Neanderthals were a distinct species from modern humans, scientists say. Gianfranco Goria/Flickr

Neanderthals were not a sub-species of modern humans and they were killed off by competition with our ancestors, researchers have said.

Previously, it was thought Neanderthals were a sub-species of human, but growing evidence suggests they were a distinct species completely separate from Homo sapiens.

Researchers led by the New York's SUNY Downstate Medical Centre examined the nasal complex of Neanderthals and found it was not adaptively inferior to that of modern humans.

They also found that Neanderthals' extinction was due to competition from modern humans, not because their noses were unable to process a colder and drier climate, has was previously suggested.

Published in a special issue of The Anatomical Record, the team suggest that studies of the Neanderthal nose over the last 50 years have been approaching the anatomy from the wrong perspective.

Instead of comparing the Neanderthal nose to modern humans, such as modern Europeans who are adapted to cold and temperate climates, researchers say Neanderthals functioned by a different set of rules because of a separate evolutionally history.

This would have resulted in a mosaic of features not found among any populations of modern humans. As a result, the team came to the conclusion that Neanderthals could not have been a sub-species of modern humans.

Professor Jeffrey T. Laitman, who worked on the study, said: "The strength of this new research lies in its taking the totality of the Neanderthal nasal complex into account, rather than looking at a single feature. By looking at the complete morphological pattern, we can conclude that Neanderthals are our close relatives, but they are not us."

Ian Tattersall, expert on Neanderthal anatomy and functional morphology who did not participate in this study, said: "[The researchers] have carried out a most provocative and intriguing investigation of a very significant complex in the Neanderthal skull that has all too frequently been overlooked.

"With luck, this research will stimulate future research demonstrating once and for all that Homo neanderthalensis deserves a distinctive identity of its own."