With Adam From Out Of Africa

Fossil finds near an Ethiopian village dating 
back 160,000 years nail several theories, reports Biplab Das 

While "Eve" still eludes palaeoanthropologists, some fossil hunters may have stumbled upon the remains of what may have been her "Adam" and child in a dry and dusty valley bordering the Middle Awash river near Herto, a village in the Afar region of Ethiopia. The two fossilised skulls they have found date back 160,000 years, around about the time "Eve" walked the earth according to scientists who studied a stretch of DNA of mitochondria, which is passed from mother to daughter. 

The fossilised skulls also shed light on what happened during the transition from the pre-humans stage. "We have lacked intermediate fossils between 100,000 and 300,000 years ago when the transition was taking place, and that is where the Herto fossils fit," said palaeoanthropologist Tim White, a professor of integrative biology at the University of California, Berkeley and a co-leader of the team that excavated the skulls. "Now, the fossils record reconciles with the molecular evidence. With this new crania, we can now see what our direct ancestors looked like." 

In this research, Berhane Asfaw of the Rift Valley Research Service in Addis Ababa, Ethiopia, and Giday WoldeGabriel of Los Alamos National Laboratory in New Mexico support White and his colleagues. The results of the find have been reported in two papers published in the 12 June issue of Nature. 

Herto's fossil-rich site was first identified on 16 November 1997. This was where White first encountered stone tools and a fossil skull of a butchered hippopotamus. Excited, he returned 11 days later to find many more fossils thrown up by soil eroded by heavy rains. Crushed and scattered pieces of two adult braincases protruded from the ground. The ground close to where these skulls were found was littered with pieces of bone from a child's skull. 

Asfaw painstakingly pieced together the child's bones. From the teeth, it was assumed that the child died at the age of seven. Marks indicated that, after death, the muscles had been removed from the base of the skull. The adult skulls also bore cut marks that promoted the conclusion that the Herto people had elaborate mortuary practices. 

The Herto skulls were found some distance away from other bones from the rest of the bodies, which was unusual, White said. "This leads researchers to infer that the people were moving the heads around the landscape." They probably broke the skulls to extract the brain. "But we have no way of knowing whether it was a part of a cannibalistic ritual," he added. 

Around 200,000 years ago, the Middle Awash river was a shallow lake, home to hippos, crocodiles and catfish, while buffalo roamed the vicinity. The Herto people lived along the shores of the lake and were intrepid hunters, the hippo bones found alongside the skulls testifying to their skill. They used sophisticated stone tools like hand axes, flake tools, cores and rare blades. "Using chipped hand axes and other stone tools, they were butchering carcasses of large animals like hippos and buffalo and undoubtedly knew how to exploit plants," White said. 

The reconstructed fossil skulls have sounded the death knell for many theories. The anatomical features of the skulls prove that we have not descended from Neanderthals. "Neanderthals split off from the main branch of the human family tree more than 300,000 years ago and died out about 30,000 years ago," White said. The Herto fossils provide strong support for the hypothesis that modern humans evolved in Africa and subsequently spread into Eurasia. The fossil evidence, said Asfaw, clearly showed that modern humans were living around 160,000 years ago with full-fledged Homo sapiens features. 

The Herto finds shift the focus of human evolution once again to East Africa, writes Chris Stringer, an anthropologist from the Natural History Museum, London, in a commentary article in the same issue of Nature. Because in this single study area the research team found fossils dating from the present to more than six million years ago, painting a clear picture of human evolution from ape-like ancestors to present-day humans. 

The Herto descendants and other contemporary African people spread across the continent and did not venture out of Africa until 70,000 years ago, according to a new study by geneticists from Stanford University and the Russian Academy of Sciences. The results of the study were published in the May issue of the American Journal of Human Genetics. In their study, the research team compared 377 snippets of DNA called microsatellite markers. These DNA snippets were collected from 1,056 individuals representing 50 geographic sites in Africa, the Middle East, Europe, Central and South Asia, East Asia, Oceania and the Americas. The study revealed that only about 2,000 wanderers left Africa. 

"This study, however, does not preclude the presence of other populations of Homo sapiens in Africa," said Marcus W Feldman, an anthropologist from Stanford University and co-author of the study. "Although it suggests that they were probably isolated from one another genetically and that contemporary worldwide populations descend from one or very few of those populations." 

According to Feldman, the results support the out-of-Africa theory, which says a small group of the sub-Saharan African population gave rise to all populations of anatomically modern humans through a chain of migrations to the Middle East, Europe, Asia, Oceania and the America. For these migrating people, hunting and gathering was an uncertain way of living. "They faced severe population bottlenecks during which their numbers crashed - possibly because of limited resources, disease and, in some cases, the effects of long distance migrations," Feldman explained. 

A few genetic mutations might have fuelled the meteoric shift in technological and cultural innovations. "The technological innovations increased the overall survival and birth rate of hunter-gatherers," wrote Feldman and his colleagues. As a result, peoples scattered all over the globe bounced back in numbers. 

Richard Klein, an anthropologist from Stanford University, also links the emergence of innovative and creative humans to genetic mutation. "There was a biological change - a genetic mutation of some kind that promoted the fully modern ability to create and innovate," he said at recent symposium on Revolution and Evolution in Modern Human Origins: When, Where and Why? The American Association for the Advancement of Science organised the symposium in Denver. The ancestors of modern sub-Saharan African farming populations increased in numbers around 35,000 years ago. The peoples of Eurasia and East Asia also show evidence of population increase starting about 25,000 years ago. 

About 10,000 years ago, the retreat of the last ice age and the advent of farming drove our ancestors to abandon the life of the hunter-gatherer. Since then, we have never looked back. From a couple of thousand, we are now over six billion-strong, occupying every patch of habitable land on earth. But we cannot contradict our long forgotten African relatives. Fossils and genes remind us that we are indeed "Africans under the skin".