Revisiting a Renowned Skull From Early Human Homo Erectus

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Two scientists in the field examine a specimen together. University of Witwatersrand geologist Silindokuhle Mavuso (left) and study lead author Ashley Hammond (right) at the East Turkana site in Kenya.
A. Hammond/© AMNH

Nearly 50 years ago, scientists working in East Turkana in northern Kenya found a small skull fragment that became one of oldest pieces of evidence for Homo erectus, a very successful early human who roamed the world for nearly 2 million years. But some paleoanthropologists expressed skepticism about the age of the skull fragment—1.9 million years—arguing that it could have come from a younger fossil deposit, possibly moved  to the spot where it was found by water or wind.

Now, a new study led by Museum Assistant Curator Ashley Hammond cements the age and origin of this renowned specimen and describes two new fossils found at the site. The specimens may be the earliest pieces of the Homo erectus skeleton yet discovered. Details are published today in the journal Nature Communications.

Homo erectus is the first hominin that we know about that has a body plan more like our own and seemed to be on its way to being more human-like,” said Hammond, a paleoanthropologist in the Museum’s Division of Anthropology. “It had longer lower limbs than upper limbs, a torso shaped more like ours, a larger cranial capacity than earlier hominins, and is associated with a tool industry—it’s a faster, smarter hominin than Australopithecus and earliest Homo.”

When the East Turkana skull specimen was found in 1974—well before fossil finds could be documented with GPS—limited notes and photos were taken. So Dr. Hammond and her team launched geological detective work, sifting through hundreds of pages from old reports and published research and combining those “clues” with satellite data and aerial imagery to pinpoint the locality.

They did not find any evidence of a younger fossil outcrop that may have washed into the area where the skull specimen was found, supporting the original age given to the fossil. 

At the same time, fieldwork assisted by students and staff from the Koobi Fora Field School led to the discovery of two new hominin specimens within 50 meters of the reconstructed location. The specimens, a partial pelvis and a foot bone, potentially are H. erectus. They could be from the same individual, but there is no way to prove that after the fossils have been separated for so long. Still, they might be the earliest postcrania—“below the head”—specimens yet discovered for H. erectus.

Fingers holding an identification label above a partial pelvis.
One of two new hominin specimens, a partial pelvis, found at the East Turkana site in Kenya.
A. Hammond/© AMNH

“This kind of renewed collaboration not only sheds new light on verifying the age and origin of Homo erectus but also promotes the National Museums of Kenya’s heritage stewardship in research and training,” said Emmanuel Ndiema, the head of archaeology at the National Museums of Kenya, which co-directs the Koobi Fora Field School.  

The researchers also collected fossilized teeth from other kinds of vertebrates, mostly mammals, from the area. From the enamel, the team analyzed isotope data to paint a better picture of the environment in which the H. erectus individual lived. The work suggests that this early H. erectus was found in a paleoenvironment that included primarily grazers that prefer open environments to forest areas and was near a stable body of water.