A History of Evolution/Chapter 1
CHAPTER I.
EVOLUTION AMONG THE GREEKS.
The earliest known books on natural history, and particularly on zoology, the science of animals, were those written by the ancient Greeks. We are certain that still more ancient volumes once existed, for the Greek writers commonly referred to "the ancients," very much as authors of today refer to the Greeks. But who these ancients were, where they lived, and what they wrote, we have no means of knowing; for all practical purposes the study of animal life may be considered to have originated in Greece during the seventh century before the Christian era.
Never, perhaps, has a talented people been so advantageously situated with relation to a stimulating environment as were the Greeks. All about them was a sea teeming with low and primitive forms of life, stimulating them to the observation of nature. Their earliest philosophies were philosophies of nature, of the beginnings and causes of the universe and its inhabitants. Of course, as has been pointed out by various students of philosophy, the Greeks did not follow truly scientific methods of thought; they aimed directly at a theory without stopping to search for a mass of facts to suggest and support it. Neither, for that matter, can they justly be called scientists or naturalists; rather, they were poets and philosophers, and their evident failures to understand the problems which they attacked are quite to be expected. As has been said, they sought the theory before they searched for the fact, and having attained it they interpreted all facts in the light of the theory. And if that was wrong—as it very often was—the whole thing was wrong, because only the theory was studied and no one knew anything about the mistake.
But with all their superstitions and erroneous ideas, the Greeks possessed an overpowering curiosity regarding the multitudinous natural objects which they saw about them. Thales, an Ionian astronomer who lived from 624–548 B. C. was the first, so far as we know, to substitute a natural explanation of "creation" for the prehistoric myths. He believed that water was the fundamental substance from which all things come, and because of which they exist. Thus the idea of the marine origin of life, held today by many prominent biologists, is found to be extremely ancient. Of course, had Thales lived in a land-locked country instead of one surrounded by a warm, highly populated sea, his ideas might well have been different. Thus we must, at the very outset, attribute to environment as well as to intellect the reliability of an important Greek idea.
Anaximander (611–547), another astronomer, was the first important Greek evolutionist. He believed that the earth first existed in a fluid state. From its slow drying up were produced all living creatures, the first being man. These water-dwelling humans appeared as fishes in the sea, and came out upon the land only when they had so far developed that they were able to live in the air. The capsule-like case which enclosed their bodies then burst, freeing them and allowing them to reproduce their kind upon the continents. In his ideas of the origin of life Anaximander was the pioneer of "Abiogenesis," teaching that eels, frogs, and other aquatic creatures were directly produced from lifeless matter.
Anaximander's pupil, Anaximenes, departed radically from the teachings of Thales. He thought that air, not water, was the cause of all things, yet he held that in the beginning all creatures were formed from a primordial slime of earth and water. Another pupil of Anaximander, Xenophanes (576–480), made himself famous by discovering the true nature of fossils. Before his time, and indeed, for thousands of years afterward, fossils were held to be accidents, or natural growths, or creations of a devil, or of a god who delighted in puzzling his earthly children. Xenophanes. rightly interpreted them to be the remains of animals, and from this concluded that seas formerly covered what is now dry land.
Empedocles, (495–435) taught what is probably the first clearly formulated theory of evolution. He supposed that many parts of animals, such as heads, legs, necks, eyes, ears, and so on, were formed separately, and were kept apart by the mysterious forces of hate. But love of part for part finally overcame the baser passion, and the various sections came together to form bodies. The combinations, unfortunately, were entirely accidental, and did not always result in satisfactory creatures. One body, for example, might possess several heads and no legs; another might have an abundance of arms and legs, but be without a head. These monstrosities were unable to keep themselves alive, and so perished, leaving the world to the bodies that had come together in proper combinations. Thus Empedocles, more than two thousand years before the first zoologist framed and taught a theory of organic evolution that seemed to offer anything worth while, conceived one of the most important of evolutionary principles—that of natural selection.
But by far the most striking figure among the early Greek philosophers who gave their attention to natural history was Aristotle, (384–322). He lived more than three hundred years before the Christian era, and was a pupil of Plato and a teacher of Alexander the Great. He wrote upon a wide variety of subjects—politics, rhetoric, metaphysics, psychology, philosophy, and natural history—and published several hundred works, most of which have been lost. It is true that Aristotle's books are full of errors, and if the philosopher were to be judged by the standards of twentieth century science he would not appear very important. But it must be remembered that he was a pioneer who, by the force of his own ability created the serious study of natural history. The workers who had preceded him had discovered relatively little; their works were mostly speculations and vague hypotheses. As Aristotle himself says, "I found no basis prepared; no models to copy … Mine is the first step, and therefore a small one, though worked out with much thought and hard labor. It must be looked at as a first step and judged with indulgence. You, my readers, or hearers of my lectures, if you think I have done as much as can be fairly required for an initiatory start, as compared with more advanced departments of theory, will acknowledge what I have achieved and pardon what I have left for others to accomplish."
In his two books, "Physics" and "Natural History of Animals" are set forth Aristotle's views on nature, and his remarkably accurate observations of both plants and animals. He distinguished about five hundred species of mammals, birds, and fishes, besides showing an extensive knowledge of corals and their allies, sponges, squids, and other marine animals. He understood the adaptation of animals and their parts to the needs placed upon them, and was familiar with the commoner principles of heredity. He considered life to be a function of the animal or plant exhibiting it, and not a separate entity, given out by some divine power, or mysterious force. Aristotle devised a hereditary chain, extending from the simplest animals of which he had knowledge to the highest, man. This chain was a very direct affair, not at all resembling the modern "evolutionary tree" in its various ramifications and irregularities. And yet, despite its deficiencies, this chain was the best conception of animal development and descent to be produced in more than twenty centuries.
Unfortunately, Aristotle saw nothing of value in the crude survival suggestion of Empedocles. He believed that there was a purpose, a continued striving after beauty, in all the variations of plants and animals, and allowed nothing whatever to what we, for lack of better knowledge, call "chance variation." He did, however, restate Empedocles' position in modern, scientific language in order that he might refute it the more ably. He argues strongly for his conception of purpose in evolution, saying, "It is argued that where all things happened as if they were made for some purpose, being aptly united by chance, these were preserved, but such as were not aptly made, these were lost and still perish." He then makes reference to the way which Empedocles used this conception to explain the non-existence of the mythical monsters of olden time, states again that nothing is produced by chance, and closes with the statement, "There is, therefore, a purpose in things which are produced by, and exist from, Nature."
Aristotle was far and away ahead of any other evolutionist of ancient times; indeed, had he turned his genius to the clarification and support of the survival hypothesis, instead of combating it, he might have been properly considered as the "Greek prophet of Darwinism." His teachings were opposed by the philosopher Epicurus, who lived from 341 to 270 and was one of the most prominent figures of ancient rationalism. Epicurus did not believe in anything supernatural; he maintained that everything could be explained on a purely natural and mechanical basis. He excluded teleology, the doctrine of a conscious plan or purpose in evolution and nature from any place in true philosophy, thus taking an important stand in a struggle not yet settled. Unfortunately, Epicurus did not take the trouble to explain what his postulated natural causes were, or how they behaved. The agnostic may well say, with Elliot, that the organic world seems to be teleologically organized merely because it cannot be organized otherwise, but he must stand ready to show grounds for his statement.
After Epicurus we must pass from Greece to Rome. T. Lucretius Carus (99–55), more commonly known as Lucretius, revived the teachings of ancient Greek philosophers and united them with those of Epicurus, whose doctrines he made famous in the long poem, "De Rerum Natura." Lucretius maintained a purely mechanical, rationalistic view of nature, but ignored the valuable work of Aristotle. He revived Empedocles' hypothesis of survival, but confined its application to the mythical monsters of past ages—centaurs, chimeras, and so on. He believed in the spontaneous generation of life, speaking of mounds arising, "from which people sprang forth, for they had been nourished within." "In an analogous manner," says he, "these young earth-children were nourished by springs of milk."
Thus we see that Lucretius, although an excellent poet, was neither a good evolutionist nor a first-rate philosopher. In his abandonment of Aristotle he discarded the only phase of Greek thought which had come near to true conceptions of evolution, and in expounding the doctrine of spontaneous generation, he fostered an idea that was to prove of almost infinite harm to the evolution idea.
There was no one to carry on the work. Greece was no longer a great nation; her "philosophers" were mostly second-rate tutors. Rome produced no naturalists of note, Pliny, the greatest, being of small capacity for reliable observation. The Greeks had done much; they had asked questions and insofar as they were able, had given answers. They left the world face to face with the problem of natural causation, and their ideas endured as a basis for the work of future scientists and philosophers.
THE GREEK PERIODS[1]
| GENERAL CONCEPTION OF NATURE: | DIVISIONS OF THE SCHOOLS |
| Mythological | The prehistoric traditions, |
| I. The Three Earliest Schools. | |
| FIRST PERIOD: | The Ionians: Thales (624–548), Anaximander (611–547), Anaximenes (588–524), Diogenes (440– ). |
| Naturalistic | The Pythagoreans (580–430). The Eleatics. Xenophanes (576–489). Parmenides (544– ). |
| II. The Physicists. | |
| Materialistic (Early) |
Heraclitus (535–475), Empedocles (495–435), Democritus (450– ), Anaxagoras (500–428). |
| SECOND PERIOD: | Socrates (470–399), Plato (427–347). |
| Teleological | Aristotle (384–322). |
| The Post-Aristotelians, (so-ealled Peripatetics), inecluding Theophrastus, Preaxagoras, Herophilus, and others. | |
| A. I. The Stoics. | |
| THIRD PERIOD: | II. The Epicureans. |
| Epicurus (341–270). | |
| Materialistic | III. The Sceptics. |
| (Late) | B. I. Eclecticism. |
| Galen (131–201 A. D.). |