Scientists have concluded that Neanderthals were not the primitive dimwits they are commonly portrayed to have been.

The view of Neanderthals as club-wielding brutes is one of the most enduring stereotypes in science, but researchers who trawled the archaeological evidence say the image has no basis whatsoever.

They said scientists had fuelled the impression of Neanderthals being less than gifted in scores of theories that purport to explain why they died out while supposedly superior modern humans survived.

Wil Roebroeks at Leiden University in the Netherlands said: "The connotation is generally negative. For instance, after incidents with the Dutch Ajax football hooligans about a week ago, one Dutch newspaper piece pleaded to make football stadiums off-limits for such 'Neanderthals'."

The Neanderthals are believed to have lived between roughly 350,000 and 40,000 years ago, their populations spreading from Portugal in the west to the Altai mountains in central Asia in the east. They vanished from the fossil record when modern humans arrived in Europe.

The reasons for the demise of the Neanderthals have long been debated in the scientific community, but many explanations assume that modern humans had a cognitive edge that manifested itself in more cooperative hunting, better weaponry and innovation, a broader diet, or other major advantages.

Roebroeks and his colleague, Dr Paola Villa at the University of Colorado Museum in Boulder, trawled through the archaeological records to look for evidence of modern human superiority that underpinned nearly a dozen theories about the Neanderthals' demise and found that none of them stood up.

"The explanations make good stories, but the only problem is that there is no archaeology to back them up," said Roebroeks.

Villa said part of the misunderstanding had arisen because researchers compared Neanderthals with their successors, the modern humans who lived in the Upper Palaeolithic, rather than the humans who lived at the same time. That is like saying people in the 19th century were less intelligent than those in the 21st because they didn't have laptops and space travel.

"The evidence for cognitive inferiority is simply not there," said Villa. "What we are saying is that the conventional view of Neanderthals is not true." The study is published in the journal Plos One.

So what did kill off our equally intelligent extinct cousins? Roebroecks said that the reasons must have been complex, and that recent genetic studies that have decoded the Neanderthal genome might reveal some clues. Those studies show that Neanderthals lived in small, fragmented groups, and interbred to some extent with modern humans. Some of their inbred male offspring were infertile. The arrival of modern humans may simply have swamped and assimilated them.

"Stereotypes help people to order their world, but the stereotype of the primitive Neanderthal is now gradually eroding, at least in scientific circles," said Roebroecks.