DMANISI, Georgia - The discovery of a 1.8-million-year-old skull of a human ancestor buried under a medieval Georgian village provides a vivid picture of early evolution and indicates our family tree may have fewer branches than some believe, scientists say.
The fossil is the most complete pre-human skull found. With other partial remains previously found at the rural site, it gives researchers the earliest evidence of human ancestors moving out of Africa and spreading north to the rest of the world, according to a study published Thursday in the journal Science.
The remains offer a glimpse of a population of pre-humans of various sizes living at the same time - something scientists hadn't seen before for such an ancient era.
Nearly all of the previous pre-human discoveries have been fragmented bones, scattered over time and locations - like a smattering of random tweets of our evolutionary history. The findings at Dmanisi are more complete, weaving more of a short story. Before the site was found, the movement from Africa was put at about 1 million years ago.
When examined with the earlier Georgian finds, the skull "shows that this special immigration out of Africa happened much earlier than we thought and a much more primitive group did it," said study lead author David Lordkipanidze, director of the Georgia National Museum. "This is important to understanding human evolution."
The skull wasn't from our species, Homo sapiens. It was from an ancestral species, in the same genus or class called Homo, that led to modern humans. Scientists say the Dmanisi population is likely an early part of our long-lived primary ancestral species, Homo erectus.
The skull was from an adult male just shy of 5 feet with a massive jaw and big teeth, but a small brain, implying limited thinking capability, said study co-author Marcia Ponce de Leon of the University of Zurich. It also seems to be the point where legs are getting longer, for walking upright, and hips smaller.
"This is a strange combination of features that we didn't know before in early Homo," Ponce de Leon said.