Charles Darwin and the Tree of Life Page #3

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So maybe, over the vastness

of geological time,

and particularly if species were

invading new environments,

those changes would amount

to very radical changes indeed.

Darwin drew a sketch in one

of his notebooks to illustrate his idea,

showing how a single ancestral species

might give rise

to several different ones,

and then wrote above it a tentative,

"I think".

Now he had to prove his theory.

And he spent years gathering

abundant and convincing evidence.

He was an extraordinary letter writer.

He wrote as many as a dozen

letters a day

to scientists and naturalists

all over the world.

He also realised that when people had

first started domesticating animals

they had been doing experiments for him

for centuries.

All domestic dogs are descended from

a single ancestral species, the wolf.

Dog breeders select those pups

that have the characteristics

that happen to please them.

Nature, of course,

selects those young animals

that are best suited

to a particular environment.

But the process is essentially the same.

And in both cases,

it has produced astonishing variety.

In effect,

many of these different breeds

could be considered different species,

because they do not, indeed,

they cannot interbreed.

For purely mechanical reasons,

there's no way in which a Pekingese

can mate with a Great Dane.

Of course, it's true that,

if you used artificial insemination,

you could get crosses between

almost any of these breeds.

but that's because human beings

have been selecting between dogs

for only a few centuries.

Nature has been selecting

between animals for millions of years,

tens of millions,

even hundreds of millions of years.

So what might have started out

as we would consider to be breeds,

have now become so different

they are species.

Darwin, sitting in Down House,

wrote to pigeon fanciers

and rabbit breeders

asking all kinds of detailed questions

about their methods and results.

He himself, being a country gentleman

and running an estate,

knew about breeding horses

and sheep and cattle.

He also conducted careful experiments

with plants in his greenhouse.

But Darwin knew that the idea

that species could appear

without divine intervention

would appall society in general.

And it was also contrary to the beliefs

of his wife, Emma,

who was a devout Christian.

Perhaps for that reason, he was keen to

keep the focus of his work scientific.

He made a point of not being drawn

in public about his religious beliefs.

But in the latter part of his life

he withdrew from attending church.

On Sundays, he would escort Emma

and the children here

to the parish church in Down,

but while they went into the service,

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