Mammoths survived late in Britain

Woolly mammoths lived in Britain as recently as 14,000 years ago, according to new radiocarbon dating evidence.

Dr Adrian Lister obtained new dates for mammoth bones unearthed in the English county of Shropshire in 1986.

His study in the Geological Journal shows the great beasts remained part of Britain's wildlife for much longer than had previously been supposed.

Mammoths may finally have died out when forests encroached on the grassland habitats they favoured for grazing.

The radiocarbon results from the adult male and four juvenile mammoths from Condover, Shropshire, reveal that the great beasts were in Britain more than 6,000 years longer than had previously been thought.

Researchers had supposed that mammoths disappeared from North-West Europe between 21,000 and 19,000 years ago, during a climatic freeze known as the last glacial maximum (LGM).

Britain's mammoth populations may indeed have vanished with this big chill.

But according to the new study, they were not gone forever. Instead, they returned when conditions eased and clung on in southern England until 14,000 years ago.

"What this usually means is that (mammoths) die out locally and then re-emigrate from refugia somewhere else," Dr Lister told BBC News.

Purification method

The specimens have been radiocarbon dated before. But the Natural History Museum researcher used a relatively new method of radiocarbon dating to get very accurate ages for the Condover fossils.

"The big issue with all radiocarbon dating is contamination from different sources. You have to be sure the sample you extracted from the fossil is absolutely pure," said Dr Lister.

"There have to be methods for purifying the sample that is extracted from the bone. In the last few years, a new method of purification has been developed at Oxford University called ultra-filtration."

"Various bone specimens that were dated before they developed this new purification method have been shown to be out by a significant amount. Not always, but often. What they do is re-run the sample using the new method and obtain a more accurate date. That's what we did here."

Other large mammals that disappeared as the last Ice Age relented include woolly rhino, bison and giant deer.

At the same time as these species were vanishing from the Earth, human populations were expanding.

Similar die-outs of so-called "megafauna" occurred around the world at similar times, prompting some scientists to ask whether climate or human hunting played the dominant role in their extinction.

Human question

No traces of human occupation were found at the Shropshire site. But it is entirely possible that humans could have been in Britain at the same time as these last mammoths.

Dr Lister said that humans might have finished off some of the last remaining pockets of mammoths in Siberia. But he did not think people were the main cause of megafaunal extinctions at the end of the last Ice Age.

During the Ice Age, grasslands were commonplace in Europe because conditions were too cold for trees.

But as the climate warmed up, forests began to spread north, squeezing out the grassland habitats favoured by the majestic beasts.

"It's driven by climate change, but it's not the climate - in the main - that affects these animals. The climate affects the vegetation and the vegetation affects them," said Dr Lister.

"These were grass-eating animals."

Mammoths first appeared in the Pliocene Epoch, about 4.8 million years ago.

One population lived on in isolation on Russia's remote Wrangel Island until about 5,000 years ago, making them the most recent surviving population known to science.

Paul.Rincon-INTERNET@bbc.co.uk

http://news.bbc.co.uk/1/hi/sci/tech/8106090.stm