New Human-Evolutionary Profile Found in 1.8-Million-Year-Old Fossil

Humans belonged to one species rather than a bunch of different ones, that is what a 1.8-million-year-old skull unearthed in the Republic of Georgia indicate.

The skull, known as Skull 5, is like nothing seen before. It was discovered in pieces in 2000 and 2005 alongside the remains of four other early human ancestors, a variety of animal fossils and some stone tools in the village of Dmanisi.

Those who have studied, published in Science, suggest that 1.8 million years ago humans belonged to one species rather than a bunch of different ones.

Los Angeles Times Teased:

In the humid foothills of the Caucasus Mountains, deep within a carnivore's bloody lair, an early human ancestor fought a life-or-death struggle, and lost.

He had entered the den on a scavenging mission, possibly with several others. Their plan: Use a stone to scrape meat from the bones of freshly killed prey, then flee before a saber-tooth cat or other giant predator caught him in the act.

"It seems that they were fighting for the carcasses, and unfortunately ... they were not always successful," said David Lordkipanidze, a paleoanthropologist and director of the Georgian National Museum in Tbilisi.

Now, nearly 2 million years later, the intact remains of that failed foraging mission are causing researchers to doubt the shape of the humanity's family tree.

What makes the find truly unique is that the skull and other remains provides a glimpse of a population of pre-humans of various sizes living at the same time and same geological space - something that scientists had not observed until now.

Scientists have studied the skull for eight years, comparing Skull 5's cranium and jaw with four other hominid skulls of individuals who died within a few centuries of each other at most.

By analyzing the shape of the Dmanisi skulls, they found that its measurements are similar to those found in modern humans.

The parallel suggests that all five Dmanisi individuals belonged to the same species of early human, which many scientists think spawned the lineage that led to us.

"Since we see a similar pattern and variation in the African fossil record ... it is sensible to assume that there was a single Homo species at that time in Africa," a co-author of the journal report, Christoph Zollikofer of the University of Zurich, said in a statement. "And since the Dmanisi hominids are so similar to the African ones, we further assume that they both represent the same species."

Skull 5 shares several characteristics from two early species, Homo habilis and Homo erectus, but the study's authors suggest that those along with a third early human species, Homo rudolfensis, are part of one species that stretched from Africa to Southeast Asia.

"We have, now, one global human species," Zollikofer told the Globe and Mail. "What we can infer from our studies at Dmanisi is that 1.8 million years ago, there was another single, global species."

While most scientists do find common ground in Skull 5's brain size, other scientists disagree. Paleoanthropologist Susan Antón of New York University told USA Today that the Dmanisi team did not compare the anatomy around the front teeth that differ between two different species of early humans. So she was not convinced by the team's hypothesis.