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Doctor Who: What would aliens really look like?

Updated Thursday, 14th November 2013

When it comes to aliens, are the makers of Doctor Who really lacking imagination?

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aliens baloons Copyrighted  image Icon Copyright: © Scmedlin | Dreamstime.com What would aliens really be like? Assuming there are any, of course. We’re inevitably prejudiced by what we already know, so you might think the makers of Doctor Who would inevitably lack imagination compared to what aliens might really be like. However nature answers this for us. Life evolves repeatedly to fill and re-fill very similar ecological niches, and surprise surprise the results look similar. This is the reason a dolphin looks like a fish, or a triceratops looks like a bull, or a marsupial wolf looks like a dog, or the darting around of shoals of fish look like the darting around of flocks of birds. Their shapes and functions are optimized by generations of evolution against similar external constraints. Experts in this area call this “convergent evolution”.

For this reason, my guess is that this sort of life is probably LESS diverse than the imaginations of the BBC. Some constraints will be different, such as the amount of oxygen in the air, which could have some general effect. Watch out in more oxygen-rich planets: spiders “breathe” through their skin, and what limits the size of invertebrates is how much oxygen they can take in through their skin for their body size, so more oxygen in the air means bigger spiders. This probably happened in Earth’s past, so nature did that experiment for us too (there’s a trip you might not want to make with a Tardis).

But there’s still a sense in which our imagination is limiting us: it’s in the nature of the life we’re thinking about. OK, if you find a big grazing animal, it’s probably going to look fairly similar no matter where you find it. But there are many more sorts of life. What about microscopic life? There are more bacteria cells in your own body than cells of you, existing symbiotically with you. Even your own cells wouldn’t work without a symbiotic relationship with mitochondria. Speaking of relationships, what about ant colonies – are they alive, independently of the individual ants? And this is just the natural world we know about.

We know little about the deep interiors of gas giant planets, very little indeed about the interiors of neutron stars, and next to nothing about any potential new forces that only dark matter particles could feel. Things could happen in these environments that bear no relation to human scales – they could be far too fast, or take millions or hundreds of millions of years, or be both astronomically vast and difficult to detect. Are any of these exotic substances and places suitable for a process like natural selection to operate on information propagating from generation to generation? More to the point, even if you were a Time Lord with a Tardis, would you recognise this life as life if you saw it?

 

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