MIAMI // A piece of jawbone with teeth attached is the earliest known fossil of the genus – or biological subcategory – Homo, to which humans belong, a new study has revealed.
The discovery suggests that humankind’s ancestors were living in what is now the Ledi-Geraru research area of Ethiopia’s Afar Regional State in open grassland environments, near lakes, rivers, and active volcanoes, about 2.8 million years ago – 400,000 years earlier than previously thought.
“It is the first fossil we have on the [evolutionary] branch that leads toward us,” said Brian Villmoare, an assistant professor at the University of Nevada and lead author of the study in the journal Science.
The fossil – known as LD 350-1 – is the left side of a lower jawbone with five teeth, and was found in fine sediment near the surface of the research site in 2013.
It has not yet been assigned to a particular species, but the fossil’s slim molars and dental arch proportions indicate an advancement that is not seen in the more apelike Australopithecus afarensis, dating just a few hundred thousand years earlier.
The last known fossil of the most recent member of Australopithecus afarensis (“Lucy”) comes from the nearby Ethiopian site of Hadar and is about 3.2 million years old.
Meanwhile, the oldest known Homo fossil was – until now – believed to be about 2.3 or 2.4 million years old.
The refinement seen in the new fossil “suggests that the transition itself was relatively rapid,” Mr Villmoare said on Wednesday.
Experts described the fossil as a very early representative of the species that led to modern humans, though not a direct ancestor of our particular species, known as homo sapiens.
Researchers are particularly intrigued because the fossil dates to a period when few such artefacts have been found, and sheds light on the time when early hominids – members of the erect bipedal primate mammals family – diverged, as the ancestors of homo sapiens split from the more apelike australopithecus, which walked upright but had smaller brains.
“The fossil record in east Africa between two and three million years ago is very thin and there are relatively few fossils that can inform us about the origins of the genus homo,” said Mr Villmoare.
“However this is one of the most interesting periods in human evolution.”
* Agence France-Presse