Neanderthals may have been our closest evolutionary ancestors, but they had at least one feature that alway set them apart from early humans: their incredibly large noses. But just why Neanderthals had such huge noses is an enduring evolutionary mystery.

Neanderthals lived during some of the most extreme climatic conditions in recent history, as they eked out an existence in a Europe covered in glaciers. Paleontologists had long assumed that Neanderthal features evolved to cope with the cold, but that doesn't make explain the nose. Both animals and humans who live in colder climes tend to have narrower, longer noses, because a big broad nose, like that of the Neanderthal, would lose huge amounts of heat.

The best theory to explain this apparent paradox is that Neanderthals had absolutely gigantic sinuses inside the noses. These might have warmed up the cold air entering the nose and allowed the lungs to get access to some non-frigid air. That's one theory. But another argues the sinuses were actually unusually small and did the exact opposite, helping to expel excess heat and preventing outbreaks of cold sweats.

Paleoanthropologist Todd Rae explains just how much a mystery this all is and how little we really know: "The $64,000 question is what sinuses do - that is, what is their biological function. Scientists have been arguing over that for hundreds of years. There are dozens of suggestions for what they may do for the animals that have them, including adding resonance to the voice and acting as flotation devices!"

To figure out the answer, Rae and his fellow researchers used X-rays and CT scans to peer inside the Neanderthal nose. They discovered that Neanderthal sinuses were neither very big or very small, which seems to disprove both theories. It leaves paleontologists with one last possible solution, although it's not exactly an elegant answer. Maybe Neanderthals had big noses just because, a random fluke of evolution and nothing more. It's not an amazing answer, but it seems to be the only one supported by the available facts.

UC Davis paleoanthropologist Tim Weaver says the results of the research appear sound, although it's important to keep examining what made humans and Neanderthals different:

"I would agree with their overall conclusion that the differences between Neanderthals and modern human faces do not appear in general to be adaptations to extreme cold climates. That doesn't mean that smaller features might not be shaped by cold climate. The projection of the nose of Neanderthals is very pronounced, and we see that characteristic in present-day humans who have ancestry in cold climates. Whether that's due to cold climate is unclear, but it's at least consistent. One of the things that's really fascinating about Neanderthals is that they are perhaps the most closely related species to humans that have ever lived, and in that way can help us really understand the evolutionary forces that shaped us."

[via LiveScience]