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What is evolution?

Updated Monday, 27th July 2009

Stephen Serjeant explains that survival of the fittest is about reproduction more than strength

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Most people think they know what evolution's all about - survival of the fittest, right? The strongest animals survive?

In fact that's not what it's about at all. 'Fittest' doesn't mean 'strongest', it means the best at making babies. Imagine a giant carnivorous monster that can't have babies, and compare it to bunnies that don't have strong defences but do reproduce like, er, bunnies.

A thousand years later, are you going to see bunnies or carnivorous monsters? Of course you're going to see the things that have reproduced, not the things that haven't.

Whales swim around with open mouths constantly scooping up defenceless plankton, but plankton is the evolutionary winner because it makes up for being eaten by reproducing very fast and making huge numbers of offspring. It's not about strength, it's about leaving descendents.

A rabbit on grass Copyrighted  image Icon Copyright:
A rabbit on grass.

It's also not about YOU either. It's not the survival of individuals at all. It's the survival of sets of genes, your DNA. If there's a trait that makes people better at making healthy babies that will grow up to reproduce themselves, that trait will get passed on, and slowly over the generations the individuals who have that trait will outnumber the ones that don't. Genes that hinder survival and reproduction are gradually lost. That's evolution in progress.

Individuals aren't central in evolution at all - they're just the way that DNA propagates down through time. There's a saying in evolution: a chicken is an egg's way of making another egg. The geneticist Steve Jones also once said "Yes, there is life after death - it is called children. We die but our genes don't."

Evolution also isn't about progress, just about being well adapted to your environment. If the environment changes the traits that made you 'fittest' in the old environment may not do so in the new one. Individuals with traits that give them an advantage in the new environment will start to leave more children, and so a different set of genes becomes dominant.

We like to think we're at the top of the evolutionary tree, and compare our intelligence to that of other animals. There's certainly a case for us being more intelligent, but what we're really doing is judging animals against what humans have specialised in. That's not fair on the animals. How would you fare in a swimming race against a dolphin? Who has the 'best' genes all depends on the environment!

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Find out more

Tim Halliday on natural selection and evolution
Video: Richard Dawkins on Charles Darwin
Video: Steve Jones on the work to decode DNA
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