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."
"Because only the best have survived."
"Yes, that's another way of saying it. And now, if you will kindly pass me the picture which that fellow--that zookeeper--brought us . . ."
Sophie passed the picture over to him. The picture of Noah's Ark covered one side of it. The other was devoted to a tree diagram of all the various species of animals. This was the side Alberto was now showing her.
"Our Darwinian Noah also brought us a sketch that shows the distribution of the various vegetable and animal species. You can see how the different species belong in the different groups, classes, and subkingdoms."
"Yes."
"Together with monkeys, man belongs to the so-called primates. Primates are mammals, and all mammals belong to the vertebrates, which again belong to the multi-cellular animals."
"It's almost like Aristotle."
"Yes, that's true. But the sketch illustrates not only the distribution of the different species today. It also tells something of the history of evolution. You can see, for example, that birds at some point parted from reptiles, and that reptiles at some point parted from amphibia, and that amphibia parted from fishes."
"Yes, it's very clear."
"Every time a line divides into two, it's because mutations have resulted in a new species. That is how, over the ages, the different classes and subkingdoms of animals arose. In actual fact there are more than a million animal species in the world today, and this million is only a fraction of the species that have at some time lived on the earth. You can see, for instance, that an animal group such as the Trilobita is totally extinct."
"And at the bottom are the monocellular animals."
"Some of these may not have changed in two billion years. You can also see that there is a line from these monocellular organisms to the vegetable kingdom. Because in all probability plants come from the same primal cell as animals."
"Yes, I see that. But there's something that puzzles me."
"Yes?"