NEW SKULL FOSSILS CHALLENGE THE THEORY OF MAN'S ORIGIN

Ten million-year-old fossils discovered in Ethiopia show that humans and apes probably split six or seven million years earlier than widely thought, according to landmark study released Wednesday.

The handful of teeth from the earliest direct ancestors of modern gorillas ever found -- one canine and eight molars -- also leave virtually no doubt, the study's authors and experts said, that both humans and modern apes did indeed originate from Africa.

The near total absence to date of traces on the continent of apes from this period had led many scientists to conclude that the shared line from which humans and living great apes emerged had taken a long evolutionary detour through Eurasia.

But the study, published in the British journal Nature, "conclusively demonstrates that the Last Common Ancestor (of both man and ape) was strictly an African phenomenon," commented paleoanthropologist Owen Lovejoy of Kent State University in Ohio.

Lovejoy described the fossils as "a critically important discovery," a view echoed by several other scientists who had read the paper or seen the artifacts.

"This is a major breakthrough in our understanding of the origin of humanity," Yohannes Haile-Selassie, a physical anthropologist at the Cleveland Museum of Natural History, told AFP.

The most startling implication of the find, the scientists agree, is that our human progenitors diverged from today's great apes -- including gorillas, orangutans and chimpanzees -- several million years earlier than widely accepted research based on molecular genetics had previously asserted.

The trail in the hunt for physical evidence of our human ancestors goes cold some six or seven million years ago.

Orrorin -- discovered in Kenya in 2000 and nicknamed "Millennium Man" although its sex remains unknown -- goes back 5.8 to 6.1 million years, while Sahelanthropus, found a year later in Chad, is considered by most experts to extend the human family tree another one million years into the past.

Beyond that, however, fossils of early humans from the Miocene period, 23 to five million years ago, disappear. Fossils of early apes especially during the critical period of 14 to eight million years ago were virtually non-existant -- until now.

"We know nothing about how the human line actually emerged from apes," the authors of the paper noted.

But the new fossils, dubbed "Chororapithecus abyssinicus" by the team of Japanese and Ethiopian paleoanthropologists who found them, place the early ancestors of the modern day gorilla 10 to 10.5 million years in the past, suggesting that the human-ape split occurred before that.

There is broad agreement that chimpanzees were the last of the great apes to split from the evolutionary line leading to man, after gorillas and, even earlier, orangutans.

Conventional scientific wisdom, based on genetic "distances" measured by molecular geneticists, had placed the divergence between chimps and humans some five to six million years ago. Orangutans are thought to have parted company with our ancestors 13 to 14 million years ago.

"If the new discovery is in the gorilla lineage, then this will definitely substantially push back the split time between apes and humans," Halie-Selassie at Kent State told AFP.

The scientists leading the team that found the fossils -- Gen Suwa of the University of Tokyo, and Ethiopian paleontologists Berhane Asfaw and Yonas Beyene -- calculated that the human-orangutan split "could easily have been as old as 20 million years."

They determined that the teeth belonged to gorilla ancestors based on unique shared characteristics of the molars, which had evolved for a diet of fibrous foods such as stems and leaves.

The match is not exact, however, and could prompt some scientists to challenge the findings.

The teeth fragments, found in barren scrubland some 170 kilometres (100 miles) east of Ethiopia's capital Addis Ababa, almost went unnoticed.

Asfaw recalled the chance discovery.

"It was our last day of field survey in February 2006, and our sharp-eyed field assistant, Kampiro, found the first ape tooth, a canine," he said.

"He picked it up and showed it to me, and I knew that this was something new -- Ethiopia's first fossil great ape."

FOSSIL CASTS DOUBT ON THE ORIGIN OF MAN

t all seems so simple on the evolution diagrams we are used to seeing.

The ape gradually stops dragging its arms along the ground, becomes upright and evolves into modern man - the homo sapien.

But the analysis of two fossils from Kenya is throwing all that into question.

Research published in the journal Nature today has thrown up a serious challenge to the widely accepted view on human evolution.

An international team of researchers, including a geologist from the Australian National University (ANU), has found that two different species of early man lived side by side in the same place for almost half a million years.

Susan Anton is an associate professor of anthropology at New York University and co-author of the research.

"The co-existence of the two species suggests that they were more like sister species, as opposed to homo habilus being the mother to homo erectus," she said.

Assumptions in doubt

ANU geologist Ian MacDougall was part of the research team that travelled to the Koobi Fora Formation in Kenya.

He says the work throws up a whole host of questions.

"It would suggest that the two species lived in the same area but must have different ecological niches, as it were," he said.

"They weren't seriously competing, otherwise one would have expected the one species to completely dominate, and in fact wipe out a less adaptive species.

"It really does throw into doubt a whole series of assumptions that have previously been made on the basis of the fossils."

Mr McDougall is cautious about rushing to conclusions that history needs to be re-written.

"I don't think it throws into question the linear model from [homo] erectus to [homo] sapien," he said.

"But who knows what will turn up tomorrow?

"It makes it just a little more complicated, and that's been the story of the discussions on prominent evolution and particularly these early fossils found in Africa.

"The evolutionary tree is much more bushy than was thought even 10 years ago."

Disagreement

Colin Groves, professor of biological anthropology at the ANU, has long argued that the linear model of evolution is far too simple. He welcomes this new work.

"The general public seems to have the idea that evolution sort of progresses onward and upward," he said.

"But for a long time it's become clearer and clearer that - just like any other species - human evolution consists of divergent species coming off and new species arising.

"The idea of human evolution as a ladder, I think, is impossible to maintain anymore."

There is some disagreement about the implications of the study.

The researchers say it indicates that homo erectus and homo habilis both descended from another species.

Other scientists say it merely shows that an ancestral being can survive for a long time alongside its descendant.

The debate continues.