Brett Smith for redOrbit.com – Your Universe Online
As the human and primate fossil records become more complete, researchers are beginning to see the amount of complexity involved in man´s evolution.
That evolutionary tree became even more complex with the discovery of new fossils that suggest there were two additional Homo species living alongside our direct ancestors, Homo erectus, around two million years ago.
According to a report published in the journal Nature this week, the findings include a skeletal face, an unusually complete lower jaw, and part of a second lower jaw. All three were discovered between 2007 and 2009 near Lake Turkana in Kenya.
Researchers believe these new fossils are associated with a partial skull found 40 years ago by the Koobi Fora Research Project (KFRP), which was led by Meave and Louise Leakey and funded by National Geographic. The skull sparked a debate about just how many different species of early Homo lived alongside Homo erectus during the Pleistocene epoch.
Because this unique skull, dubbed 1470, did not include any teeth or lower jaw, the debate has persisted throughout the scientific community.
“For the past 40 years we have looked long and hard in the vast expanse of sediments around Lake Turkana for fossils that confirm the unique features of 1470’s face and show us what its teeth and lower jaw would have looked like,” said Meave Leakey, co-leader of the KFRP and a National Geographic Explorer-in-Residence. “At last we have some answers.”
“Combined, the three new fossils give a much clearer picture of what 1470 looked like,” said Fred Spoor, leader of the scientific analyses. “As a result, it is now clear that two species of early Homo lived alongside Homo erectus. The new fossils will greatly help in unraveling how our branch of human evolution first emerged and flourished almost two million years ago.”
The new specimens were discovered just over 6 miles from the location 1470 was found in 1972 and are dated between 1.8 million and 1.9 million years old. The fossils´ jaw structures, teeth, and other features suggest a link between them and 1470, although Spoor admitted they are not ready to categorically say “they were standing next to each other and could shake hands.”
Despite similarities to 1470, the scientists were also reluctant to officially classify the new finds as existing or brand new species of humanoid. In a companion piece printed in Nature, Bernard Wood of George Washington University suggested a path to determine how to classify these latest findings.
“So where do we go from here?” Wood asked. “More work needs to be done using the faces and lower jaws of modern humans and great apes to check how different the shapes and the palate can be among individuals in living species.”
He also noted that these findings have great significance and at the very least pointed to unknown details that could still muddy the waters of human evolutionary theory.
“In a nutshell, the anatomy of the specimens supports the hypothesis of multiple early Homo species,” Wood wrote, adding that, “researchers will view our current hypotheses about this phase of human evolution as remarkably simplistic.”