Pelvis discovery adds variety to human body types

"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," says Carol Ward. (Credit: University of Missouri)

An analysis of pelvis and femur fossils suggest early humans not only had different facial features, but also different body types.

The fossils found in Kenya are from an early human ancestor who lived 1.9 million years ago.

“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 the rest of their bodies too,” says Carol Ward, professor of pathology and anatomical sciences at University of Missouri.

3 early species

“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.”

Three early species belonging to the genus Homo have been identified prior to modern humans, or Homo sapiens: Homo rudolfensis and Homo habilis were the earliest versions, followed by Homo erectus and then Homo sapiens.

Because the oldest erectus fossils that have been found are only 1.8 million years old, and have different bone structure than the new fossil, Ward and colleagues conclude the fossils they have discovered are either rudolfensis or habilis. These fossils show a diversity in the physical structures of human ancestors that has not been seen before.

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“This new specimen has a hip joint like all other Homo species, but it also has a thinner pelvis and thighbone compared to Homo erectus,” Ward says. “This doesn’t 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.”

A small piece of the fossil femur was first discovered in 1980 at the Koobi Fora site in Kenya. Project co-investigator Meave Leakey returned to the site with her team in 2009 and uncovered the rest of the same femur and matching pelvis, proving that both fossils belonged to the same individual 1.9 million years ago.

Researchers from Stony Brook University, Rutgers, University of Arkansas, the Max Planck Institute for Evolutionary Anthropology, and University College London are coauthors of the study. The fossils are housed at the National Museums of Kenya.

The study was published in the Journal of Human Evolution.

Source: University of Missouri