Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [95]
CHAPTERS 15, 16, 17 AND 18
The initial discovery of stone tool sites in the Hadar-Gona River area was made in the 1970s by Gudrun Corvinus, a German archaeologist, who was a member of Maurice Taieb’s expedition. Her work was followed by Hélène Roche, a French archaeologist, and then by an international team led by Sileshi Semaw, who carried out fieldwork in Gona between 1992 and 1994. Semaw’s team confirmed a date for the oldest tools found there as being 2.6–2.5 million years old. ‘The artefacts show surprisingly sophisticated control of stone fracture mechanics’, they reported in Nature in 1997.
The ‘tool factory’ at Kenya’s Lokalalei site was found by a team led by Anne Delagnes and Hélène Roche. They surmised that the tools were probably used partly to prepare food. Remains of ancient cattle, pigs, horses, rhinos and even crocodiles were found at the site. ‘The hominids likely lived in small groups exploring their environment for food procurement, either hunting or scavenging small game, or collecting fruits and plants’, said Delagnes.
The hobbit was discovered by a team led by Michael Morwood, an Australian archaeologist who tells the tale in A New Human (2007). An Australian anatomist, Peter Brown, studied the bones for three months before reaching a verdict in 2004. The announcement of the discovery triggered a worldwide debate. Analysing the foot bones, William Jungers of Stony Brook University, New York, suggested in 2009 that the ancestors of Homo floresiensis may not have been Homo erectus but ‘some other, more primitive hominid whose dispersal into southeast Asia is still undocumented’ (Nature 459: 81–84 [2009]).
Another puzzling discovery was made in 2008 by a team of Russian researchers excavating a rock shelter at Denisova in the Altai Mountains in Siberia. The cave site had previously yielded a collection of tools left behind by Neanderthals who had lived there between 48,000 and 30,000 years ago. Modern humans—Cro-Magnons—were also known to have lived in the same region at the same time. When the researchers dug up a section of finger bone at Denisova, they assumed that it belonged either to one of the Neanderthal inhabitants or to a modern human. But a small sample of mitochondrial DNA material extracted from the bone fragment told a different story: It matched that of neither Neanderthals nor modern humans.
Research results published in 2010 (Nature 468, 1012) showed that it belonged to a young girl from a new hominid lineage that researchers called Denisovan. Their conclusion was that Neanderthals and Denisovans were cousins, sharing a common ancestor that left Africa half a million years ago. While the Neanderthals spread westwards towards Europe, the Denisovans headed eastwards, inhabiting Siberia as recently as 30,000 years ago. Some Denisovans had interbred with sapiens groups migrating eastwards from Africa about 50,000 years ago: Genetic analysis of present-day occupants of Melanesia (Papua New Guinea and islands northeast of Australia) indicated they have inherited about 5 percent of their DNA from Denisovan roots.
Scientists are divided over whether there was a single migration out of Africa or a multiple exodus. Two Cambridge researchers, Robert Foley and Marta Lahr, argue in favour of at least two waves, an early one via the southern route to India and later migrations moving northwards via Suez and the Levant to Europe and Asia. Stephen Oppenheimer, an Oxford-based researcher, puts the case for a single exodus via southern Arabia. They also differ over the date of the first exodus. Oppenheimer places it before the Toba eruption 74,000 years ago. The Cambridge school believe that the first migration occurred nearer to 60,000 years ago. Spencer Wells describes the endeavours of geneticists to decipher the genetic code of modern humans. Nicholas Wade provides a masterful summary of recent research.
The fate of the Neanderthals