New research sheds light on Neanderthals' distinctive features

Study appears to rule out theory that Neanderthals’ facial shape was adapted for a powerful bite

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3992Reconstructions of a Neanderthal man and woman at the Neanderthal museum in Mettmann, Germany. Photograph: Martin Meissner/AP

With their prominent noses, protruding faces and swept-back cheekbones, Neanderthals were nothing if not striking. Now researchers say they have unpicked why our big-browed cousins had such distinctive features.

Previous research has suggested a number of possible explanations for Neanderthals’ facial shape, including that it enabled a forceful bite with the front teeth – a theory based on their relatively large incisors and signs of tooth wear.

As well as the processing of food, it looks like they were using their teeth [for] gripping as a third hand, and that of course would put a lot of force on the front of the jawbone,” said Dr Chris Stringer, head of human origins at the Natural History Museum in London and a co-author of the new study.

But the study appears to rule out that theory, instead supporting other explanations for Neanderthals’ facial structure, including that it provided an efficient way to warm and moisten cold, dry air and move large volumes of air through the nasal passage. Such heavy breathing, the researchers say, could also be an adaptation to cold climates or prove a boon for an energetic lifestyle, noting that it is thought Neanderthals used up to 4,480 calories a day in finding food during the winter and keeping warm.

Writing in the journal Proceedings of the Royal Society B, Stringer and colleagues report how they came to their conclusions after exploring the similarities and differences between skulls of different species of human, based on virtual reconstructions from CT scans.

These digital forms were based on 11 skulls from our own species, Homo sapiens, including one Ice Age specimen; three from Neanderthals; and one from a member of another extinct human species, Homo heidelbergensis, dug up in Africa. In some cases further specimens were used to aid the digital reconstructions.

The team then ran computer simulations to look at various aspects of the biomechanics of bites, before carrying out another simulation using a subset of the skulls to model heat flow through the nasal passage.

The results reveal that Neanderthals do not appear to have had a particularly powerful bite. “In this study it found no significant difference between all three [species],” said Stringer, noting that in fact modern humans might even be slightly better adapted for a strong biting force.

A surprising result of our simulations was that modern humans can bite hard - and we do it using weaker jaw muscles. Turns out we modern humans are very efficient biters,” said Prof Stephen Wroe, lead author of the study from the University of New England, Australia.

But clear differences were found in the second study, with modern humans the most efficient at warming and humidifying air breathed in through the nose, followed by Neanderthals, which the team suggests shows adaptation to colder, drier climates than the Homo heidelbergensis specimen experienced.

The team found that Neanderthal nasal passages were about 29% larger than those of modern humans. But, they stress, size isn’t the only thing that matters for airflow. Indeed, by considering predicted nostril sizes, they found Neanderthals and to a lesser extent Homo heidelbergensis were both able to move air through their nasal passages at a greater rate than modern humans. That, say the researchers, could help to sustain an active lifestyle involving much huffing and puffing.

The calorific demands of Neanderthals were huge compared with ours – they were moving around a lot, they probably had less efficient clothing and therefore they are having to burn a lot more of their body fat to keep warm,” said Stringer, adding that heavy nasal breathing could also have been handy in a cold climate.

Stringer notes that while Neanderthals did not live in conditions as harsh as those experienced by the Inuit, they lived across a range of climates including those similar to the Mediterranean today and those far colder than modern Britain. “They are able to survive apparently in both those environments, and it will be the most severe ones that are pruning their morphology and adapting them,” he said.

Dr Matt Pope, a palaeolithic researcher at the UCL Institute of Archaeology, welcomed the research, noting that despite evidence showing similarities between Neanderthals and modern humans, anatomical differences are undeniable. “It is in part explaining these physical differences and I think that is really exciting,” he said. “We now need to read this again against the archeological evidence to see how [Neanderthals] are using their very powerful bodies, their very energetically demanding bodies, perhaps in different ways to how anatomically modern humans are using them.”