What makes humans unique? The nose probably isn't anyone's first answer to that question. Yet compared to the other primates (and earlier members of our family) we do have an unusual protruding nose. What's up with that?
One popular explanation for why we have such an unusual bogeyhole is that the nose is a natural sort of "air conditioning". The conditions in the nose cool or heat incoming air as needed. Since we're the only ape species to live in a range of environments where this would be an issue (others being restricted to the equator) it makes sense that we'd need to adapt to deal with the tricky air that we'd encounter elsewhere.
As well as explaining why our nose is different to other apes, this could also explain why there was some variation within the human family. Neanderthals tended to have bigger proboscis than us. Could this be because they lived in a cooler climate so needed better heating equipment?
Maybe not. New research reveals that - whilst our nasal region is pretty good at air conditioning - the shape of the nose itself doesn't have much to do with it. Our pointy nose appears to be pointless.
Modelling the nose
This revelation about our nostrils comes from research that chopped up primate noses in order to see how that changed their air conditioning ability. Fortunately for my stomach (and their ethics approval) they did this with virtual models.
The researchers CT scanned a variety of primates and humans. Based on this they built computer models of the whole nasal organ to see how air flows through it (and any air conditioning that happened during the process). Once they had this information they could mix up the nose models as much as they wanted to see if it had any impact on these factors.
The main change they were examining is the flow of air. In most primates, their flat nose means it goes straight into the nasal cavity. However, as air enters our schnozz it has to travel up and over. So they tried giving us a primate style horizontal air flow; and primates had a practice with a human-like up and over movement. All of this virtual plastic surgery and simulation revealed two rather interesting conclusions:
- The ultimate shape of the nose is pointless. The fact ours has given us a different type of air flow has no real impact on its ability to cool/heat that air as needed.
- The real factor involved in air conditioning is the length of the nasal cavity. Notably, humans have a larger nasal cavity. This would suggest that our face did evolve to help with air conditioning, just no the shape of the nose.
Of course, this isn't to say that the nose is definitely useless. It could have evolved for some alternate reason. Like sexual selection. But currently there's no real evidence for any reasons, so any such argument is just speculation at this time. As far as we can tell the nose is pointless.
Hybrid hunting
So, it would seem that our tiny trunk is relatively useless. At least, that's what the researchers conclude. They suggest that it's unusual shape might simply be a side-effect of other, more meaningful changes to the human face. Like perhaps the lengthening of the nasal cavity. But whilst the nose might not be that interesting from an evolutionary point of view, another group of researchers have found a rather good use for it: hunting down Neanderthal hybrids.
They were studying baboons. Specifically yellow and olive baboons. These two species have some overlapping territory in Central Africa. There, hybrids seem to be relatively common. Observations in the region identified several individuals that were definitely a mixture of the two species, and their specimens were collected after death. It was these specimens that were being re-examined by these scientists. They were specifically studying the whole nose organ as it was very different in both olive and yellow baboons. Quite similar to how it differs a lot between humans and Neanderthals.
This revealed that the hybrid nose was unique, like neither the olive or the yellow baboon. Based on this, they inferred that a similar situation might happen with any human/Neanderthal hybrids. Thus, finding fossils with a unique nose hole could indicate that they were actually hybrids of the two. Although, unfortunately they can't cite any examples of any fossils where this has actually happened. They also note that the human and baboon nose aren't exactly identical, so the same trend might not exist in both.
So is the nose back to being useless? Not quite.
This research into hybridisation is interesting because it shows that the merging of two species can produce unique traits. Like the unique nose seen in these baboon hybrids. Thus, these sorts of mixtures could be an evolutionary force. Currently, this force is thought to have been so rare that it wasn't evolutionarily significant. It seems humans and Neanderthal interbred on only a handful of occasions, for example.
But those few occasions could have been more important than we thought they were. As least, f=if we're as similar to baboons as our politicians indicate.
Summary
The human nose was thought to have evolved to help cool or heat up the air as needed. New research suggests it's actually useless, but could help us spot Neanderthal hybrids.
References
Eichel, K.A. and Ackermann, R.R., 2016. Variation in the nasal cavity of baboon hybrids with implications for late Pleistocene hominins. Journal of human evolution, 94, pp.134-145.
Nishimura, T., Mori, F., Hanida, S., Kumahata, K., Ishikawa, S., Samarat, K., Miyabe-Nishiwaki, T., Hayashi, M., Tomonaga, M., Suzuki, J. and Matsuzawa, T., 2016. Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo. PLoS Comput Biol, 12(3), p.e1004807.
Wolf, M., Naftali, S., Schroter, R.C. and Elad, D., 2004. Air-conditioning characteristics of the human nose. Journal of laryngology and otology, 118(2), pp.87-92.
Photo by herefordcat
