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Author Topic: 'Lucy's baby' found  (Read 592 times)
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« on: September 20, 2006, 06:49:44 PM »

The juvenile specimen is wonderfully preserved.  ? Nature

Three-million-year-old child unearthed

A three-million-year-old skeleton of a three-year-old child has been uncovered in Dikika in Ethiopia.

The child, probably female, belongs to Australopithecus afarensis , an ancient pre-human species that lived around three to four million years ago and includes the famous 'Lucy' skeleton found in Ethiopia in 1974.  However, this new fossil is actually about 200,000 years older than Lucy.

The skeleton is remarkably complete for such an ancient pre-human specimen. It includes a well-preserved face, brain case, lower jaw and all but two of the teeth, including unerupted teeth still in the jaw.

'This is a very special find,' said Chris Stringer, human evolution expert at the Natural History Museum.  'It's not until we come to intentional burials by Neanderthals and modern humans in the last 100,000 years that we otherwise find such well-preserved infant remains, because of their fragility.'

The specimen reveals the child had many morphological similarities to African apes such as in the hyoid bone found in the throat. This is the first time a hyoid bone has been found from this time period. Clues from her feet and lower limbs show evidence for walking upright but her gorilla-like scapula and long and curved phalanges or finger bones suggest that she also climed trees.

Chris adds, 'The new fossil reinforces the view that the australopithecines (southern apes) were human-like in the lower part of the body (hips, legs, feet) but still rather ape-like in the upper part (shoulder, arms, hands), walking on two legs when on the ground, but retaining the ability to climb in the trees.'
Buried intact

The infant was found in sediments at the bottom of a slow-flowing channel between a river and a lake. The slow flow of water allowed the body to be buried intact and the sediment flowing in the water would have quickly covered it up, helping to preserve her so well.

Zeresenay Alemseged, from the Max-Planck Institute for Evolutionary Anthropology in Germany, spent thousands of hours carefully removing the hard sandstone that encased the skeleton.
Possible ancient human ancestor

A. afarensis was a possible ancient human ancestor that lived three to four million years ago. This species existed at an important time in human evolution sharing similarities with both apes and humans.

'This infant australopithecine is a very valuable addition to the hominin fossil record,' said Louise Humphrey, human evolution expert at the Natural History Museum.

'The skeleton is exceptionally well preserved and promises to reveal an enormous amount of information about the lifestyle of this young australopithecine.'

'The skeleton and dentition can provide remarkable insights into how australopithecines developed and advance our understanding of when modern human growth and life history patterns evolved.'

This research is reported in the journal  Nature .

Australopithecus afarensis

Picture of Lucy Remains, Museo Nacional de Antropolog?a, Mexico City

Australopithecus afarensis is a hominid which lived between 3.9 to 3 million years ago. In common with the younger Australopithecus africanus, A. africanus was slenderly built, or gracile. It is widely believed that A. afarensis is the ancestor of the genus Homo, which includes our own species, Homo sapiens.

Type Specimen
The Type Specimen for A. afarensis is L.H. 4, an adult mandible from the site of Laetoli, Tanzania.

Australopithecus afarensis fossils have only been discovered within Eastern Africa. Despite Laetoli being the type locality for A. afarensis, the most extensive remains assigned to this species are found in Hadar, Ethiopia, including the famous "Lucy" partial skeleton and the "First Family" found at the A.L. 333 locality. Other localities bearing A. afarensis remains include Omo, Maka, Fejej and Belohdelie in Ethiopia, and Koobi Fora and Lothagam in Kenya.

The first A. afarensis skeleton was discovered on November 24, 1974 by Donald Johanson, Maurice Taieb, Yves Coppens and Tim White in the Middle Awash of Ethiopia's Afar Depression.

Physical characteristics

Chimp-sized brain

One of the most striking characteristics possessed by Lucy and other Australopithecines was that they had a relatively small brain and prognathic (i.e. projecting anteriorly) face, despite having some more advanced features, such as reduced canines and molars, and a hip and knee associated with bipedalism. The image of a bipedal hominid with small skull, but teeth like a human, was quite a revelation to the paleoanthropological world at the time.

This was due to the earlier belief (1950-1970's) that increasing brain size of apes was the trigger for evolving towards humans. Before Lucy, a fossil called 'KNM-ER 1470' (Homo rudolfensis) with a brain capacity of about 800 cubic centimetres had been discovered, an ape with a bigger brain. If the older theory was correct, humans most likely evolved from the latter. However, it turned out Lucy was the older fossil, yet Lucy was bipedal (walked upright) and had a brain of only around 375 to 500 cc. These facts provided a basis to challenge the older views.


How A. afarensis moved is controversial. Some believe that A. afarensis were habitual bipeds, while others believe that the creatures were partly arboreal. The anatomy of the hands and feet favour the latter interpretation. The curved fingers on A. afarensis are similar to those of modern-day apes, and is reflective of their ability to climb trees. The phalanges (finger bones) aren't just prone to bend at the joints, but rather the bones themselves are curved.

Another aspect of the Australopithecus skeleton that differs from human skeleton is the iliac crest of the pelvic bones. The iliac crest, or hip bone, on a Homo sapiens extends front-to-back, allowing an aligned gait. A human walks with one foot in front of the other. However, on Australopithecus and on other ape and ape-like species such as the orangutan, the iliac crest extends laterally (out to the side), causing the legs to stick out to the side, not straight forward. This gives a side-to-side rocking motion as the animal walks, not a forward gait.

There are several theories on how A. afarensis began bipedalism. The so-called 'savanna theory' on how A. afarensis evolved bipedalism hangs on the evidence that around 6 to 8 million years ago there seems to have been a mass extinction of forest dwelling creatures including the oldest hominins recognizable: Sahelanthropus tchadensis and Orrorin tugenensis. This triggered a burst of adaptive radiation, an evolutionary characteristic that generates new species quickly. Lucy's genetic forebears were tree dwelling apes, but in Lucy's world the trees would have been much fewer, and Lucy would have been forced to find a living on the flat savanna. Being bipedal would have had evolutionary advantages. For example, with the eyes higher up, she could see further than quadrupeds. Bipedalism also saves energy. The disadvantages of bipedalism were great?Lucy was the slowest moving primate of her time, for example, but according to the hypothesis, the advantages of bipedalism must have outweighed the disadvantages.

The so-called aquatic ape theory compares the typical elements of human locomotion (truncal erectness, aligned body, two-leggedness, striding gait, very long legs, valgus knees, plantigrady etc.) with those of chimpanzees and other animals, and proposes that human ancestors evolved from vertical wader-climbers in coastal or swamp forests to shoreline dwellers who collected coconuts, turtles, bird eggs, shellfish etc. by beach-combing, wading and diving. In this view, the australopithecines largely conserved the ancestral vertical wading-climbing locomotion in swamp forests ("gracile" kind, including Australopithecus afarensis and A. africanus) and later more open wetlands ("robust" kind, including Paranthropus boisei and P. robustus). Meanwhile, Plio-Pleistocene Homo had dispersed along the African Rift valley lakes and African and Indian ocean coasts, from where different Homo populations ventured inland along rivers and lakes. However, this theory is not taken seriously by anthropologists.

Social characteristics

These hominins were likely to have exhibited a to be somewhat like modern Homo sapiens when it came to the matter of social behavior, yet like modern day apes they relied on the safety of trees from predators such as lions.

Social structures of modern apes and monkeys can be anticipated to some extent by the average body size, the range of body size, and habitat. If this is applied to A. afarensis then these creatures were most likely to have lived in groups containing a single male and a number of females.

There are no known stone-tools associated with A. afarensis, and the present archeological record of stone artifacts only dates back to approximately 2.5 Ma.

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« Reply #1 on: October 04, 2006, 11:56:58 AM »

Anthropologist challenges species identification of ancient child skeleton found in Ethiopia

Pitt's Jeffrey Schwartz, who with colleague Ian Tattersall compiled the entire human fossil record, says specimen is not from Ethiopia and classification is premature.

   According to University of Pittsburgh anthropology professor Jeffrey Schwartz, author of the four-volume The Human Fossil Record (Wiley-Liss, 2002-05), "the discovery of any largely complete skeleton of an ancient human relative would be unique. The fact that it is a child makes it even more exciting because of what its bones and teeth might reveal that an adult's cannot."

   However, Schwartz said, there are questions about the species this specimen represents. He explained that the problem is that "Lucy" and this child specimen from Dikika have been placed in Australopithecus afarensis, which is not from Ethiopia but from Laetoli, a site in Tanzania thousands of kilometers to the south. But while other specimens from Laetoli are similar to this specimen, defined as A. afarensis, a recent study of virtually all the fossils from Lucy's region of Hadar by Schwartz and Ian Tattersall, curator of anthropology at the American Museum of Natural History in New York, has revealed that none is similar in detail to the fossils from Laetoli.

   "This means, of course, that no Hadar specimen is A. afarensis," said Schwartz, a fellow of the prestigious World Academy of Arts and Science.

   Just as Donald Johanson, discoverer of the 3.2 million-year old Lucy, initially suggested, Schwartz and Tattersall found there is more than one kind of hominid represented in the Hadar material.

   "Since the chewing surfaces of the Dikika child's teeth have not yet been exposed, one cannot compare it with any of the Hadar specimens or with the type specimen of A. afarensis from Laetoli," Schwarz explained. "Until this can be done, one cannot tell whether the Dikika child really is the first specimen of Ethiopian A. afarensis or, if not, whether it compares favorably with one of the hominids from Hadar or it represents a different taxon altogether."

     Schwartz and Tattersall's The Human Fossil Record represents the first study of the entire human fossil record. Volume 1 was recognized by the Association of American Publishers with its Professional Scholarly Publishing Award.


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« Reply #2 on: October 04, 2006, 12:13:23 PM »

Looks like it's back to the drawing board!

I did wonder, just by looking at the skeleton. My own view is that this subject contains a large element of speculation. For example, is there sufficient number of cases to allow broad conclusion to be drawn? Do we understand DNA sufficiently well to make relationships across such long periods of time? The fact that most bones come from a few areas, which is probably due to the climate there preserving them, maybe skews the results?

Remember all the jokes about the 'missing link'? Looking for the link between us and earlier primates? Seems to me that the creatures being discussed here more primitive primate - ape, chimp, whatever - than human. Personally, I doubt the claims made for them: I think science has a long way to go yet.

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« Reply #3 on: October 04, 2006, 07:08:38 PM »

Everyone likes to think their work is very important, it is what keeps us going. While I am no expert in this , but I have  seen most of what is out there. It sure looks like a chimp skull to me. And the skeletal frame is misssing just enough to allow one to view and reconstruct it to suit their whim. agreed, we have a long way to go.

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« Reply #4 on: October 05, 2006, 08:49:42 AM »

Bart: I'm sure this work is important, but not so sure that the headlines surrounding it contain much of importance.

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« Reply #5 on: April 01, 2007, 07:32:25 PM »

Human ancestor gets digital facelift

By Ker Than - Staff Writer
March 30, 2007

Reconstruction suggests large brains did not appear until much later

    The left image shows the original reconstruction of KNM-ER 1470, a 1.9 million-year-old early human skull discovered in Kenya. On the right is Timothy Bromage?s computer-simulated reconstruction, which shows the same skull with a distinctly protruding jaw. The green and red lines mark the location of the eyes, ears, and mouth, which must be in precise relationship to one another in all mammals.

   An ancient member of the human family has gotten a digital facelift, and the new mug looks more ape-like than scientists previously thought.

   The new reconstruction suggests the large brains and flatter faces characteristic of modern humans did not appear in our lineage until much later in our history.

   ?For how many years now, people have been using this [skull] and the numbers may not be very meaningful,? said Timothy Bromage, an anthropologist at New York University who led the new reconstruction effort.

   The skull in question, KNM-ER 1470, is arguably the most controversial fossil in the history of anthropology.

   When it was first discovered in northern Kenya in 1972, it was initially dated to nearly 3 million years old. Yet the skull ? which scientists painstakingly pieced together from hundreds of bone fragments ? had a large brain and a flat face, features reminiscent of modern humans but completely unlike any hominid known to exist at the time.

   So troublesome was the skull that famed paleo-anthropologist Richard Leakey, the leader of the team that discovered it, once told reporters: "Either we toss out this skull or we toss out our theories of early man. It simply fits no models of human beginnings."

   Leakey later revised the age of KNM-ER 1470 to 1.9 million years, but even then, some scientists have argued that the skull?s features are much more humanlike than its contemporary, Homo habilis.
Other scientists claim Homo rudolfensis, the name that some anthropologists have assigned to the skull, should be identified as a H. habilis and not a separate species at all. Whether either of these hominids was a direct ancestor of humans is still an open question.

Impossible face

   For the new reconstruction, the researchers used a combination of a deformable cast and computer-generated models to create replicas of KNM-ER 1470?s skull that could be shaped.

   Bromage said the original reconstruction relied on preconceptions about how early humans looked that are now known to be incorrect. The result, he said, was a skull that shared several features in common with modern humans, including a relatively flat face and a large brain case.

   ?It?s always been an outlier in every study ever performed on [hominid] brain sizes? from that period, Bromage said.

   Bromage said his team?s reconstruction includes biological principles not known at the time of the skull?s discovery, which state that a mammal?s eyes, ears and mouth must be in precise relationships relative to one another.

   ?It doesn?t matter if you?re a rat, a kangaroo, an elephant, a human or a dog?their [facial features] are all organized to a very specific architectural plan,? Bromage said.

   For example, Bromage said, take any mammal and draw an imaginary line from the last permanent molar in its jaw that extends towards the opening of the ear and out the center of the eye socket. The angle of that line should be around 45 degrees.

   ?What this does is distribute the senses in a very specific way,? Bromage explained.

   In the original KNM-ER 1470 reconstruction, this angle was between 60 and 75 degrees, Bromage said. ?It was absolutely incompatible with life,? he said. ?The jaw would have been positioned so far back in the skull that there would have been no room for an airway or esophagus. It couldn?t breathe or eat.?

   Bromage presented his team?s findings at the annual meeting of the International Association for Dental Research last week and is submitting the results to a scientific journal for peer review later this year.

Smaller brain too?

   The new reconstruction suggests H. rudolfensis? jaw jutted out much farther than previously thought. The researchers say the cranial capacity of a hominid can be estimated based on the angle of the jaw?s slope and they have downsized KNM-ER 1470?s cranial capacity from 752 cubic centimeters to about 526 cc. (Humans have an average cranial capacity of about 1,300 cc.)

   But not everyone agrees that brain size can be inferred from jaw protrusion. Biological anthropologist Robert Martin, of the Field Museum in Chicago, said the researchers ?may well be right? in their reconstruction of the face, but said the researchers? claims about being able to estimate cranial capacity from facial features are ?crazy.?

   ?What they?re claiming is you stick the face out, and because the face sticks out more the brain capacity has to be less. I don?t follow that at all,? said Martin, who is an expert on hominid skulls and who was not involved in the study.

   ?They haven?t changed the skull at all; they?ve simply rotated the face outwards,? Martin added.
Martin also disputes the claim that H. rudolfensis? large cranial capacity made it stand out among ancient hominids. Martin points out that a 1.6 million-year-old Homo erectus skeleton known as ?Turkana Boy? had a cranial capacity of about 900 cc.

   ?At 1.9, you?ve got [H. rudolfensis] with [a cranial capacity] of 750 cc, and at 1.6 you?ve got 900 cc. I don?t have a problem with that,? Martin said.

   If confirmed, KNM-ER1470?s new cranial capacity would be comparable to that of H. habilis. ?Now it?s no longer an outlier,? Bromage said. ?It?s just part of the gang.?

   It would also suggest humans developed their characteristically large brains and flatter faces at least 300,000 years later than previously thought, perhaps as recently as 1.6 to one million years ago when H. erectus and another later hominid, Homo ergaster, lived.


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« Reply #6 on: July 12, 2007, 08:56:13 AM »

Researchers have found fossil remains of early human ancestors in Ethiopia that date to a little known period in human evolution.

The cache included several complete jaws and one partial skeleton, and was unearthed at Woranso-Mille in the country's Afar desert.

The remains were recovered 30km from the site where "Lucy" - one of the most famous human ancestors - was found.

New Discoveries from the Afar Fill a Major Gap in the Early Hominid Fossil Record

Cleveland, Ohio � Scientists working in the Woranso-Mille area of the Afar Region, Ethiopia, have recovered fossils that may prove to be a bridge to establishing a relationship between the earlier Australopithecus anamensis (4.2 - 3.9 million years) and the later Australopithecus afarensis (3 - 3.6 million years) early human species.

Researchers have hypothesized an ancestor-descendant relationship between these two species based on their similarities. However, until now, there has been no hominid fossil record from the 3.6 - 3.9 million years time frame to determine this relationship.  According to project co-leader Dr. Yohannes Haile-Selassie, curator and head of physical anthropology at The Cleveland Museum of Natural History, his team�s 2007 field season in the Woranso-Mille study area was unusually successful and uncovered key physical evidence.

�We recovered fossil hominids that date to between 3.5 and 3.8 million years ago,� said Haile-Selassie.  �These specimens sample the right time to look into the relationship between Australopithecus anamensis and Australopithecus afarensis and will play a major role in testing the ancestor-descendant hypothesis.�  The project team found isolated teeth from this time frame during its earlier field seasons.  However, during the 2007 field season, they recovered more complete jaws that are important to conduct comparative analysis.

At least 40 hominid specimens have been recovered thus far, including a number of complete jaws found in 2007, and a partial skeleton found in 2005.  These join the more than 1,900 vertebrate fossil specimens discovered in four consecutive field seasons in the Woranso-Mille area.  A total of more than 35 mammalian species in more than 20 genera have been sampled to date.


The Afar Depression of Ethiopia has yielded early hominid fossil remains spanning the last 6 million years. This has placed Ethiopia in the forefront of paleoanthropology, the study of human physical and cultural evolution. Ethiopia is known to the world as the cradle of humankind, with a minimum of 12 early human species known from the country, including the earliest hominid Ardipithecus kadabba at 5.8 million years ago, and Homo sapiens idaltu, the earliest anatomically modern human at 160,000 years ago.  For the last four decades, numerous local and foreign scientists have carried out fieldwork in the Afar region, searching for fossil remains of the earliest human ancestors.  Major areas that have been extensively explored, and have yielded early hominid fossil remains include Hadar, Middle Awash, Gona, and Dikika, all located in the Afar Regional State. The Afar region still has unexplored areas of paleoanthropological interest. As a result, new exploratory programs are being developed and new paleontological sites identified.

The Woranso-Mille project, led by Drs. Yohannes Haile-Selassie and Bruce Latimer of The Cleveland Museum of Natural History, Cleveland, Ohio, United States, has been conducting its paleoanthropological research in the central Afar area since 2003.  This area was identified as a result of survey and exploration conducted in 2002.  The Woranso-Mille Project is a multinational and multidisciplinary project and has thus far conducted four consecutive field seasons within the Mille-Chifra-Kasagita Triangle. Members of the project include scientists from The Cleveland Museum of Natural History, the Addis Ababa University, Case Western Reserve University, and Berkeley Geochronology Center.

The Site

The Woranso-Mille paleontological site is located in the central Afar area in the Mille and Chifra districts of Zone 1 of the Afar Regional State.  The study area is defined by the towns of Mille, Chifra, and Kasagita.  In this study area, a total of 29 vertebrate localities have been designated thus far. Major fossiliferous areas are divided into propers, with a number of localities designated within each proper.  The Aralee Issie, Mesgid Dora, and Makah Mera propers are located on the north side of the Mille River, and comprise a total of 11 designated localities.  Additional localities on the north side of the Mille River are Godaya, Harabi, Am-Ado, and Lehaytu Gera.  On the south side of the Mille River, major fossiliferous localities are designated in the areas locally known as Korsi Dora, Burtele, Nefuraytu, Leado Dodo'a, and Leadu.

The Fossil Discoveries

A total of 1,900 vertebrate fossil remains have been collected from the study area since 2003.  Project leader Haile-Selassie states that these fossils represent diverse animals ranging from small mammals, such as mice, to large ones, such as elephants.  Carnivores, monkeys, and bovids, are among the most abundant groups. However, other taxa, such as primitive horses, rhinoceros, hippopotamus, crocodile, and fish are also present. A total of more than 35 mammalian species in more than 20 genera have been sampled to date.  The total number of fossil remains of early hominids discovered from the site is relatively small, as in other hominid-bearing sites in Ethiopia and elsewhere. However, at least 40 hominid specimens have been recovered thus far, including a number of complete jaws and one partial skeleton, which was found in 2005. The excavation of this partial skeleton is still under way.

Age of the Fossils

Preliminary radiometric dates for some volcanic layers in the study area, bracketing most of the fossiliferous horizons, range from 3.5 to 3.8 Ma.  Project Geochronologist Dr. Alan Deino explains that these dates are based on single-crystal dating of K-feldspar bearing tuffs found within the stratigraphic succession and incremental heating of samples of basaltic lava. These preliminary radiometric dates agree well with biostratigraphic age estimates of 3.6 to 3.8 Ma.  This shows that the Woranso-Mille succession is much older than Hadar, where the oldest deposits are 3.4 million years old. Hadar is renowned in the field of paleoanthropology, as most of the Australopithecus afarensis (Lucy's species) fossil specimens were discovered there.   Woranso-Mille localities are slightly younger than the 4 million year old Asa Issie (Middle Awash), where remains of Australopithecus anamensis have been recently described by the Middle Awash project. The Woranso-Mille study area has some of the few (probably the best) known hominid-bearing exposures sampling the time between 3.5 and 3.9 million years ago.  The area also samples vertebrate fossils from horizons that are younger and older than this time range, extending into the late Miocene.

Significance of the hominid fossils

The fossil hominids from the Woranso-Mille area sample a time period that is poorly known in human evolutionary studies. An outstanding question in the study of early human evolution, says Haile-Selassie, relates to the relationship between the earlier Australopithecus anamensis (4.2 - 3.9 million years) and the later Australopithecus afarensis (3 - 3.6 million years).  Researchers have hypothesized an ancestor-descendant relationship between these two species based on their similarities.  However, there has been no fossil record from the 3.6 - 3.9 million years time frame thus far to test, confirm, or falsify this relationship.  Haile-Selassie adds that the fossil hominids from the Woranso-Mille study area dated to between 3.5 and 3.8 million years ago sample the right time and play a major role in testing the hypothesis with fossil data.  The Woranso-Mille fossil hominids from the deposits younger than 3.5 million years extend the geographic distribution of Australopithecus afarensis further to the north of Hadar, where the species is best documented.

Future Prospects

The paleontological significance of the Woranso-Mille study area has been demonstrated by the discovery of more than 1,900 vertebrate fossil specimens in three years of fieldwork.  These fossils include a number of hominid remains from different time horizons.  However, the study area has not been fully explored. Preliminary survey in some areas shows that there are fossiliferous deposits as old as 5 million years ago.  However, the project has not yet intensively concentrated on these areas.  During the coming field seasons, the Woranso-Mille project plans to systematically collect more fossils from already designated vertebrate localities and to find new areas with fossils of older age.

Contact Information

For further information, contact Dr. Yohannes Haile-Selassie at , or
tel. (011) 251-91-167-7796.

The Cleveland Museum of Natural History, incorporated in 1920, is one of the finest institutions
of its kind in North America. It is noted for its collections, research, educational programs and
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« Reply #7 on: August 09, 2007, 11:21:39 AM »

This well-preserved skull fragment�one of two newly found fossils that may help rewrite the story of human evolution�is believed to belong to the human ancestor species Homo erectus.

When viewed from above, the fossil�the smallest H. erectus skull ever found�is dwarfed by a similar skull discovered in Tanzania's Olduvai Gorge (inset).

The size difference suggests that H. erectus was more primitive than previously believed, with a social structure more similar to gorillas than modern humans.

Photograph by F. Spoor �2007 National Geographic/National Museums of Kenya; inset photograph by F. Spoor and J. Reader �2007 National Geographic/National Museums of Kenya

A new discovery suggests that Homo erectus may not have evolved from Homo habilis�and that the two may have been contemporaries.

The broken upper jaw-bone and intact skull from humanlike creatures, or hominids, are described in Nature.

Previously, the hominid Homo habilis was thought to have evolved into the more advanced Homo erectus, which evolved into us.

Now, habilis and erectus are thought to be sister species that overlapped in time.

The new fossil evidence reveals an overlap of about 500,000 years during which Homo habilis and Homo erectus must have co-existed in the Turkana basin area, the region of East Africa where the fossils were unearthed.

"Their co-existence makes it unlikely that Homo erectus evolved from Homo habilis," said co-author Professor Meave Leakey, palaeontologist and co-director of the Koobi Fora Research Project.

The jaw bone was attributed to Homo habilis because of its distinctive primitive dental characteristics, and was dated to around 1.44 million years ago.

It is the youngest specimen of this species ever found.

The skull was assigned to the species Homo erectus despite being a similar size to that of a habilis skull. Most other erectus skulls found have been considerably larger.

But it displayed typical features of erectus such as a gentle ridge called a "keel" running over the top of the jaw joint. Analysis showed the skull to be about 1.55 million years old.

The new dates indicate that the two species must have lived side by side.

Nature 448, 688-691 (9 August 2007) | doi:10.1038/nature05986; Received 12 March 2007; Accepted 5 June 2007
Implications of new early Homo fossils from Ileret, east of Lake Turkana, Kenya

F. Spoor1, M. G. Leakey2,3, P. N. Gathogo5, F. H. Brown5, S. C. Ant�n6, I. McDougall7, C. Kiarie8, F. K. Manthi8  &  L. N. Leakey2,4

   1. Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
   2. Koobi Fora Research Project, PO Box 24926, Nairobi 00502, Kenya
   3. Department of Anatomical Sciences,
   4. Department of Anthropology, Stony Brook University, Stony Brook, New York 11794, USA
   5. Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
   6. Department of Anthropology, New York University, New York, New York 10003, USA
   7. Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
   8. Division of Palaeontology, National Museums of Kenya, Nairobi 00100, Kenya

Correspondence to: F. Spoor1M. G. Leakey2,3 Correspondence and requests for materials should be addressed to F.S. (Email: ) or M.G.L. (Email: ).
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Sites in eastern Africa have shed light on the emergence and early evolution of the genus Homo1, 2, 3, 4, 5, 6. The best known early hominin species, H. habilis and H. erectus, have often been interpreted as time-successive segments of a single anagenetic evolutionary lineage3, 7, 8, 9, 10. The case for this was strengthened by the discovery of small early Pleistocene hominin crania from Dmanisi in Georgia that apparently provide evidence of morphological continuity between the two taxa11, 12. Here we describe two new cranial fossils from the Koobi Fora Formation, east of Lake Turkana in Kenya, that have bearing on the relationship between species of early Homo. A partial maxilla assigned to H. habilis reliably demonstrates that this species survived until later than previously recognized, making an anagenetic relationship with H. erectus unlikely. The discovery of a particularly small calvaria of H. erectus indicates that this taxon overlapped in size with H. habilis, and may have shown marked sexual dimorphism. The new fossils confirm the distinctiveness of H. habilis and H. erectus, independently of overall cranial size, and suggest that these two early taxa were living broadly sympatrically in the same lake basin for almost half a million years.

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