Monday, 28 March 2016

Unintelligent Design - As Plain As The Nose On Your Face!

PLOS Computational Biology: Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo

Don't get me wrong! The human face is beautiful - to another human! Who could look at a human face and see it as ugly?

Well, of course, we're genetically 'programmed' to be attracted to an 'attractive' face. That's why we define it as attractive! But looked at objectively from, say, the point of view of the proverbial space alien studying life on Earth, the human face is surely one of the strangest in the mammalian order. It is rotated down through ninety degrees so that it still points forward even though our spine now points upwards and not forwards like most other mammals.

The muzzle, which puts the mouth in front of everything else in most mammals, is receded backwards in humans so that we have a chin sticking out for no apparent reason. Take a profile of a human face and draw a line down the ridge of the nose so it curves around naturally to the chin, and what do you see? You see the profile of a monkey or an ape. In fact, you see the profile of something resembling our pre-hominid ancestors, the Australopithecines.

What has happened as our face evolved is that the facial bones became reduced and the mandible and maxilla receded. No-one is really sure why this happened as we diverged from our hominin ancestors and our cranium enlarged to allow for a larger brain. In some ways we resemble a neotenous ape with retained juvenile features. But one of the strangest things is what this did to our nose. We have been left with this rather strange triangular fleshy thing sticking out of the front of our faces.

Next time you are in a group of people, try looking at their noses sticking out of their faces and pointing around as they talk and look around them. You'll be hard-pressed not to laugh!

Now a team of scientists have studied the flow of air through the human nose and have found it doesn't even seem to perform one of the important functions it has in other mammals, including our closest relatives. It doesn't even warm and humidify (air-condition) the air we breathe into our lungs, yet having air of the right temperature and humidity delivered to our lungs and respiratory piping is considered to be essential over the longer term.

We are flat-faced hominins with an external nose that protrudes from the face. This feature was derived in the genus Homo, along with facial flattening and reorientation to form a high nasal cavity. The nasal passage conditions the inhaled air in terms of temperature and humidity to match the conditions required in the lung, and its anatomical variation is believed to be evolutionarily sensitive to the ambient atmospheric conditions of a given habitat. In this study, we used computational fluid dynamics (CFD) with three-dimensional topology models of the nasal passage under the same simulation conditions, to investigate air-conditioning performance in humans, chimpanzees, and macaques. The CFD simulation showed a horizontal straight flow of inhaled air in chimpanzees and macaques, contrasting with the upward and curved flow in humans. The inhaled air is conditioned poorly in humans compared with nonhuman primates. Virtual modifications to the human external nose topology, in which the nasal vestibule and valve are modified to resemble those of chimpanzees, change the airflow to be horizontal, but have little influence on the air-conditioning performance in humans. These findings suggest that morphological variation of the nasal passage topology was only weakly sensitive to the ambient atmosphere conditions; rather, the high nasal cavity in humans was formed simply by evolutionary facial reorganization in the divergence of Homo from the other hominin lineages, impairing the air-conditioning performance. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in the flat-faced Homo. Thus, the air-conditioning faculty in the nasal passages was probably impaired in early Homo members, although they have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved “Out of Africa” to explore the more severe climates of Eurasia.

Author Summary
This is the first investigation of nasal air conditioning in nonhuman hominoids based on computational fluid dynamics with digital topological models of the nasal passage made using medical imaging. Our comparative results of humans, chimpanzees, and macaques show that the inhaled air is conditioned poorly in humans compared with nonhuman primates. We also show that our protruding external nose has little effect on improving air conditioning. The nasal anatomy in Homo was weakly sensitive to the ambient atmosphere conditions in evolution, but was formed passively by facial reorganization in this genus. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in flat-faced Homo. Thus, despite an impaired air-conditioning conformation in the nasal passages, Homo members must have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved “Out of Africa” in the Early Pleistocene to explore the more severe climates and ecological environments of Eurasia.

So it looks like we gave up using our noses as our air-conditioning system but relied instead on a lengthened pharynx. This gave us the flexibility to adapt to different climates and eventually move out of Africa altogether. Although the authors don't mention it, a lengthened pharynx also made sophisticated speech possible. This allowed us to communicate knowledge and information with others, and this in turn enabled us to use our expanding brain.

The mystery is, from an intelligent (sic) design point of view which denies evolution and so can't regard anything as vestigial, why a next-to-useless nose was designed and placed on the human face in the first place. It has turbinate bones, a mucous lining and a good blood supply, all apparently to help with warming and humidification, then the airflow is all wrong so it doesn't work very well! For a piece of design this would mean the designer is stupid and behaves like a planner without a plan - unless it just has a sense of humour and likes looking at faces with a useless triangle of flesh sticking out the front.

Yes I know the "We can't know the mind of the creator!" argument will be trotted out as the usual default response to hard questions, but that just illustrates how useless intelligent (sic) design is as a scientific tool for explaining things. "It's just a mystery!" is not a useful scientific conclusion! In fact it isn't a scientific conclusion at all; it's a childish one.

As you would expect, a vestigial human nose isn't a problem for evolution which predicts vestigial organs and structures. Evolution as a scientific tool doesn't need to fall back on default childish 'mystery' conclusions because it deals with real-world things.

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1 comment :

  1. One might also wonder why a creator would not only give humans a poorly-functioning nasal cavity, but give the other primates ones that worked better. Claims of an intelligent designer would have to explain why that designer would take more care with the design of a baboon than of a human, at least in this one area.

    But I suspect any creationists reading this are just thinking "Hey, why does she keep calling me a flat-faced homo?"


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