Interspecies sex between ancient humans and Neanderthals – a relative of our ancestors who had smaller figure and low, flat, elongated skulls like dwarfs in the in The Lord of the Rings – had given 1.6 to 1.8 percent Neanderthals' gene to every one in Europe and Asia nowadays.

An International research team led by Fu Qiaomei from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences shows the reason that we did not inherit the dwarfs' figure is because their gene was eliminated by the process of natural selection.

The research drew the conclusion after analyzing genome-wide data from 51 Eurasians lived 45,000 to 7,000 years ago. Their findings were published as in Nature on Monday.

"Before our research, it was believed that the decrease in the proportion of Neanderthal ancestry in Eurasians was the result of interspecies sex with other human groups that diluted the Neanderthal's gene," said Fu.

"However, our research finds that the Neanderthal's gene decreased fast and steadily from between 37,000 and 14,000 years ago, in a period that there was not major admixture of other population outside of Europe."

Over this period of time, the proportion of Neanderthals ancestry in Eurasians decreased from six percent to around two percent within descents of a single founding population.

"This suggests that the Neanderthal's gene was eliminated in the evolution," Fu said.

Moreover, the influence of Neanderthal's origin in modern human is more muted in major functional gene fragments than in other genome parts, which points to the same conclusion.