August 9, 2012 (TSR) – Exciting new fossils discovered east of Lake Turkana confirm that there were two additional species of our genus – Homo – living alongside our direct human ancestral species, Homo erectus, almost two million years ago.
The finds, announced in the prestigious scientific journal Nature on August 9th, include a face, a remarkably complete lower jaw, and part of a second lower jaw. They were uncovered between 2007 and 2009 by the Koobi Fora Research Project (KFRP), led by Meave and Louise Leakey.
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.
VIDEO: Students search for fossils at beautiful Lake Turkana, Kenya.
Four decades ago, the KFRP discovered the enigmatic fossil known as KNM-ER 1470 (or “1470” for short). This skull, readily distinguished by its large brain size and long flat face, ignited a longstanding debate about just how many different species of early Homo lived alongside Homo erectus during the Pleistocene epoch. 1470’s unusual morphology was attributed by some scientists to sexual differences and natural degrees of variation within a single species, whereas others interpreted the fossil as evidence of a separate species.
This decades-old dilemma has endured for two reasons. First, comparisons with other fossils have been limited due to the fact that 1470’s remains do not include its teeth or lower jaw. Second, no other fossil skull has mirrored 1470’s flat and long face, leaving in doubt just how representative these characteristics are. The new fossils address both issues.
“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, 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,” 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.”
Found within a radius of just over 10 km from 1470’s location, the three new fossils are dated between 1.78 million and 1.95 million years old.
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.
KNM:ER 62000 VIDEO: Just over 10 km from the location of KNM-ER 1470’s discovery, this specimen was discovered by Daniel Elgitei, encased in a block of sandstone. Remarkably, he spotted the two shiny black teeth, which were the only indication that there was a fossil hidden in the rock. Back in the preparatory lab the rock was later removed with an airscrbe and this beautifully preserved fossil emerged. It has distinctive forwardly placed cheek bones and a very flat profile to its face. The face belonged to a juvenile or subadult Homo rudolfensis, and closely resembles the face of KNM-ER 1470, although it is notably smaller in size. The large size difference indicates that the males and females of this species differed in their body size, or were “sexually dimorphic”. There are several teeth preserved and the shape of the palate of this fossil is similar to the dental arcade of the new mandible KNM-ER 60000.
KNM-ER 620003 VIDEO: This is a piece of mandible belonging to an adult or late sub-adult individual of Homo rudolfensis. The fragment of the right side of the mandible, extends from the midline and preserves some of the roots and the molar crowns of three of the teeth. This specimen was discovered by Robert Moru, in July in 2007, while with other members of the Koobi Fora Reserch Project, he was exploring Area 130 on the east side of Lake Turkana. It complements the newly described complete mandible, and adds to the very small sample of specimens that can be confidently attributed to the species Homo rudolfensis.
KNM-ER 6000 RECONSTRUCTION
KNM-ER 6000 VIDEO: This is a nearly complete lower jaw with a full set of teeth. Its characteristic small front teeth (incisors) and flat profile across the incisors is consistent with the shape of the newly published specimen KNM-ER 62000 and skull KNM-ER 1470. This mandible was spotted by Cyprian Nyete, who was clambering over a very steep hillside, in his search for fossils. Looking up he spotted a fragment of a fossil close to the top of the slope. The rest of this specimen had washed down a small gully and had been covered with silt and rocks. All the missing pieces were slowly recovered by screening all the surface rocks and sands and excavating areas where it seemed possible more of the fossil might be buried under the surface. There was just a slim chance, with such a complete lower jaw preserved, the skull of this individual might have been nearby. But this did not turn up.
The team working on the new finds included Christopher Kiarie (TBI), who carried out the laboratory preparation of the fossils, Craig Feibel (Rutgers University), who studied the age of the fossils, and Susan Antón (New York University), Christopher Dean (UCL, University College London), Meave and Louise Leakey (TBI, Kenya; and Stony Brook University, New York) and Fred Spoor (Max Planck Institute for Evolutionary Anthropology, Leipzig and UCL), who analysed the fossils.
The National Geographic Society funded the fieldwork, the Leakey Foundation funded geological studies, and the Max Planck Society supported laboratory work.
TBI is a privately funded, non-profit initiative founded by Richard Leakey and Stony Brook University, New York, that seeks to facilitate multi-disciplinary fieldwork within the Lake Turkana Basin in affiliation with the National Museums of Kenya. The primary research focus is human prehistory and related earth and natural science studies.
Source: Stony Brook University, New York