The Slatest

Human Origins Just Got a Lot Older




Close up view of the mandible just steps from where it was sighted by Chalachew Seyoum, an ASU graduate student from Ethiopia.




Courtesy of the journal Science  

One of the most important periods in human evolution—the origins of our lineage—has long been its least understood. But thanks to a discovery announced today in the journal Science, we know a little more.

A jawbone unearthed in Ethiopia in 2013 dates to approximately 2.8 million years ago and shares enough traits with fossils from the Homo genus—our branch of the family tree—for scientists to declare it the oldest human fossil ever found.

As Rachel Feltman explains at the Washington Post’s Speaking of Science blog, scientists have a fair amount of information about the genus Australopithecus, hominids that date from at least 4 million to 3 million years ago. For example, Lucy, one of the most important—and most famous—fossils ever discovered, is a member of Australopithecus afarensis species. Scientists also have a significant number of fossils documenting the Homo genus. But until now they did not know just how far back the genus might date.

The lower mandible, which scientists refer to lovingly as LD 350-1 and which includes the “partial or complete crowns and roots of the canine, both premolars, and all three molars,” was discovered in the Afar region (coincidentally, where Lucy was also discovered) and shares traits with both Australopithecus and Homo. This indicates that we might have evolved from Australopithecus rather than a different hominid family. “The researchers report that a sloping chin links the set of teeth to the ape-like Australopithecus, but narrow, symmetrical molars and jaw proportions place it clearly in the Homo genus,” Feltman writes.

Close up images of LD 350-1 mandible.

Courtesy of the journal Science

“Of course this specimen raises many more questions than it answers, and those questions will only be resolved by further field work,” said Brian Villmoare, one of the study’s leaders, in a news conference today.

In related paleontology news, another team of scientists did a virtual reconstruction of a fossil consisting of a partial skull and hand bones discovered by Louis Leakey’s son Johnny in the Olduvai Gorge in 1960 and categorized as Homo habilis. The remains were found in sediment that was 1.8 million years old, but the reconstruction, detailed in the journal Nature, gives a clearer picture of the lower jaw, allowing scientists to calculate that Homo habilis originated 2.3 million years ago.  

In a very short time frame, scientists have pushed back the age of Homo habilis and discovered an even older ancestor. Makes you feel old, doesn’t it?