After analysing 1.9 million-year-old pelvis and thigh bones of an early human ancestor in Kenya, researchers have revealed greater diversity in the human family tree than scientists previously thought.
According to the team from University of Missouri-Columbia, apart from facial features, these early human species also differed throughout other parts of their skeletons and had distinct body forms.
"What these new fossils are telling us is that the early species of our genus, Homo, were more distinctive than we thought. They differed not only in their faces and jaws but in rest of their bodies too," said Carol Ward, professor of pathology and anatomical sciences.
The old depiction of linear evolution from ape to human with single steps in between is proving to be inaccurate.
"We are finding that evolution seemed to be experimenting with different human physical traits in different species before ending up with Homo sapiens," Ward noted.
These fossils show a diversity in the physical structures of human ancestors that has not been seen before.
"This new specimen has a hip joint like all other Homo species but it also has a thinner pelvis and thigh bone compared to Homo erectus," Ward added.
This does not necessarily mean that these early human ancestors moved or lived differently but it does suggest that they were a distinct species that could have been identified not just from looking at their faces and jaws, but by seeing their body shapes as well.
"Our new fossils, along with the other new specimens reported over the past few weeks, tell us that the evolution of our genus goes back much earlier than we thought, and that many species and types of early humans coexisted for about a million years before our ancestors became the only Homo species left," the authors wrote.
The study was published in the Journal of Human Evolution.
