become two different species during the Middle Pleistocene era, about 800,000 to 100,000 years ago. The resulting data allowed the researchers to create three possible ancestral skulls that matched up with three potential evolutionary splits between both species. They rendered virtual fossils of each of the three options and compared them to the few existing bone fragments that exist from the Pleistocene age. This allowed them to further narrow down the virtual skull to the one that was most likely our last common ancestor to Neanderthals.

“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. 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,” Mounier explained in his study.

The Homo family timeline.

The Homo family timeline.

Using ancient DNA material, evolutionary scientists previously estimated that our last common ancestor to Neanderthals lived about 400,000 years ago. Amazingly, what the researchers discovered once they compared their ‘virtual fossil’ to existing Middle Pleistocene fossil fragments is that the lineage split most likely occurred more than 700,000 years ago.That difference of 300,000 years changes the entire evolutionary timeline that scientists have been working from for decades. It also alters the perception of exactly where modern human ancestors came from. While there is some evidence that this ancestor was present in limited numbers throughout Eurasia, the last common ancestor was probably most prominent on the African continent, where it would have originated.

Here is a brief video demonstrating the process of creating the virtual fossil:

The virtual skull fossil reveals that the common ancestor has features that are reminiscent of both Homo sapiens and Neanderthals. The similarities include an early budding of the ‘occipital bun’, a prominent bulge at the base of the Neanderthals skull, and the strong cheekbone indentation that gives humans their more delicate features. The skull also features a thickset brow that was characteristic of early Homo species and Neanderthals but lost to modern humans. According to Mounier this was unsurprising as Homo sapiens deviated from the ancestral trajectory in several prominent ways, including skull structure.

[Top] human, [center] virtual fossil, [bottom] Neanderthals.

[Top] human, [center] virtual fossil, [bottom] Neanderthals.

“The possibility of a higher rate of morphological change in the modern human lineage suggested by our results would be consistent with periods of major demographic change and genetic drift, which is part of the history of a species that went from being a small population in Africa to more than seven billion people today,” said LCHES researcher Dr. Marta Mirazón Lahr, who co-authored the published paper on the virtual fossil with Mounier.

The results of the study and the creation of the virtual fossil were published in the Journal of Human Evolution. Mounier and his team are already hard at work planning their next project. Using the same digital ‘morphometrics’ and statistical algorithms, they plan to discover the last common ancestor that connects the earliest Homo with chimpanzees.  Let’s hear your thoughts on this approach in the 3D Scanning our Ancestors forum thread on 3DPB.com.

[Images: Dr. Aurélien Mounier / Source: Daily Mail]

 

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