Hunting by humans has often been put forward as a contributory cause of extinctions of the Pleistocene megafauna. The team, though, said their new date for the Irish elk's extinction hints at an additional human-made problem—habitat destruction.

Lister said, "We haven't got just hunting 7,000 years ago—this was also about the time the first neolithic people settled in the region. They were farmers who would have cleared the land."

The presence of humans may help explain why the Irish elk was unable to tough out the latest of many climatic fluctuations—periods it had survived in the past.

Meanwhile, Lister cast doubt on another possible explanation for the deer's demise—the male's huge antlers.

Some scientists have suggested this exaggerated feature—the result of females preferring stags with the largest antlers, possibly because they advertised a male's fitness—contributed to the mammal's downfall. They say such antlers would have been a serious inconvenience in the dense forests that spread northward after the last ice age.

But, Lister said, "That's a hard argument to make, because the deer previously survived perfectly well through wooded interglacials [warmer periods between ice ages]."

Moose Competition

He added, however, that the animal may have also suffered from increased competition from other species such as moose, which spread rapidly once the climate warmed.

U.S. scientists from the University of Minnesota say the new study makes it clear that the reasons why so many Ice Age mammals went extinct are far more complex than previously realized.

Writing independently in tomorrow's Nature, biologists John Pastor and Ron Moen state: "The [Irish elk] finding lends weight to the idea that there is no one explanation for the so-called Pleistocene extinctions."

Alongside climate fluctuations and vegetation changes, they say, human activity, competing species, and other ecological pressures need to be taken into account for each animal.

Lister said, "Whereas people have been looking for single blanket explanation to account for all these species going extinct, we're saying you've got a range of species with different ecologies and adaptations."

So while the Irish elk preferred relatively temperate conditions and semi-woodland habitats, the woolly mammoth was adapted to cold temperatures and open tundra.

"Past climate changes would have impacted on those two species differently," Lister added.

And if the mammoth and Irish elk both survived, what of the other shaggy megafauna that supposedly perished during the last ice age? The woolly rhinos and cave bears of Europe and Asia, the saber-toothed cats, the mastodons and giant sloths of North and South America—could some of these have made it through too?

"It's entirely possible," Lister said. "I think there are all sorts of surprises around the corner."

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SOURCES AND RELATED WEB SITES Nature Irish Elk Department of Biology, University College London