|
The story about human evolution might be rewritten. For decades scientists have worked to connect the dots between dozens of fossil discoveries in East and southern Africa in hopes of constructing an accurate picture of human origins. D.L. Parsell, National Geographic News, Updated 11 July, 2002.
Now, a new find in western Central Africa suggests the picture may be radically different than widely assumed. A team of researchers excavating in northern Chad has unearthed the well-preserved skull and other fossilized remains of what they believe was a previously unknown hominid, or early human precursor, that lived six to seven million years ago. That date would make it the oldest known ancestor of humans.
The finding has excited the scientific community especially because it opens a window onto a period near the time when humans and apes diverged from a common ancestor. Virtually nothing about that period is known, as most human fossils are considerably younger. Various aspects of the new fossils could force scientists to rethink some basic theories about human origins, according to several scientists who were not part of the research team.
New Genus, New Species
Michel Brunet of the University of Poitiers in France headed the international team of more than three dozen researchers. They found the fossilsan intact cranium, two lower jaw fragments, and several teethat a site in the Djurab Desert where the group has been excavating since the mid-1990s. The researchers compared the ancient skull and related fossils with the fossils of many other known hominids and primates. Based on characteristics such as the tooth type and the thickness of the enamel, the shape and positioning of the head, and the facial features, the team concluded that the creature represented a new genus and species of hominid.
They officially named it Sahelanthropus tchadensis. Its nickname is "Toumaë," a Goran-language word meaning "hope of life"; in the Djurab Desert, the name is given to babies born just before the dry season.
Brunet's team found the ancient skull last year and hoped to keep it secret until after the findings underwent scientific review. But rumours and brief news reports about the discovery in European newspapers set off a buzz of excitement in the scientific community. The discovery follows several other hominid fossil claims in recent years that have pushed the search for our human ancestors much further back in time. Some of those fossils are nearly as old as Sahelanthropus.
Nonetheless, scientists say the skull found in Chad stands apart as remarkable for a number of reasons, including its age and completeness. The desert site in northern Chad where Sahelanthropus was found is 1,500 miles (2,500 kilometres) west of Africa's Rift Valley. The east side of the Rift Valley has long been regarded as the "cradle of humanity" because of the abundant hominid fossils recovered there.
Realize how limited a view we have of human evolution because until now we've concentrated on East Africa," he said. The Rift Valley has long been associated with early human evolution because many scientists believe the opening of the rift millions of years agowhich left jungle on the west and savannah or grasslands to the eastwas an important factor that helped shape adaptation. One widely held theory suggests that early human ancestors became bipedalwalking uprightwhen they moved out of forests and trees and into savannas. Presumed traits of the new hominid are somewhat at odds with that view.
The region where Sahelanthropus dwelled was teeming with other animals, according to Brunet and his colleagues. Since 1994, they have recovered tens of thousands of vertebrate fossils from the excavation site in northern Chad. The fossil remains represent 42 species that include elephants, giraffes, antelopes, hippopotamus, crocodiles, lizards, monkeys, fish, and wild boar.
As National Geographic says it: the Skull Fossil Opens Window Into Early Period of Human Origins. Exactly where Sahelanthropus belongs on the family tree is not possible to determine at this time. Despite the detailed analysis and published claims, the question of identity remains open-ended. Is it actually a new hominid, or a variation of some other previously identified species, or perhaps even an ape? Things are much more diverse than we ever have thought of.
Stein Morten Lund, 27. September 2003
Additional information
For more information about great discoveries, read more about on our website - see the link to Expeditions.
Travel Explorations keep you updated with great news about expeditions and discoveries.
More information about human origins and other discoveries can be found on National Geographic's website www.NationalGeographic.com
|
E-mail this
Print this
