Useless Bits of Body

By: Dr Andrew Impey

Chinese food - my favourite. I'm particularly partial to spare ribs, although I have often wondered why certain animals have bits which are considered "spare."

It is often misquoted that women have one extra rib compared to men, a fallacy which is no doubt biblical in origin. Anatomically, both men and women have twelve pairs of ribs- the lowest two pairs, known as "floating ribs", are only connected to the spinal column and not the rest of the rib cage. Nevertheless, there is nothing spare about them.

While most of the ribs provide protection to the organs contained within the chest, such as the heart and lungs, the floating ribs help prevent damage occurring in the stomach, spleen and kidneys.

Moving on to other spare parts of the body, I can proudly declare that I do not have man-boobs (or, scientifically speaking, gynecomastia). Having said that, I do have nipples and even a little bit of breast tissue. But why? What do I need them for? It turns out that I used to be a woman.

In fact, we all start out life using a female foetal "template" up until about 14 weeks, after which us blokes begin producing hormones such as testosterone. By that time we've already developed nipples.

Now, ear lobes, wisdom teeth, the appendix and the coccyx "tailbone". What use are they? What you've got to remember is: just because they are useless now doesn't mean that they were useless to our ancestors. Wisdom teeth, for instance, were useful in replacing any pearly whites knocked out during a fight with a rival caveman. And the appendix, which might now be considered a surgical excuse for a few weeks off work, used to contain bacteria capable of digesting plant matter. It still serves this purpose in some herbivores to this very day.

Here's a really interesting one: nostrils. Why do we have two of them? Surely we could breathe in more air in a single breath if we had just one, large nasal orifice (a "monostril", perhaps)? The human body tends to be bilaterally symmetrical: we have two eyes, giving us binocular vision, and two ears, providing us with stereoscopic sound. So does having two nostrils allow us to triangulate the source of a particular pong?

Seemingly not. We only breathe through one nostril at a time (try it for yourself). At the time of writing this article, my left nostril is doing all the hard work although "righty" will soon take over, as the human "nasal cycle" causes my nostrils to swap jobs every few hours.

During the nasal cycle, one nostril experiences a swelling as blood vessels engorge, allowing less air to flow through the shrunken nasal cavity. The swelling is caused by erectile tissue, identical to that found "down under." So, does taking a Viagra tablet worsen one's sense of smell? That's a question yet to be answered. (I appreciate that if you've just taken a Viagra tablet, going around smelling things is probably the last thing on your mind).

Even though it appears that only one nostril is doing its job at any one time, it is widely believed (but not proven) that both nostrils are actually working on different smells to provide us with the ability to recognise a broad spectrum of stinks.

Smells come in two forms: odour chemicals that dissolve quickly in mucus, and those that dissolve slowly. By breathing in air at different rates through our different nostrils, we are providing the chemicals with varying amounts of time to dissolve in the snot before being detected by the olfactory cells (what are olfactory cells?). The "unblocked" nostril deals with the fast dissolving chemicals while the swollen, seemingly redundant nostril handles the slow dissolving odours.

Now I don't care which nostril it's coming through, but I'm definitely smelling spare ribs. I'm off down the Chinese.

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Andy worked for four years studying ducks (no stop laughing, he really did). He went into his PhD thinking he was going to save the world (albeit from ducks) and now spends him time lovingly preening Null Hypothesis, the Journal of Unlikely Science!

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