Seven million-year-old skull puzzles scientists

IN possibly the most startling fossil find in decades, scientists in central Africa have unearthed the oldest trace of a pre-human ancestor.

The remarkably intact skull, believed to be seven million-years-old, belonged to a previously unknown species that walked upright.

The thick-browed, flat-faced specimen was found in Chad, 1,500 miles west of earlier pre-human discoveries in east Africa.

The skull's age, physical appearance and location challenge basic beliefs about the evolution of humankind's earliest ancestors.

Scientists nicknamed the skull, Toumai, or "hope of life" in Africa's Goran language.

It was uncovered a year ago by a 40-person research team led by French palaeontologists in a remote, wind-scoured stretch of desert dunes, but has been kept from public view since. Other scientists who have examined the skull said it is a landmark, but enigmatic, specimen that raises more questions about humankind's presumed origins from the larger primate family.

"It is not what we thought we would find," said Bernard Wood of George Washington University. "If you look at the back of it, it looks like a chimpanzee, and if you look at the front of it, it looks like something in the human fossil record unambiguously a couple of million years ago."

Harvard anthropologist Dan Lieberman likened the find to Raymond Dart's 1920s discovery of a skull of an "ape-man" in southern Africa, which lent the first support to Charles Darwin's theory that the deepest traces of human evolution could be found on that continent.

"It is a major find," Mr Lieberman said. "It will take many years for us to understand just how important it is."

Dated between six and seven million years old, Toumai of the newly dubbed species Sahelanthropus tchadensis could be as much as one million years older than previously found hominid fossils, and at least three million years older than the next-oldest hominid skulls.

Last year, a 3.5 million-year-old skull was identified in Kenya by Meave Leakey. It was named Kenyanthropus platyops, or "flat-faced man of Kenya".