this theory alone could not explain why Darwin found the remains of sea
creatures high up in the Andes. But Darwin always remembered that tiny
gradual changes could result in dramatic alterations if they were given
sufficient time.”
“I suppose he thought the same explanation could be used for the
evolution of animals.”
“Yes, that was his thought. But as I said before, Darwin was a cautious
man. He posed questions long before he ventured to answer them. In that
sense he used the same method as all true philosophers: it is important to ask
but there is no haste to provide the answer.”
“Yes, I see.”
“A decisive factor in Lyell’s theory was the age of the earth. In Darwin’s
time, it was widely believed that about 6,000 years had elapsed since God
created the earth. That figure had been arrived at by counting the generations
since Adam and Eve.”
“How naive!”
“Well, it’s easy to be wise after the event. Darwin figured the age of the
earth to be 300 million years. Because one thing, at least, was clear: neither
Lyell’s theory of gradual geological evolution nor Darwin’s own theory of
evolution had any validity unless one reckoned with tremendously long
periods of time.”
“How old is the earth?”
“Today we know that the earth is 4.6 billion years old.”
“Wow!”
“Up to now, we have looked at one of Darwin’s arguments for biological
evolution, namely, the stratified deposits of fossils in various layers of rock.
Another argument was the geographic distribution of living species. This was
where Darwin’s scientific voyage could contribute new and extremely
comprehensive data. He had seen with his own eyes that the individuals of a
single species of animal within the same region could differ from each other in
only the minutest detail. He made some very interesting observations on the
Galapagos Islands, west of Ecuador, in particular.”
“Tell me about them.”
“The Galapagos Islands are a compact group of volcanic islands. There
were therefore no great differences in the plant and animal life there. But
Darwin was interested in the tiny differences. On all the islands, he came
across giant tortoises that were slightly different from one island to another.
Had God really created a separate race of tortoises for each and every
island?”
“It’s doubtful.”
“Darwin’s observations of bird life on the Galapagos were even more
striking. The Galapagos finches were clearly varied from island to island,
especially as regards the shape of the beak. Darwin demonstrated that these
variations were closely linked to the way the finches found their food on the
different islands. The ground finches with steeply profiled beaks lived on pine
cone seeds, the little warbler finches lived on insects, and the tree finches
lived on termites extracted from bark and branches ... Each and every one of
the species had a beak that was perfectly adapted to its own food intake.
Could all these finches be descended from one and the same species? And
had the finches adapted to their surroundings on the different islands over the