The philosopher Daniel Dennett

described Charles Darwin's theory of evolution, Darwinism,

as "the single best idea anyone has ever had".

It certainly was a brilliant one,

though Darwin wasn't the only one to come up with it.

The naturalist and explorer Alfred Russel Wallace

put forward a very similar explanation of the biological data

independently of him at around the same time.

But once Darwin published his book, On The Origin Of Species, in 1859,

the theory of evolution was ever-after linked with his name.

It was a radical idea

because, although Darwin didn't spell this out,

people soon realised it entailed the view that human beings

were just another species in the animal kingdom

and shared a common ancestor with apes.

For Victorian England, this was quite a bombshell.

As a young man,

Darwin had spent five years as a naturalist on a round the world trip

aboard HMS Beagle.

He'd gradually come to realise that species change over time -

they evolve.

Imagine you're a finch on a Galapagos island.

There are lots of plants with seeds, but not much else to eat.

Your bill is a good shape for cracking them open.

Lucky you.

That's probably just the result of a variation you find within a species.

You happen to have a beak that allows you to eat seeds.

Others aren't so fortunate.

You survive and reproduce,

and pass that trait on to some of your offspring.

The offspring that have beaks like yours flourish.

The same thing happens in the next generation.

Gradually, over many thousands of years,

the finches on this island that survive

become better adapted to the available foodstuff.

Your type of beak predominates.

On another island, the main diet is prickly pear,

and the finches that survive and flourish there

have very different shaped beaks from yours.

Not only do members of a species change as a result of such evolution,

but also entirely new species emerge.

Today's Darwinism

is rather different from Charles Darwin's Darwinism though.

We now have a much better understanding

of the biology of heredity than he did.

Darwinism today is a powerful combination

of Darwin's general theory with modern genetics.

Darwinism is central to understanding how we came to be what we are.

It's possibly the most important ism yet.

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