Last Thursday, October 17th, the US journal Science published shocking findings by a Georgian team of scientists, regarding an eight-year study on a fossilized skull from 1.8 million years ago.
The discovery? The evolutionary history of our human genus Homo may have a simpler family tree with fewer ancestral species, according to the team led by David Lordkipanidze, a paleoanthropologist at the Georgian National Museum in Tbilisi.
The findings suggest that early hominids’ bone structures were as diverse as people today. The dissimilarity of the bones they left behind may have fooled scientists into thinking they came from different species, as they could actually represent variation among members of a single, evolving lineage.
In other words, one skull has forced scientists to rethink human evolution.
These remains are thought to be early forms of Homo erectus, the first of our relatives to have body proportions like a modern human. This species may have been the first to harness fire and cook food.
The pinnacle of the find, “Skull 5”, is a skull excavated from the ancient remains of the ancient town Dmanisi, just 62 miles southwest of the capital Tbilisi. It’s the first completely preserved skull found from the early Pleistocene period, when our predecessors first walked out of Africa.
The skull has an almost-complete set of teeth, and appears to be more elongated than a normal human skull. It’s about a third the size of a modern human head, and has the smallest braincase of the five individuals found at the site.
The odd dimensions of Skull 5 prompted the team to look at normal skull variation in modern humans, chimps, and supposedly different species of human ancestor that lived in Africa at the time to see how they all compared. They concluded that even though each Dmanisi skull looked different, the variations were no greater than those seen among modern people and chimps.
If the scientists are right, the human ancestors found in Africa from the same period may simply be normal variants of Homo erectus. This means that the human evolutionary tree would be cut at the roots, spelling the end for names such as H rudolfensis, H gautengensis, H ergaster and H habilis.
This discovery, while extremely fascinating and important, has also built up much controversy in the scientific community.
Dr. Christoph Zollikofer of the University of Zurich advocated to the NY Times, “Since we see a similar pattern and range of variation in the African fossil record, it is sensible to assume that there was a single Homo species at that time in Africa.” He added, “since the Dmanisi hominids are so similar to the African ones, we further assume that they both represent the same species.”
Lordkipanidze’s analysis casts doubts on other scientists’ theories, and as a result, they do not support the new findings. Lee Berger, from University of Witwatersrand, claims that a creature called Australopithecus sediba lived in what is now South Africa around 1.9m years ago and was a direct ancestor of modern humans. He argues that it was premature to dismiss his findings and criticized Lordkipanidze’s team for failing to compare their fossils with the remains of A sediba.
Berger told the Guardian, “This is a fantastic and important discovery, but I don’t think the evidence they have lives up to this broad claim they are making. They say this falsifies that Australopithecus sediba is the ancestor of Homo. The very simple response is: no it doesn’t.”
He continued to say, “What all this screams out for is more and better specimens. We need skeletons, more complete material, so we can look at them from head to toe. Any time a scientist says ‘we’ve got this figured out’ they are probably wrong. It’s not the end of the story.”