Many of the archaeological finds have occurred along the east coast of England, where there has been dramatic coastal erosion in recent years.
The earliest evidence for human occupation in the British Isles has been discovered at Pakefield, a site dated to 700,000 years ago and located near Lowestoft on Britain's east coast.
No human remains were found, but more than 30 flint tools have been unearthed, providing sufficient proof of human occupation.
Animal and plant fossils from the same time period show that Pakefield was once very different.
"The climate was almost Mediterranean, and there were animals like hippopotamuses, hyenas, and lions roaming around," said Simon Parfitt, a mammal fossil specialist based at the Natural History Museum in London.
It's hard to say what the Pakefield people were like, Parfitt says. But the kind of tools they used and the animals they hunted indicate that the Pakefield settlers were more human than ape.
"Essentially they would have been very robust early humans, who walked about on two legs and subsisted from hunting and gathering," he said.
The next wave of immigrants appears to have developed more sophisticated tools such as hand axes.
At Happisburgh, also on the east coast of England, the scientists discovered huge piles of butchered animal bones and hand axes at least 500,000 years old.
The majority of the finds have been in the south of the British Isles. "Ice sheets would have ground everything to pieces further north," Parfitt explained.
But that doesn't mean that early humans didn't go farther north. Some evidence of settlement has been found in Wales and in England's Midlands and north.
After several more unsuccessful incursions, the Neandertals (often spelled "Neanderthals") strode over to the British Isles around 60,000 years ago and survived by hunting big game, researchers say.
At a quarry near Norwich, in eastern England, Durham University's White and his colleagues have been examining a woolly mammoth butchery site.
The Neandertals appear to have been picking off the weakest of the beasts and herding them into a swampy area to kill them.
The findings are changing the way that scientists perceive the Neandertal people. "It seems they were a lot more savvy than people give them credit for," White said.
Nonetheless, the Neandertals couldn't withstand the extreme cold and were pushed out by the next ice age. (Related: "Neandertals' Last Stand Was in Gibraltar, Study Suggests" [September 18, 2006].)
Around 20,000 years ago the world experienced its most recent glacial period. The ice gradually retreated, and by around 12,000 years ago the modern British population began to arrive.
Most glacial cycles are believed to occur because of changes in planetary motions known as Milankovitch cycles. All across northern Europe, Russia, and China, ancient peoples were likely to have followed the advance and retreat of the ice sheets, scientists say.
However, humans didn't always take advantage of the warm periods in Britain.
"There were four warm periods where the ice retreated, but humans, as far as we know, didn't come," White said.
The sea level may have been too high for them to cross, or perhaps they were just content to stay in continental Europe, he says. Or evidence of their presence in Britain during these periods may just not have been found yet.
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