"Is it a similar advantage to have white skin if you live in northern countries?"
"Yes, otherwise everyone on earth would be dark-skinned. But white skin more easily forms sun vitamins, and that can be vital in areas with very little sun. Nowadays that is not so important because we can make sure we have enough sun vitamins in our diet. But nothing in nature is random. Everything is due to infinitesimal changes that have taken effect over countless generations."
"Actually, it"s quite fantastic to imagine."
"It is indeed. So far, then, we can sum up Darwin"s theory of evolution in a few sentences."
"Go ahead!"
"We can say that the "raw material" behind the evolution of life on earth was the continual variation of individuals within the same species, plus the large number of progeny, which meant that only a fraction of them survived, the actual "mechanism," or driving force, behind evolution was thus the natural selection in the struggle for survival. This selection ensured that the strongest, or the "fittest," survived."
"It seems as logical as a math sum. How was The Origin of Species received?"
"It was the cause of bitter controversies. The Church protested vehemently and the scientific world was sharply divided. That was not really so surprising. Darwin had, after all, distanced G.o.d a good way from the act of creation, although there were admittedly some who claimed it was surely greater to have created something with its own innate evolutionary potential than simply to create a fixed ent.i.ty."
Suddenly Sophie jumped up from her chair.
"Look out there!" she cried.
She pointed out of the window. Down by the lake a man and a woman were walking hand in hand. They were completely naked.
"That"s Adam and Eve," said Alberto. "They were gradually forced to throw in their lot with Little Red Rid-inghood and Alice in Wonderland. That"s why they have turned up here."
Sophie went to the window to watch them, but they soon disappeared among the trees.
"Because Darwin believed that mankind was descended from animals?"
"In 1871 Darwin published The Descent of Man, in which he drew attention to the great similarities between humans and animals, advancing the theory that men and anthropoid apes must at one time have evolved from the same progenitor. By this time the first fossil skulls of an extinct type of man had been found, first in the Rock of Gibraltar and some years later in Neanderthal in Germany. Strangely enough, there were fewer protests in T871 than in 1859, when Darwin published The Origin of Species. But man"s descent from animals had been implicit in the first book as well. And as I said, when Darwin died in 1882, he was buried with all the ceremony due to a pioneer of science."
"So in the end he found honor and dignity?"
"Eventually, yes. But not before he had been described as the most dangerous man in England."
"Holy Moses!"
" "Let us hope it is not true," wrote an upper-cla.s.s lady, "but if it is, let us hope it will not be generally known." A distinguished scientist expressed a similar thought: "An embarra.s.sing discovery, and the less said about it the better." "
"That was almost proof that man is related to the ostrich!"
"Good point. But that"s easy enough for us to say now. People were suddenly obliged to revise their whole approach to the Book of Genesis. The young writer John Ruskin put it like this: "If only the geologists would leave me alone. After each Bible verse I hear the blows of their hammers." "
"And the blows of the hammers were his doubts about the word of G.o.d?"
"That was presumably what he meant. Because it was more than the literal interpretation of the story of creation that toppled. The essence of Darwin"s theory was the utterly random variations which had finally produced Man. And what was more, Darwin had turned Marv into a product of something as unsentimental as the struggle for existence."
"Did Darwin have anything to say about how such random variations arose?"
"You"ve put your finger on the weakest point in his theory. Darwin had only the vaguest idea of heredity. Something happens in the crossing. A father and mother never get two identical offspring. There is always some slight difference. On the other hand it"s difficult to produce anything really new in that way. Moreover, there are plants and animals which reproduce by budding or by simple cell division. On the question of how the variations arise, Darwin"s theory has been supplemented by the so-called neo-Darwinism."
"What"s that?"
"All life and all reproduction is basically a matter of cell division. When a cell divides into two, two identical cells are produced with exactly the same hereditary factors. In cell division, then, we say a cell copies itself."
"Yes?"
"But occasionally, infinitesimal errors occur in the process, so that the copied cell is not exactly the same as the mother cell. In modern biological terms, this is a mutation. Mutations are either totally irrelevant, or they can lead to marked changes in the behavior of the individual. They can be directly harmful, and such "mutants" will be continually discarded from the large broods. Many diseases are in fact due to mutations. But sometimes a mutation can give an individual just that extra positive characteristic needed to hold its own in the struggle for existence."
"Like a longer neck, for instance?"
"Lamarck"s explanation of why the giraffe has such a long neck was that giraffes have always had to reach upwards. But according to Darwinism, no such inherited characteristic would be pa.s.sed on. Darwin believed that the giraffe"s long neck was the result of a variation. Neo-Darwinism supplemented this by showing a clear cause of just that particular variation."
"Mutations?"
"Yes. Absolutely random changes in hereditary factors supplied one of the giraffe"s ancestors with a slightly longer neck than average. When there was a limited supply of food, this could be vital enough. The giraffe that could reach up highest in the trees managed best. We can also imagine how some such "primal giraffes" evolved the ability to dig in the ground for food. Over a very long period of time, an animal species, now long extinct, could have divided itself into two species. We can take some more recent examples of the way natural selection can work."
"Yes, please."
"In Britain there is a certain species of b.u.t.terfly called the peppered moth, which lives on the trunks of silver birches. Back in the eighteenth century, most peppered moths were silvery gray. Can you guess why, Sophie?"
"So they weren"t so easy for hungry birds to spot."
"But from time to time, due to quite chance mutations, some darker ones were born. How do you think these darker variants fared?"
"They were easier to see, so they were more easily snapped up by hungry birds."
"Yes, because in that environment-where the birch trunks were silver-the darker hue was an unfavorable characteristic. So it was always the paler peppered moths that increased in number. But then something happened in that environment. In several places, the silvery trunks became blackened by industrial soot. What do you think happened to the peppered moths then?"
"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 antibiotic."
"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 succ.u.mbed 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 resisting 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 pa.s.s me the picture which that fellow-that zookeeper-brought us . . ."
Sophie pa.s.sed 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, cla.s.ses, 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 ill.u.s.trates 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 cla.s.ses 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?"
"Where did this first primal cell come from? Did Darwin have any answer to that?"
"I said, did I not, that he was a very cautious man. But as regards that question, he did permit himself to propose what one might call a qualified guess. He wrote: If (and O, what an if!) we could picture some hot little pool in which all manner of ammoniacal and phosphorous salts, light, heat, electricity and so forth were present, and that a protein compound were to be chemically formed in it, ready to undergo even more complicated changes ..."
"What then?"
"What Darwin was philosophizing on here was how the first living cell might have been formed out of inorganic matter. And again, he hit the nail right on the head. Scientists of today think the first primitive form of life arose in precisely the kind of "hot little pool" that Darwin pictured."
"Go on."
"That will have to suffice because we"re leaving Darwin now. We"re going to jump ahead to the most recent findings about the origins of life on earth."
"I"m rather apprehensive. Does anybody really know how life began?"
"Maybe not, but more and more pieces of the puzzle have fallen into place to form a picture of how it may have begun."
"Well?"
"Let us first establish that all life on earth-both animal and vegetable-is constructed of exactly the same substances. The simplest definition of life is that it is a substance which in a nutrient solution has the ability to subdivide itself into two identical parts. This process is governed by a substance we call DNA. By DNA we mean the chromosomes, or hereditary structures, that are found in all living cells. We also use the term DNA molecule, because DNA is in fact a complex molecule-or macro-molecule. The question is, then, how the first molecule arose."
"Yes?"
"The earth was formed when the solar system came into being 4.6 billion years ago. It began as a glowing ma.s.s which gradually cooled. This is where modern science believes life began between three and four billion years ago."
"It sounds totally improbable."
"Don"t say that before you have heard the rest. First of all, our planet was quite different from the way it looks today. Since there was no life, there was no oxygen in the atmosphere. Free oxygen was first formed by the photosynthesis of plants. And the fact that there was no oxygen is important. It is unlikely that life cells-which, again, can form DNA-could have arisen in an atmosphere containing oxygen."
"Why?"
"Because oxygen is strongly reactive. Long before complex molecules like DNA could be formed, the DNA molecular cells would be oxydized."
"Really."
"That is how we know for certain that no new life arises today, not even so much as a bacterium or a virus. All life on earth must be exactly the same age. An elephant has just as long a family tree as the smallest bacterium. You could almost say that an elephant-or a human being- is in reality a single coherent colony of monocellular creatures. Because each cell in our body carries the same hereditary material. The whole recipe of who we are lies hidden in each tiny cell."
"That"s an odd thought."
"One of life"s great mysteries is that the cells of a multicellular animal have the ability to specialize their function in spite of the fact that not all the different hereditary characteristics are active in all the cells. Some of these characteristics-or genes-are "activated" and others are "deactivated." A liver cell does not produce the same proteins as a nerve cell or a skin cell. But all three types of cell have the same DMA molecule, which contains the whole recipe for the organism in question.
"Since there was no oxygen in the atmosphere, there was no protective ozone layer around the earth. That means there was nothing to stop the radiation from the cosmos. This is also significant because this radiation was probably instrumental in forming the first complex molecule. Cosmic radiation of this nature was the actual energy which caused the various chemical substances on the earth to start combining into a complicated macro-molecule."
"Okay."
"Let me recapitulate: Before such complex molecules, of which all life consists, can be formed, at least two conditions must be present: there must be no oxygen in the atmosphere, and there must be access for cosmic radiation."
"I get it."
"In this "hot little pool"-or primal soup, as it is often called by modern scientists-there was once formed a gigantically complicated macromolecule, which had the wondrous property of being able to subdivide itself into two identical parts. And so the long evolutionary process began, Sophie. If we simplify it a bit, we can say that we are now talking of the first hereditary material, the first DNA or the first living cell. It subdivided itself again and again-but from the very first stage, trans.m.u.tation was occurring. After aeons of time, one of these monocellular organisms connected with a more complicated multicel-lular organism. Thus the photosynthesis of plants also began, and in that way the atmosphere came to contain oxygen. This had two results: first, the atmosphere permitted the evolution of animals that could breathe with the aid of lungs. Secondly, the atmosphere protected life from the harmful cosmic radiation. Strangely enough, this radiation, which was probably a vital "spark" in the formation of the first cell, is also harmful to all forms of life."
"But the atmosphere can"t have been formed overnight. How did the earliest forms of life manage?"
"Life began in the primal "seas"-which are what we mean by primal soup. There it could live protected from the harmful rays. Not until much later, when life in the oceans had formed an atmosphere, did the first amphibians crawl out onto land. The rest is what we have already talked about. And here we are, sitting in a hut in the woods, looking back on a process that has taken three or four billion years. And in us, this long process has finally become aware of itself."