1.8-million-year-old skull shakes mankind’s family tree

Some had protruding foreheads, others had short, squashed faces. Some had enormous jaw muscles and big teeth, while others had enormous heads to hold bigger brains.

They had one thing in common, however: They were family -- our ancient family, that is, from around 2 million years ago.

The world's first completely preserved adult hominid skull from the early Pleistocene era looks surprisingly different from other skulls of the same era, yielding a remarkable insight: Man’s early ancestors appeared as physically diverse as humans do today, researchers said, and our family tree has perhaps fewer branches than today's schoolbooks teach.

“It’s a really extraordinary find,” said paleoanthropologist Marcia S. Ponce de Leon in a press conference Wednesday announcing the findings. “For the first time, we can see a population from the early Pleistocene. We only had individuals before. Now we can make comparisons and see the range of variation.”

'The five Dmanisi individuals are no more different from each other than any five modern humans or chimpanzees.'

— Neurobiologist Christoph Zollikofer from the Anthropological Institute and Museum in Zurich

The skull in question is a complete, 1.8-million-year-old ancestor of man, found in Dmanisi, Georgia, in Eastern Europe. The fifth such skull from the region spanning a period of a few centuries, it’s known at present only as “Skull 5” -- it hasn’t received a clever name yet like Lucy, the remarkable African skeleton found in the 70s and dating back 3.4 million years. (Lucy is an Australopithecus afarensis, an even more distant relative of modern man.)

The rarity of such artifacts makes studying them a challenge; other skulls from about 2 million years ago showed wide enough differences in shape that scientists have so far labeled them different species entirely: Homo habilis and Homo rudolfensis, for example.

Skull 5 is different, different even than the four other skulls found at Dmanisi. It was found in 2005, and ultimately matched to a jaw found in 2000 to make a complete skull. But after eight years of study, scientists on Thursday published a paper in the journal Science revealing that Skull 5 is simply not that different from others.

“The five Dmanisi individuals are no more different from each other than any five modern humans or chimpanzees,” said neurobiologist Christoph Zollikofer, a co-author of the paper with Ponce de Leon, both of whom work at the Anthropological Institute and Museum in Zurich, Switzerland.

“The brain case is very small -- around a third of [the size of] modern humans at 546 cubic centimeters -- and at the same time, we have the face that is quite large, and the jaws are quite massive, and the teeth are big and large,” she explained.

“This is a strange combination of features that we didn’t know before in early homo,” Ponce de Leon said. Such a skull shape was previously unseen, yet it was actually more similar to the others than it was different, the team found.

“Dmanisi is the first site where we can really look into and quantify variation in fossil hominid population,” Zollikofer said.

The site itself is an intriguing location that David Lordkipanidze from the Georgian National Museum Tbilisi, Georgia -- a third paper author -- described as “a medieval city on a hilltop.”

When these early hominids were walking around, 2 million years ago, the climate was temperate and relatively humid, he said. The site was a short distance from water, situated on the remants of a lava flow. Beyond just skulls, some scattered evidence of daily life remained too, as well as a wide variety of plant and animal remains spread over an area spanning about 1.2 acres.

“We found stone tools and cut marks on animal bones, which indicate that hominids were actively involved in meat-processing,” Lordkipanidze said. One of the skulls had a wound on its cheek too, which could have come from a fight following an argument or something as simple as an injury in a fall.

“This was a place with stiff competition between carnivores and hominids. We found almost a hundred carnivores and it seems they were fighting for the carcasses. Fortunately for the hominids -- and fortunately for us -- they were not always successful.”

But the real revelation is the variation among these ancient creatures, who had long legs and short arms and smaller brains than us. What other secrets does this mountain range hold?

"We still have a lot to discover,” he said.