Sophie and Alberto went inside and sat down again. Sophie began to look at the picture, but before she had a chance to study it, Alberto took it from her with an authoritative grasp.
"We"ll concentrate on the broad outlines first."
"Okay, okay."
"I forgot to mention that Marx lived the last 34 years of his life in London. He moved there in 1849 and died in 1883. All that time Charles Darwin was living just outside London. He died in 1882 and was buried with great pomp and ceremony in Westminster Abbey as one of England"s distinguished sons. So Marx and Darwin"s paths crossed, but not only in time and s.p.a.ce. Marx wanted to dedicate the English edition of his greatest work, Capital, to Darwin, but Darwin declined the honor. When Marx died the year after Darwin, his friend Friedrich En-gels said: As Darwin discovered the theory of organic evolution, so Marx discovered the theory of mankind"s historical evolution."
"I see."
"Another great thinker who was to link his work to Darwin was the psychologist Sigmund Freud. He also lived his last years in London. Freud said that both Darwin"s theory of evolution and his own psychoa.n.a.lysis had resulted in an affront to mankind"s naive egoism."
"That was a lot of names at one time. Are we talking about Marx, Darwin, or Freud?"
"In a broader sense we can talk about a naturalistic current from the middle of the nineteenth century until quite far into our own. By "naturalistic" we mean a sense of reality that accepts no other reality than nature and the sensory world. A naturalist therefore also considers mankind to be part of nature. A naturalistic scientist will exclusively rely on natural phenomena-not on either rationalistic suppositions or any form of divine revelation."
"And that applies to Marx, Darwin, and Freud?"
"Absolutely. The key words from the middle of the last century were nature, environment, history, evolution, and growth. Marx had pointed out that human ideologies were a product of the basis of society. Darwin showed that mankind was the result of a slow biological evolution, and Freud"s studies of the unconscious revealed that people"s actions were often the result of "animal" urges or instincts."
"I think I understand more or less what you mean by naturalistic, but isn"t it best we talk about one person at a time?"
"We"ll talk about Darwin, Sophie. You may recall that the pre-Socratics looked for natural explanations of the processes of nature. In the same way that they had to distance themselves from ancient mythological explanations, Darwin had to distance himself from the church"s view of the creation of man and beast."
"But was he a real philosopher?"
"Darwin was a biologist and a natural scientist. But he was also the scientist of recent times who has most openly challenged the Biblical view of man"s place in Creation."
"So you"ll have to say something about Darwin"s theory of evolution."
"Let"s begin with Darwin the man. He was born in the little town of Shrewsbury in 1809. His father, Dr. Robert Darwin, was a renowned local physician, and very strict about his son"s upbringing. When Charles was a pupil at the local grammar school, his headmaster described him as a boy who was always flying around, fooling about with stuff and nonsense, and never doing a stroke of anything that was the slightest bit useful. By "useful," the headmaster meant cramming Greek and Latin verbs. By "flying around," he was referring among other things to the fact that Charles clambered around collecting beetles of all kinds."
"I"ll bet he came to regret those words."
"When he subsequently studied theology, Charles was far more interested in bird-watching and collecting insects, so he did not get very good grades in theology. But while he was still at college, he gained himself a reputation as a natural scientist, not least due to his interest in geology, which was perhaps the most expansive science of the day. As soon as he had graduated in theology at Cambridge in April 1831, he went to North Wales to study rock formations and to search for fossils. In August of the same year, when he was barely twenty-two years old, he received a letter which was to determine the course of his whole life . . ."
"What was the letter about?"
"It was from his friend and teacher, John Steven Hens-low. He wrote: "I have been requested to ... recommend a naturalist to go as companion to Captain Fitzroy, who has been commissioned by the government to survey the southern coasts of South America. I have stated that I consider you to be the best qualified person I know of who is likely to undertake such a situation. As far as the financial side of it is concerned, I have no notion. The voyage is to last two years ... " "
"How can you remember all that by heart?"
"A bagatelle, Sophie."
"And what did he answer?"
"He wished ardently to grasp the chance, but in those days young men did nothing without their parents" consent. After much persuasion, his father finally agreed- and it was he who financed his son"s voyage. As far as the "financial side" went, it was conspicuous by its absence."
"Oh."
"The ship was the naval vessel HMS Beagle. It sailed from Plymouth on December 27, 1831, bound for South America, and it did not return until October of 1836. The two years became five and the voyage to South America turned into a voyage round the world. And now we come to one of the most important voyages of discovery in recent times."
"They sailed all the way round the world?"
"Yes, quite literally. From South America they sailed on across the Pacific to New Zealand, Australia, and South Africa. Then they sailed back to South America before setting sail for England. Darwin wrote that the voyage on board the Beagle was without doubt the most significant event in his life."
"It couldn"t have been easy to be a naturalist at sea."
"For the first years, the Beagle sailed up and down the coast of South America. This gave Darwin plenty of opportunity to familiarize himself with the continent, also inland. The expedition"s many forays into the Galapagos Islands in the Pacific west of South America were of decisive significance as well. He was able to collect and send to England vast amounts of material. However, he kept his reflections on nature and the evolution of life to himself. When he returned home at the age of twenty-seven, he found himself renowned as a scientist. At that point he had an inwardly clear picture of what was to become his theory of evolution. But he did not publish his main work until many years after his return, for Darwin was a cautious man-as is fitting for a scientist."
"What was his main work?"
"Well, there were several, actually. But the book-which gave rise to the most heated debate in England was The Origin of Species, published in 1859. Its full t.i.tle was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. The long t.i.tle is actually a complete resume of Darwin"s theory."
"He certainly packed a lot into one t.i.tle."
"But let"s take it piece by piece. In The Origin of Species, Darwin advanced two theories or main theses: first, he proposed that all existing vegetable and animal forms were descended from earlier, more primitive forms by way of a biological evolution. Secondly, that evolution was the result of natural selection."
"The survival of the fittest, right?"
"That"s right, but let us first concentrate on the idea of evolution. This, in itself, was not all that original. The idea of biological evolution began to be widely accepted in some circles as early as 1800. The leading spokesman for this idea was the French zoologist Lamarck. Even before him, Darwin"s own grandfather, Erasmus Darwin, had suggested that plants and animals had evolved from some few primitive species. But none of them had come up with an acceptable explanation as to how this evolution happened. They were therefore not considered by churchmen to be any great threat."
"But Darwin was?"
"Yes, indeed, and not without reason. Both in ecclesiastic and scientific circles, the Biblical doctrine of the immutability of all vegetable and animal species was strictly adhered to. Each and every form of animal life had been created separately once and for all. This Christian view was moreover in harmony with the teachings of Plato and Aristotle."
"How so?"
"Plato"s theory of ideas presupposed that all animal species were immutable because they were made after patterns of eternal ideas or forms. The immutability of animal species was also one of the cornerstones of Aristotle"s philosophy. But in Darwin"s time there were a number of observations and finds which were putting traditional beliefs to the test."
"What kind of observations and finds were they?"
"Well, to begin with an increasing number of fossils were being dug out. There were also finds of large fossil bones from extinct animals. Darwin himself was puzzled to find traces of sea creatures far inland. In South America he made similar discoveries high up in the mountains of the Andes. What is a sea creature doing in the Andes, Sophie? Can you tell me that?"
"No."
"Some believed that they had just been thrown away there by humans or animals. Others believed that G.o.d had created these fossils and traces of sea creatures to lead the unG.o.dly astray."
"But what did scientists believe?"
"Most geologists swore to a "catastrophe theory/ according to which the earth had been subjected to gigantic floods, earthquakes, and other catastrophes that had destroyed all life. We read of one of these in the Bible-the Flood and Noah"s Ark. After each catastrophe, G.o.d renewed life on earth by creating new-and more perfect- plants and animals."
"So the fossils were imprints of earlier life forms that had been wiped out after these gigantic catastrophes?"
"Precisely. For example, it was thought that fossils were imprints of animals that had failed to get into the Ark. But when Darwin set sail on the Beagle, he had with him the first volume of the English biologist Sir Charles Lyell"s Principles of Geology. Lyell held that the present geology of the earth, with its mountains and valleys, was the result of an interminably long and gradual evolution. His point was that even quite small changes could cause huge geological upheavals, considering the aeons of time that have elapsed."
"What kind of changes was he thinking of?"
"He was thinking of the same forces that prevail today: wind and weather, melting ice, earthquakes, and elevations of the ground level. You"ve heard the saying about a drop of water wearing away a stone-not by brute force, but by continuous dripping. Lyell believed that similar tiny and gradual changes over the ages could alter the face of nature completely. However, this theory alone could not explain why Darwin found the remains of sea creatures high up in the Andes. But Darwin always remembered that tiny gradual changes could result in dramatic alterations if they were given sufficient time."
"I suppose he thought the same explanation could be used for the evolution of animals."
"Yes, that was his thought. But as I said before, Darwin was a cautious man. He posed questions long before he ventured to answer them. In that sense he used the same method as all true philosophers: it is important to ask but there is no haste to provide the answer."
"Yes, I see."
"A decisive factor in Lyell"s theory was the age of the earth. In Darwin"s time, it was widely believed that about 6,000 years had elapsed since G.o.d created the earth. That figure had been arrived at by counting the generations since Adam and Eve."
"How naive!"
"Well, it"s easy to be wise after the event. Darwin figured the age of the earth to be 300 million years. Because one thing, at least, was clear: neither Lyell"s theory of gradual geological evolution nor Darwin"s own theory of evolution had any validity unless one reckoned with tremendously long periods of time."
"How old is the earth?"
"Today we know that the earth is 4.6 billion years old."
"Wow!"
"Up to now, we have looked at one of Darwin"s arguments for biological evolution, namely, the stratified deposits of fossils in various layers of rock. Another argument was the geographic distribution of living species. This was where Darwin"s scientific voyage could contribute new and extremely comprehensive data. He had seen with his own eyes that the individuals of a single species of animal within the same region could differ from each other in only the minutest detail. He made some very interesting observations on the Galapagos Islands, west of Ecuador, in particular."
"Tell me about them."
"The Galapagos Islands are a compact group of volcanic islands. There were therefore no great differences in the plant and animal life there. But Darwin was interested in the tiny differences. On all the islands, he came across giant tortoises that were slightly different from one island to another. Had G.o.d really created a separate race of tortoises for each and every island?"
"It"s doubtful."
"Darwin"s observations of bird life on the Galapagos were even more striking. The Galapagos finches were clearly varied from island to island, especially as regards the shape of the beak. Darwin demonstrated that these variations were closely linked to the way the finches found their food on the different islands. The ground finches with steeply profiled beaks lived on pine cone seeds, the little warbler finches lived on insects, and the tree finches lived on termites extracted from bark and branches ... Each and every one of the species had a beak that was perfectly adapted to its own food intake. Could all these finches be descended from one and the same species? And had the finches adapted to their surroundings on the different islands over the 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 G.o.d 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 pa.s.sed 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 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 succ.u.mb 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 happens?"
"Yes, but it"s not only a question of food. It can be just as vital to avoid being eaten by other animals. For example, it can be a matter of survival to have a protective camouflage, the ability to run swiftly, to recognize hostile animals, or, if the worst comes to the worst, to have a repellent taste. A poison that can kill predators is quite useful too. That"s why so many cacti are poisonous, Sophie. Practically nothing else can grow in the desert, so this plant is especially vulnerable to plant-eating animals."
"Most cacti are p.r.i.c.kly as well."
"The ability to reproduce is also of fundamental importance, obviously. Darwin studied the ingenuity of plant pollination in great detail. Flowers glow in glorious hues and exude delirious scents to attract the insects which are instrumental in pollination. To perpetuate their kind, birds trill their melodious tones. A placid or melancholy bull with no interest in cows will have no interest for genealogy either, since with characteristics like these, its line will die out at once. The bull"s sole purpose in life is to grow to s.e.xual maturity and reproduce in order to propagate the race. It is rather like a relay race. Those that for one reason or another are unable to pa.s.s on their genes are continually discarded, and in that way the race is continually refined. Resistance to disease is one of the most important characteristics progressively acc.u.mulated and preserved in the variants that survive."
"So everything gets better and better?"
"The result of this continual selection is that the ones best adapted to a particular environment-or a particular ecological niche-will in the long term perpetuate the race in that environment. But what is an advantage in one environment is not necessarily an advantage in another. For some of the Galapagos finches, the ability to fly was vital. But being good at flying is not so necessary if food is dug from the ground and there are no predators. The reason why so many different animal species have arisen over the ages is precisely because of these many niches in the natural environment."
"But even so, there is only one human race."
"That"s because man has a unique ability to adapt to different conditions of life. One of the things that amazed Darwin most was the way the Indians in Tierra del Fuego managed to live under such terrible climatic conditions. But that doesn"t mean that all human beings are alike. Those who live near the equator have darker skins than people in the more northerly climes because their dark skin protects them from the sun. White people who expose themselves to the sun for long periods are more p.r.o.ne to skin cancer."