Evidence of a human presence in Australia 62,000 years ago at Lake Mungo, which is located in the interior of Australia, was seen by some as a dagger in the heart of the Out of Africa theory.
"Some [scientists] argued that the previous estimate of 62,000 years for Mungo 3 was a problem for Out of Africa, but I didn't think so," said Chris Stringer, director of the Human Origins program at the Natural History Museum in London.
Stringer and colleagues support the idea that at least one wave of migration out of Africa preceded the exodus that occurred 50,000 years ago, and that the earliest journeyers reached Australia.
"Modern humans had plenty of time to reach Australia," he said. "A rate of movement from Africa averaging only one mile a year along the coasts of southern Asia would have got people to within a boat ride of Australia in less than 10,000 years."
The revised dates lend additional credence to the Out of Africa model and are consistent with evidence from other sites in Australia.
"This agrees very well with genetic data suggesting a settlement of northern Australia no earlier than 50,000 to 55,000 years ago," said Spencer Wells, geneticist and author of the recently published book The Journey of Man: A Genetic Odyssey. Wells uses Y-chromosome data to trace the paths taken by early humans as they left Africa.
"It's speculation, of course, but perhaps the first Australians moved inland via the river systems of Queensland and southern Australia. The riverbanks would effectively be an extension of the coastal environments they were living in en route from Africa, and could have brought them to Lake Mungo by around 45,000 years ago," he said. "The new dates are exciting, and provide strong support for a recent (post-60,000 years ago) 'Out of Africa' exodus."
Living at Lake Mungo
Today Lake Mungo is a semi-arid landscape supporting saltbush stands, a shrub that thrives in salty or alkaline sites where very few other plants can survive. But 60,000 years ago, vegetation was lush and the lake's water levels remained relatively high, with only brief and relatively minor changes, for about 15,000 years.
"We believe the lakeshore was populated by small communities, perhaps on a seasonal basis," said Bowler. "They were almost certainly congregating around the disappearing water resources as the country began to dry out in advance of the really big drought that began around 40,000 years ago, immediately after the Mungo Lady and Mungo Man burials."
More than 775 artifacts discovered at the site provide a glimpse of life at Lake Mungo in prehistoric times. The people hunted small game, gathered mussels and other shellfish from the lake and fished for cod and perch, possibly using nets.
"My own view is that most fish were caught during periods in which the lake was falling, increasing the salinity of the water and making the fish groggy and easy to catch," said Bowler.
These early humans also had ritualistic burial practices; Mungo Woman was cremated, the remaining bones smashed, burned again, and then buried. Mungo Man's body had been covered with red ochre prior to burial. Anthropologists consider burying the dead an indicator of a spiritual belief system and a hallmark of modern humans.
Beginning around 40,000 years ago, the climatic and environmental conditions in the region became much harsher: the lake gradually dried up, temperatures were colder, the landscape more barren and inundated with dust. Humans responded accordinglythey moved on.
"They did return several thousand years later during a period when the waters returned," said Bowler. But the climatic changes were part of the long slide into the last ice age, which occurred about 20,000 years ago.
Today Lake Mungo is part of the Willandra Lakes World Heritage Area, and considered a sacred ancestral site of the Aborigines.
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