Why Wouldn’t You Know – And Want To Know Why – Wombat Poo Is Cube Shaped?

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Having discussed politics already today time to turn to a subject less disgusting and more fragrant – wombat poo. The most notable feature of which is that it’s cube shaped, even near cubic. This not being one of the shapes we often see in nature and really not that often in ordure – but then I did say this wasn’t about politics, didn’t I? – flat splats and tubular being more common. The former because of water content, the latter intestinal.

But the universe not only contains its mysteries, it also has those who would unravel them:

A team of scientists claims to have unraveled one of the animal kingdom’s more peculiar mysteries: why wombat poop is cube-shaped.

The wombat, native to Australia, produces about 80 to 100 cubes of poop each night.

This is not just some happenstance of their diet, like finding that a radical change in our own leads to discomfort while astride the porcelain. There’s a purpose to this.

Why the pudgy marsupials might benefit from six-faced faeces is generally agreed upon: wombats mark their territorial borders with fragrant piles of poo and the larger the piles the better. With die-shaped dung, wombats boost the odds that their droppings, deposited near burrow entrances, prominent rocks, raised ground and logs, will not roll away. That, at least, is the thinking.

OK, there’s the advantage, now, how the how?

In wombats, the faeces changed from a liquid-like state into a solid state in the last 25% of the intestines – but then in the final 8% a varied elasticity of the walls meant the poop would take shape as separated cubes.

This, the scientists explain, resulted in 2cm (0.8in) cube-shaped poops unique to wombats and the natural world.

The marsupial then stacks the cubes – the higher the better so as to communicate with and attract other wombats.

Most informative we’ll all agree.

However, it’s important to note how this evolution stuff works. It is not true that wombat intestines changed so as to benefit them – producing the cube shaped poo they use to communicate and mark territory. That’s not the direction of evolution. Rather, the change is random, it’s the environment that then selects for fitness. Selecting by those more fit having more offspring that then go on to have offspring. Thus the order in which this happened. A random mutation led to the change in one or more wombat intestines. The – likely slightly more – cubic poo and its communication and marking possibilities leading to more offspring carrying that gene, they in turn benefit by having more offspring and the gene(s) spread through the population.

The evolutionary just so stories, as with this one about cubic wombat poo, are illuminating, but only if we get the order of events the right way around. Change first by random mutation, then selection, it’s never change in order to.