Scientists have long debated what caused the Neanderthals to die off. A new study has suggested that a flood of prehistoric humans pouring into Europe inundated our ancient rivals and overwhelmed them with sheer force of numbers.

Neanderthals departed Africa about 400,000 to 800,000 years ago, and subsequently evolved in lands that now comprise France, Spain, Germany and Russia. They are believed to have died out (or absorbed into the modern human population) about 30,000 years ago.

A new study published in the journal Science found that humans outnumbered Neanderthals by about 10 to one in a region of Southwest France, and its authors believe that a massive influx of humans migrating from Europe overwhelmed Neanderthals in the competition for resources.

"Numerical supremacy alone may have been a critical factor" in humans surviving, the study's authors wrote.

After studying archaeological evidence from both Neanderthal and Homo sapien sites in southwest France, which contains the largest concentration of Neanderthal and early modern human sites in Europe, researchers concluded that humans far outnumbered their Neanderthal counterparts. There was also evidence that humans had superior hunting techniques and better social ties with other communities of humans.

The study was conducted by two researchers from the Department of Archaeology at Cambridge – Professor Sir Paul Mellars, Professor Emeritus of Prehistory and Human Evolution, and Jennifer French, a second-year PhD student.

"It was clearly this range of new technological and behavioral innovations which allowed the modern human populations to invade and survive in much larger population numbers than those of the preceding Neanderthals across the whole of the European continent," Mellars said.

"Faced with this kind of competition, the Neanderthals seem to have retreated initially into more marginal and less attractive regions of the continent and eventually -- within a space of at most a few thousand years -- for their populations to have declined to extinction -- perhaps accelerated further by sudden climatic deterioration across the continent around 40,000 years ago."

“The study was too simplistic. The overwhelming genetic and paleontological evidence shows what happened was assimilation, not replacement." His statement seems to be supported by a recent study finding that most humans are genetic descendants of Neanderthals, which suggests that humans and Neanderthals mated with one another,” said Joao Zilhao, a research professor at the University of Barcelona.

Neanderthals were thought to have created symbolic objects such as jewelry and to have formulated language, making them the closest known thing to humans. Considerable debate remains as to whether they are subsets of the same species or if they are distinct.

The human/Neanderthal dichotomy was overturned in Dec. 2010, when a team of researchers discovered fossil evidence of a third humanoid species, dubbed the "Denisovans," that roamed Asia and may be the ancient forefathers of people in Papua New Guinea.