Archaeologists have unearthed the 300,000-year-old fossilized bones of early humans — the oldest remains of Homo sapiens yet discovered, two new studies report. The ancient bones contain a mix of modern and primitive features that hint at an early, and previously unknown, phase of our species’ evolution.
On the family tree of human relatives, collectively known as hominins, our ancestors split from the Neanderthal branch more than 500,000 years ago. Fossils that looked like modern humans started showing up in East Africa about 200,000 years ago. But when exactly modern humans evolved from our most recent ancestor, probably Homo heidelbergensis, is a mystery. Now, two new studies published today in the journal Nature fill in some of those missing millennia, and suggest that hominins were well on their way to looking like modern day humans about 300,000 years ago.
The fossils come from an archaeological site in Morocco, called Jebel Irhoud. Hominin bones were first pulled out of the ground there in the 1960s, and were dated to about 40,000 years ago. But the archaeologists were sloppy, and experts began to suspect that date was very wrong. So, in 2004, the site reopened and over the next seven years, archaeologists unearthed more hominin remains, including parts of skulls and jaw bones. They also found animal bones that had been butchered and possibly cooked, and stone tools that had been burned at some point — all in the same layer of dirt. That’s key: being in the same layer means these finds were all approximately the same age.
The stone tools were a lucky find, because they gave the researchers — led by Jean-Jacques Hublin and Shannon McPherron at the Max Planck Institute in Germany — a chance to date that layer precisely. By measuring how many electrons accumulated in the tools over millennia, the researchers dated the layer and the hominin bones within it to about 315,000 years ago.
From the skull fragments, the researchers virtually reconstructed the faces of the ancient humans who had once lived at the site. Their features were small, and their faces were tucked underneath the brain case, rather than jutting out in front. “The face is the face of somebody you could cross in the metro,” Hublin told Michael Greshko in National Geographic. But the brain case was more primitive — flatter and longer instead of high and round, like ours. That’s why Hublin and his colleagues think the ancient denizens of Jebel Irhoud were an early evolutionary phase of Homo sapiens — somewhere on the developmental path between Homo heidelbergensisand us.
The two authors of an analysis published alongside the study agree with this assessment. But, the findings haven’t been met with universal approval. Paleoanthropologist John Hawks at the University of Wisconsin-Madison told Greshko that these new studies “really aren’t adding anything new except the date.” Hawks added that he doesn’t think the findings warrant creating a new category of “early modern humans” to describe the mix of primitive and modern traits. But, regardless of what we call these ancient relatives of ours, these new findings give us a better idea of how we became who we are today.
Published at Wed, 07 Jun 2017 22:49:06 +0000