回答 [Recent Tests- VOL] - Mungo Lady and Mungo Man

Controversies in Australian Prehistory

Fifty thousand years ago, a lush landscape greeted the first Australians moving towards the south-east of the continent. Temperatures were cooler than now. Megafauna - giant prehistoric animals such as marsupial lions and the rhinoceros-sized diprotodon - were abundant. Freshwater lakes in areas of western New South Wales (NSW) were brimming with fish. But change was coming. By 40,000 years ago, water levels had started to drop.

A study of the sediments and graves of Lake Mungo, a dry lake bed in western NSW, has uncovered the muddy layers deposited as the lake began to dry up. 9-10Forty thousand years ago, families took refuge at the lake from the encroaching desert, leaving artefacts such as stone tools,9 which researchers used to determine that the first wanderers came to the area between 46,000 and 50,000 years ago. By 20,000 years ago, the lake had become the dry, dusty hole it is today. This area was first examined by the University of Melbourne geologist Professor Jim Bowler in 1969. He was searching for ancient lakes and came across the remains of a woman who had been buried with some ceremony; she was given the name 'Mungo Lady'. In 1974, he found a second set of remains, Mungo Man, buried 500 metres away. Bowler's comprehensive study of different sediment layers has concluded that both graves are 40,000 years old.

This is much younger than the 62,000 years Mungo Man was attributed with in 1999 by a team led by Professor Alan Thorne, of the Australian National University. Thorne is the country's leading opponent of the 'Out of Africa' theory - that modern humans spread around the globe from Africa about 100,000 years ago. The revision of Mungo Man's age has refocused attention on academic disputes about humankind's origins.

The arrival date of these early Australians is linked to another vexed question: the reason for the disappearance of the megafauna. 3Dr Tim Flannery, a proponent of the controversial theory that these animals were wiped out by the extreme hunting practices of humans, claims that the new Mungo dates support this view. For Bowler, however, these debates are speculative distractions. 8At 40,000 years old, he argues, Mungo Man and Mungo Lady remain Australia's oldest human burials and the earliest evidence on Earth of cultural sophistication. 'At Lake Mungo, we have a cameo of people reacting to environmental change. It is one of the great stories of the people of the world.'

Two rival groups of researchers have each attacked the techniques used by the other to ascertain the date of Mungo Man. 12In the 1999 study, Thorne's team used three techniques to date Mungo Man - bone, tooth enamel and sand. 13Bowler has strongly challenged the results ever since. Dating human bones is notoriously unreliable, he says. In addition, the sand sample used by Thorne's group was taken hundreds of metres from the burial site.

Bowler has stated that it is not difficult to realise that the age of sand is not the same as the age of the grave. 13He says his team's results are based on careful fieldwork, crosschecked between four laboratories, while Thorne's team misinterpreted the evidence, 'locked in a laboratory in Canberra'. Thorne counters that Bowler's team used one dating technique, while his used three. Best practice is to have at least two methods producing the same result. 4A Thorne team member, Professor Rainer Grün, says the fact that the latest results were consistent between laboratories doesn't mean they are correct.4-11 'We now have two data sets that are contradictory. I do not have a plausible explanation.'

1Thorne recently made headlines with a study of Mungo Man's DNA, which he claimed supported his idea that modern humans developed from archaic humans in several places around the world, rather than emerging from Africa a relatively short time ago. 5-11Now, however, Thorne says the age of Mungo Man is fiercely disputed.5 Recent fossil finds show that modern humans were in China 110,000 years ago. So he has a long time to arrive in Australia. It doesn't matter if he is 40,000 or 60,000 years old.

2In 2001, a member of Bowler's team, Dr Richard Roberts of Wollongong University, along with Flannery, Director of the South Australian Museum, published research on the extinction of the megafauna. They dated 28 sites across the continent, arguing that their analysis showed that the megafauna died out suddenly 46,600 years ago. 6This conclusion has been challenged by other scientists, including Dr Judith Field of Sydney and Dr Richard Fullagar of the Australian Museum, who point to the presence of megafauna fossils at the 36,000-year-old Cuddie Springs site in NSW.

Flannery praises the Bowler team's research as thorough and rigorous. 7He says the finding that humans arrived at Lake Mungo between 46,000 and 50,000 years ago supports the idea that that was a critical time in Australia's history. There is evidence of a dramatic climate change at that time, he says. 'It's my view that humans arrived and megafauna extinction took place in almost the same geological instant’. Bowler, however, is sceptical of Flannery's theory about the disappearance of the giant animals. He argues that climate change 40,000 years ago was more intense than has been previously realised and could have played an important role in their extinction.