"the darker ones survived best."

　　"Yes, so now it wasn't long before they increased in number. From 1848 to 1948, the proportion of dark peppered moths increased from 1 to 99 percent in certain places. The environment had changed, and it was no longer an advantage to be light. On the contrary. The white 'losers' were weeded out with the help of the birds as soon as they appeared on the birch trunks. But then something significant happened again. A decrease in the use of coal and better filtering equipment in the factories has recently produced a cleaner environment."

　　"So now the birches are silver again?"

　　"And therefore the peppered moth is in the process of returning to its silvery color. This is what we call adaptation. It's a natural law."

　　"Yes, I see."

　　"But there are numerous examples of how man interferes in the environment."

　　"Like what?"

　　"For example, people have tried to eradicate pests with various pesticides. At first, this can produce excellent results. But when you spray a field or an orchard with pesticides, you actually cause a miniature ecocatastrophe for the pests you are trying to eradicate. Due to continual mutations, a type of pest develops that is resistant to the pesticide being used. Now these 'winners' have free play, so it becomes harder and harder to combat certain kinds of pest simply because of man's attempt to eradicate them. The most resistant variants are the ones that survive, of course."

　　"That's pretty scary."

　　"It certainly is food for thought. We also try to combat parasites in our own bodies in the form of bacteria."

　　"We use penicillin or other kinds of antibotic."

　　"Yes, and penicillin is also an ecocatastrophe for the little devils. However, as we continue to administer penicillin, we are making certain bacteria resistant, thereby cultivating a group of bacteria that is much harder to combat than it was before. We find we have to use stronger and stronger antibiotics, until . . ."

　　"Until they finally crawl out of our mouths? Maybe we ought to start shooting them?"

　　"That might be a tiny bit exaggerated. But it is clear that modern medicine has created a serious dilemma. The problem is not only that a single bacterium has become more virulent. In the past, there were many children who never survived——they succumbed to various diseases. Sometimes only the minority survived. But in a sense modern medicine has put natural selection out of commission. Something that has helped one individual over a serious illness can in the long run contribute to weakening the resistance of the whole human race to certain diseases. If we pay absolutely no attention to what is called hereditary hygiene, we could find ourselves facing a degeneration of the human race. Mankind's hereditary potential for re-sisting serious disease will be weakened."

　　"What a terrifying prospect!"

　　"But a real philosopher must not refrain from pointing out something 'terrifying' if he otherwise believes it to be true. So let us attempt another summary."

　　"Okay."

　　"You could say that life is one big lottery in which only the winning numbers are visible."

　　"What on earth do you mean?"

　　"Those that have lost in the struggle for existence have disappeared, you see. It takes many millions of years to select the winning numbers for each and every species of vegetable and animal on the earth. And the losing numbers——well, they only make one appearance. So there are no species of animal or vegetable in existence today that are not winning numbers in the great lottery of life."