NYU (US) — Fossils found in Kenya confirm three different human species living together at the dawn of humanity.
The finds, announced in the journal Nature, include a face, a complete lower jaw, and part of a second lower jaw. (See 360-degree videos of the fossils.)
The fossils were uncovered between 2007 and 2009 by the Koobi Fora Research Project (KFRP), led by paleontologists Meave and Louise Leakey. The products of a 40-year search, they provide the needed evidence to confirm that a disputed skull found in 1972 does in fact represent a new species, the team says.
KFRP’s fieldwork was facilitated by the Turkana Basin Institute (TBI), and supported by the National Geographic Society, which has funded the KFRP since 1968.
Susan Antón, a New York University anthropology professor and a member of the research team, was part of the effort to compare these fossils with those from earlier finds.
The new face KNM-ER 62000, as it was initially found, with some teeth just visible in the rock (left), and after the encasing rock was removed by Christopher Kiarie, revealing the palate (right). (Photos by Fred Spoor © NMK)
The left side of the lower jaw KNM-ER 60000, after preparation by Christopher Kiarie. (Photo by Fred Spoor © NMK)
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“These new fossils provide great tests of earlier hypotheses of how diverse the early Homo record was,” explains Antón. “They provide anatomical support for the idea of multiple species of early Homo, but, more importantly, they suggest ideas about how the species might have divided up the environment—these species weren’t separated into a large species and a small species; instead, the fossils suggest remarkable size variation within each species, but with different facial anatomies.”
Dated to between 1.78 and 1.95 million years ago, the remains were uncovered within six miles (ten kilometers) of the 1972 skull, which was discovered by Meave Leakey’s husband, paleoanthropologist Richard Leakey.
Known as KNM-ER 1470—”1470″ for short—the skull has “always been an enigma,” says Meave Leakey, a National Geographic Society explorer-in-residence.
“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,” says Meave Leakey. “At last we have some answers.”
“Combined, the three new fossils give a much clearer picture of what 1470 looked like,” says 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 face KNM-ER 62000, discovered by field crew member Elgite Lokorimudang in 2008, is very similar to that of 1470, showing that the latter is not a single “odd one out” individual. Moreover, the face’s well-preserved upper jaw has almost all of its cheek teeth still in place, which for the first time makes it possible to infer the type of lower jaw that would have fitted 1470.
A particularly good match can be found in the other two new fossils, the lower jaw KNM-ER 60000, found by Cyprian Nyete in 2009, and part of another lower jaw, KNM-ER 62003, found by Robert Moru in 2007. KNM-ER 60000 stands out as the most complete lower jaw of an early member of the genus Homo yet discovered.
Paleontologists Meave Leakey and Fred Spoor collect fossils close to the site where the new face KNM-ER 62000 was found. (© Photo by Mike Hettwer, www.hettwer.com , courtesy of National Geographic)
Fine sand and sediment passing through a screen at the site where KNM-ER 62000 was discovered. (© Photo by Mike Hettwer, www.hettwer.com , courtesy of National Geographic)
National Geographic Explorers-in-Residence Louise Leakey (left) and Meave Leakey search the slope where KNM-ER 60000 was discovered while, in the background, members of the field crew screen the surface sediment hoping to find additional fragments of this fossil. (© Photo by Mike Hettwer, www.hettwer.com, courtesy of National Geographic)
Food for three?
Another question is how the three early humans co-existed without stepping on each other’s toes. One possible clue emerging from the study is that 1470 and its kind were powerful chewers, according to a report by National Geographic News.
“The cheek bones are so far forward it means they would have been able to use quite a strong biting force,” Meave Leakey says.
With a chewing advantage, 1470 may have gravitated toward areas rich with nuts or tough fruits, or perhaps even meat, leaving the softer stuff to erectus and habilis. It could also be that these early human species just plain got along.
“Modern primates are generally very good at living together,” Leakey says. “You can see troops of monkeys composed of at least two species, if not more.”
The team working on the new finds included Christopher Kiarie of the Turkana Basin Institute (TBI), who carried out the laboratory preparation of the fossils, Rutgers University’s Craig Feibel, who studied the age of the fossils, as well as NYU’s Antón, University College London’s Christopher Dean, Meave and Louise Leakey of TBI, Kenya and Stony Brook University, and Fred Spoor of the Max Planck Institute for Evolutionary Anthropology, Leipzig and University College London, who analyzed the fossils.
The National Geographic Society funded the fieldwork, the Leakey Foundation funded geological studies, and the Max Planck Society supported laboratory work.
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