Charles Darwin and the Tree of Life Page #2

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he sent to Richard Owen.

Owen was one of the most brilliant

zoologists of his time.

He was the first to recognise dinosaurs,

and indeed had invented their very name.

And he would later become

the creator and first director

of the Natural History Museum in London.

Many of the specimens

that Darwin collected

are still preserved and treasured here

among the 70 million other specimens

housed in the museum that Owen founded.

And here is one of them.

It's obviously the lower jaw

of some great animal,

and when Darwin discovered it, it had

bits of skin and hair attached to it

so at first it was thought to be the

remains of some unknown living species.

But now we know that it is a species

that was extinct for some 10,000 years,

a giant ground sloth.

Owen examined it in great detail

and eventually described it and

gave it the name of Mylodon darwinii

in honour of its discoverer.

But that mutual respect

between two great men of science

was not to last.

Soon after his return from his voyage,

Darwin made his home here in Down House

in Kent.

Here, he wrote an account of his travels

and worked on detailed

scientific treatises

about corals and barnacles and the

geology and fossils of South America.

But he also pondered deeply

on what he had seen in the Galapagos

and elsewhere.

Maybe species were not fixed.

Every day, he took a walk

in this small spinney

that he had planted

at the end of his garden.

And it was here that he came to ponder

on the problems of natural history

including that mystery of mysteries:

how could one species turn into another?

He noted that most, if not all, animals

produce many more young

than live to breed themselves.

This female blue tit, for example,

may well lay a dozen eggs a year,

perhaps 50 or so in her lifetime.

Yet only two of her chicks need to

survive and breed themselves

to maintain the numbers

of the blue tit population.

Those survivors, of course,

are likely to be the healthiest

and best-suited

to their particular environment.

Their characteristics

are then inherited

so perhaps over many generations,

and particularly if there are

environmental changes,

species may well change.

Only the fittest survive.

And that was the key.

He called the process natural selection.

(BIRDSONG)

That would explain the differences

that he had noted in the finches

that he had brought back

from the Galapagos.

They were very similar

except for their beaks.

This one has a very thin, delicate beak,

which it uses to catch insects.

This one, on the other hand,

which came from an environment

where there were a lot of nuts,

has a big, heavy beak,

which enables it to crack them.

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