ages in such a way that new species of finches evolved?”
“That was the conclusion he came to, wasn’t it?”
“Yes. Maybe that was where Darwin became a ‘Darwinist’—on the
Galapagos Islands. He also observed that the fauna there bore a strong
resemblance to many of the species he had seen in South America. Had God
once and for all really created all these animals slightly different from each
other—or had an evolution taken place? Increasingly, he began to doubt that
all species were immutable. But he still had no viable explanation as to how
such an evolution had occurred. But there was one more factor to indicate
that all the animals on earth might be related.”
“And what was that?”
“The development of the embryo in mammals. If you compare the
embryos of dogs, bats, rabbits, and humans at an early stage, they look so
alike that it is hard to tell the difference. You cannot distinguish a human
embryo from a rabbit embryo until a very late stage. Shouldn’t this indicate
that we are distant relatives?”
“But he had still no explanation of how evolution happened?”
“He pondered constantly on [yell’s theory of the minute changes that
could have great effect over a long period of time. But he could find no
explanation that would apply as a general principle. He was familiar with the
theory of the French zoologist Lamarck, who had shown that the different
species had developed the characteristics they needed. Giraffes, for example,
had developed long necks because for generations they had reached up for
leaves in the trees. Lamarck believed that the characteristics each individual
acquires through his own efforts are passed on to the next generation. But
this theory of the heredity of ‘acquired characteristics’ was rejected by Darwin
because Lamarck had no proof of his bold claims. However, Darwin was
beginning to pursue another, much more obvious line of thought. You could
almost say that the actual mechanism behind the evolution of species was
right in front of his very nose.”
“So what was it?”
“I would rather you worked the mechanism out for yourself. So I ask: If
you had three cows, but only enough fodder to keep two of them alive, what
would you do?”
“I suppose I’d have to slaughter one of them.”
“All right... which one would you slaughter?”
“I suppose I’d slaughter the one that gave the least milk.”
“Would you?”
“Yes, that’s logical, isn’t it?”
“That is exactly what mankind had done for thousands of years. But we
haven’t finished with your two cows yet. Suppose you wanted one of them to
calve. Which one would you choose?”
“The one that was the best milker. Then its calf would probably be a
good milker too.”
“You prefer good milkers to bad, then. Now there’s one more question. If
you were a hunter and you had two gundogs, but had to give up one of them,
which one would you keep?”
“The one that’s best at finding the kind of game I shoot, obviously.”
“Quite so, you would favor the better gundog. That’s exactly how people
have bred domestic animals for more than ten thousand years, Sophie. Hens