did not always lay five eggs a week, sheep did not always yield as much wool,
and horses were not always as strong and swift as they are now. Breeders
have made an artificial selection. The same applies to the vegetable kingdom.
You don’t plant bad potatoes if there are good seed potatoes available, and
you don’t waste time cutting wheat that yields no grain. Darwin pointed out
that no cows, no stalks of wheat, no dogs, and no finches are completely
alike. Nature produces an enormous breadth of variation. Even within the
same species, no two individuals are exactly alike. You probably experienced
that for yourself when you drank the blue liquid.”
“I’ll say.”
“So now Darwin had to ask himself: could a similar mechanism be at
work in nature too? Is it possible that nature makes a ‘natural selection’ as to
which individuals are to survive? And could such a selection over a very long
period of time create new species of flora and fauna?”
“I would guess the answer is yes.”
“Darwin could still not quite imagine how such a natural selection could
take place. But in October 1838, exactly two years after his return on the
Beagle, he chanced to come across a little book by the specialist in population
studies, Thomas Malthus. The book was called An Essay on the Principle of
Population. Malthus got the idea for this essay from Benjamin Franklin, the
American who invented the lightning conductor among other things. Franklin
had made the point that if there were no limiting factors in nature, one single
species of plant or animal would spread over the entire globe. But because
there are many species, they keep each other in balance.”
“I can see that.”
“Malthus developed this idea and applied it to the world’s population. He
believed that mankind’s ability to procreate is so great that there are always
more children born than can survive. Since the production of food can never
keep pace with the increase in population, he believed that huge numbers
were destined to succumb in the struggle for existence. Those who survived
to grow up— and perpetuate the race—would therefore be those who came
out best in the struggle for survival.”
“That sounds logical.”
“But this was actually the universal mechanism that Darwin had been
searching for. Here was the explanation of how evolution happens. It was due
to natural selection in the struggle for life, in which those that were best
adapted to their surroundings would survive and perpetuate the race. This
was the second theory which he proposed in The Origin of Species. He wrote:
The elephant is reckoned the slowest breeder of all known animals,’ but if it
had six young and survived to a hundred, ‘after a period of from 740 to 750
years there would be nearly nineteen million elephants alive, descended from
the first pair.’ “
“Not to mention all the thousands of cods’ eggs from a single cod.”
“Darwin further proposed that the struggle for survival is frequently
hardest among species that resemble each other the most. They have to fight
for the same food. There, the slightest advantage—that is to say, the
infinitesimal variation—truly comes into its own. The more bitter the struggle
for survival, the quicker will be the evolution of new species, so that only the
very best adapted will survive and the others will die out.”
“The less food there is and the bigger the brood, the quicker evolution