After scientists dug out what could possibly be the oldest human fossil ever in Ethiopia, it was concluded that the origin of the Homo genus might be older by around half a million years than what has been previously thought.
The Homo mandible spotted in Ethiopia
The fossil of a lower jaw – “a partial hominin mandible with teeth” as described in the abstract of a scientific paper – that was discovered by scientists in the Ledi-Geraru research area, Afar Regional State, Ethiopia, back in 2013 has provided much insight into the origin of the human family.
The fossil, named LD 350-1, has also been described in another paper by another team of researchers. Both papers are available in the journal Science.
The dating of the fossil was done by examining the radioactive isotopes found in the layers of volcanic ash located above and below the fossil. From the dating results, the fossil was estimated to be about 2.8 million years old, making of it at least 400 000 years older than Homo fossils found in the past. The discovery has provided invaluable information as to fossil records from 2.5 to 3 million years ago.
“There is a big gap in the fossil record between about 2.5 million and 3 million years ago – there’s virtually nothing relating to the ancestors of Homo from that time period, in spite of a lot of people looking,” said one of the authors of the study, Brian Villmoare, from the University of Nevada. “Now we have a fossil of Homo from this time, the earliest evidence of Homo yet.”
The authors of the paper believe that the discovery will help situate the evolution of Homo both “geographically and temporally”.
The site where the fossil was excavated is located very near to the spot where the last known pieces of a hominid species believed to be the last ancestor of the Homo genus, the Australopithecus afarensis, were found. The latter originates from around 3.9 and 2.9 million years ago. Its most famous fossil was named Lucy.
The replica of Lucy in a museum in Mexico City
LD 350-1 and Lucy possibly have around 200 000 years separating them. The scientists believe that the new discovery will help piece together the line of ancestors of humans.
The species of the new jaw bone has, however, not been determined yet. It might be of a new species having remained unknown until now, or of an extinct human species like the Homo habilis.
Reconstruction of the Homo habilis at the Westfälisches Museum für Archäologie, Herne
Its morphology suggests that it might have been an intermediary, with characteristics of both a Homo species and a Australopithecus; its teeth cusp patters and proportions of the jaw resemble those of a Homo, while the chin is sloped like an Australopithecus.
The director of the Institute of Human Origins at Arizona State University, US, Bill Kimbel, described the physical features as follows:-
“This narrows the time period in which we can now focus our search for the emergence of the human lineage. It’s very much a transitional form, as would be expected at that age. The chin looks backwards in time. But the shape of the teeth looks forward.”
Co-author Villmoare also added that the findings revealed more questions than answers though:-
“These findings raise more questions than they answer. Hopefully these questions will be answered by further fieldwork.”