HISTORY OF BIOLOGY HOW KNOWLEDGE OF LIFE EVOLVED
This short historical overview is not meant to be memorized. The dates are put for accuracy, and the names to honor people who have contributed to human progress.
1. "Natural history" in ancient Greece and Rome
Humans have always been interested in the living world. Even primitive hunter-gatherers have some "biological" knowledge (if you have seen the movie "The Gods Must Be Crazy", remember how bushman Xi was hired as an ecologist). Ancient civilizations of Egypt, Messopotamia and China had much knowledge of plants and animals and used fermentation. However, this knowledge was purely practical.
Much greater progress was achieved in ancient Greece, whether first "seeds" of science appeared. However, true science did not develop until much later. This was due to the one-sidedness of Greek minds. They had brilliant deductive thinking and develop excellent mathematics and phylosophy. This misled them even in studying the natural world to trust what was coming from their mind, rather than what they were seeing. However, natural sciences are inductive and require not only deductive reasoning, but also matching conclusions to facts.
Anaximander (6th century BC) supposed that living creatures originated in water and then fish developed into terrestrial animals and humans. Xenophanes (6th and beginning of 5th century BC) observed fossil shells, mentioned their resemblance to shellfish and concluded that the land he found them had been sea bottom before. Empedocles (5th century BC) developed a fantastic "natural selection" theory. He said that first appeared separate body parts: heads, eyes, extremities. They combined in various ways, e.g. head and torso oriented in opposite directions, human body with bovine head or vise versa. Finally, only the successful combinations survived as we know them today.
The atomists Leucippe and Democrites (5th century BC), developed a materialistic and mechanistic phylosophy. Here is the place to tell about different phylosophies. Although phylosophy lies ouside the realm of the scientific method, it matters: some phylosophies provide a good basis for natural sciences, others exactly the opposite.
How is the Universe ruled? The answer to this question divides phylosophies into materialistic and idealistic ones. According to materialists, this is done by a set of laws of nature universal rules which can be studied by the scientific method. According to idealists, the world is controlled by supernatural (i.e. inidentifiable by the scientific method) forces, often regarded as conscious. The name idealism likely comes from Plato's works (4th century BC). This early idealist regards objects as inferior copies of divine prototypes called ideas, which can be studied by mind but not by observation. Plato has much influence, even during the Middle Ages when ancient heritage was rejected. Althouth he is a great phylosopher (at least no one other phylosopher dares to say the opposite), his views hinder progress. It is difficult to make science if you have been brainwashed to believe that the entire visible world is a second-quality imitation of some perfect invisible world.
In what direction do natural phenomena evolve? The answer to this question divides phylosophies into mechanistic and teleological. According to teleology, every process has a definite purpose. Here is an example of a teleological question and answer: "What is the purpose of evolution? To bring man into existence." According to mechanism, an event is followed by another event because the former has caused the latter or simply allowed it to happen (mechanism does not exclude chance). It is clear that materialism is related to mechanism and idealism to teleology.
The appropriate phylosophy for science is mechanistic materialism. Idealism and teleology have nothing to do with science they belong to other areas of thought. This does not mean that the scientist must be an atheist but simply that, when solving scientific problems, he must not "find" the answers in God's will. God is not fit as a hypothesis not only because He is, by definition, outside the range of the scientific method, but also because with Him you can explain everything. This means, in fact, that you can explain nothing. For example, the "theory" that God has created life is compatible not only with all known facts, but also with all facts that can ever be found. Every scientific theory must be rejectable; if it can match all possible facts, it contains no information and is of no value.
Leucippe and Democrites had "the correct" phylosophy. They thought life had evolved from "primitive mud" and living things, including their souls, consisted of atoms similarly to the non-living matter. The term we translate as "soul" meant a hypothetical entity bringing life to an object. In ancient and medieval times most people thought it supernatural; the atomists were an exception. As we see below, the Industrial revolution made the soul unnecessary.
Aristotle (4th century BC) described over 500 species, mostly animals, and dissected many of them. He classified animals and developed a teleological evolutionary theory. Unfortunately, Aristotle introduced into natural history unappropriate idealistic phylosophy. His most serious error was the hypothesis of spontaneous generation of organisms from non-living matter or other organisms.
2. Biology from the Middle Ages to modern times
After the decline of ancient mediterranean civilizations their territories were populated by, to say the least, underdeveloped people. The only civilizing force was the church, but is was hostile to science and extremely intolerant. Intellectual life in Western Europe hit a minimum between 600 and 1000 AD, the so-called Dark Ages. The ancient heritage was so thoroughly forgotten that later Europeans had to learn it in transcriptions of Arab authors.
Beginning with 11th century, rationality slowly revived. In 12th century the available scientific literature was translated from Arabic to Latin, which later became the international language of science. The "new" knowledge was first met with suspicion because of its non-Christian origin. In 13th century, Albertus Magnus convinced people that even non-Christians could write truth and it this case it was no sin for a Christian to accept their theories. Among the rediscovered authors, most valued was Aristotle. Unfortunately he was turned into a dogma, i.e. his theories were thought to be true without matching facts, just because they were created by him.
In later centuries, technology developed and changed human minds. Ancient and medieval people had no engines and knew only two groups of motile objects organisms and heavenly bodies. Therefore, they animated heavenly bodies, considered spontaneous movement as a characteristic of life and did not apply to living creatures the laws of physical world. The technical progress brought a change. Rene Descartes (1596 1650) created the theory of reflexes and regarded human and animal bodies as mechanisms. He described animals as automatic machines without consciousness and emotions, driven entirely by physical laws. Descartes said that humans had soul, located in the pineal gland. However, his followers unified his view, declaring even humans soulless machines. These depressing views, when applied to vertebrates, are too simplified and not quite true. But the idea of the organism-machine was a tremendous progress. For the first time the living matter was proclaimed to be entirely subjugated to physical laws and open to study.
Again in the 17th century, spontaneous generation began to be questioned first for complex organisms, then for all. Today, it is hard to believe that this theory in earlier times was supported by great scientists. An example is van Helmont (1579 1644) who introduced the term gas and found that a part of the water taken by a plant is added to its mass. Besides these and other discoveries, van Helmont left behind a recipe how to obtain mice: If a mixture of wheat, cheese and rugs is left in a quiet and dark place for several weeks, some wheat grains turn into mice. A little later, the naturalist Ross wrote, "If you doubt that beatles and wasps are generated in cow dung, then you doubt logic, common sense and experience."
The phylosophy prevailing in biology of that time was vitalism. This is an idealistic phylosophy which regards life as a result of the action of an unclear "vital force" (vis vitalis). Vitalists think that vital force can turn any piece of matter into a living creature, so the continuity of organisms is not strict.
William Harvey (1578 1657), who gave the first complete description of circulation, in his late years studied embryogenesis. He questioned spontaneous generation in a purely theoretic way. In 1651, he presented the first of aphorisms about continuity of life: Ex ovo omnia "Everything (descends) from egg". The concept of spontaneous generation of vertebrates seems to have been abandoned without experimental disproval when the complexity of their organisms was realized. The situation with invertebrates and microbes was different.
In 1668, Francesco Redi conducted an experiment to disprove spontaneous generation of larvae (maggots) in rotting meat. He covered a piece of meat with a fine mesh to prevent access of adult flies and left another piece open as a control. Maggots appeared only in the piece that was accessible to flies. Although this experiment seems too simple, compared to other achievements of 17th century science, this experiment was well planned with regard to the theory being examined. However, it failed to convince everybody.
Between 1766 and 1784, Lazarro Spallanzani performed experiments to prove that not only complex multicellular organisms but also microorganisms are not generated spontaneously. He sterilized the culture medium. However, some opponents rejected his results, saying that by heating the medium and tightly closing the bottle he destroyed the vital force.
In 1859, Louis Pasteur, better known for his work on fermentation and infectious diseases, performed and widely announced experiments meant to solve the question once and forever. He sterilized culture medium in flasks with very long, narrow and S-curved necks. The medium remained sterile for months, although it was open to air. However, when a flask was shaken so that the solution washed the neck, microorganisms that had been deposited in the neck began to grow. Pasteur stated, Omnium vivum ex vivo "Each life (descends) from life".
Vitalism could be explained as a reaction of human mind towards the unknown, an attempt to fill the large gaps in early biological knowledge. After Pasteur, vitalism found its last refuge in evolutionary and developmental biology. The processes underlying evolution and development are too complex and therefore remained unelucidated for a long time. Until almost the middle of the 20th century some scientists thought that vital force, called by different names, drives the evolution of species and forms an organism from the zygote. In fact, as Julian Huxley wrote in 1944, vitalistictic theories are no explanations at all, but mere confessions of ignorance; to say that life evolves because of vital force is the same as to say that locomotive moves because of locomotive force. These last remains of vitalism were destroyed by the discoveries of molecular genetics.
This translation is a concize verision, meant only to help you for the examination. If you speak some Bulgarian and want to see the full text (and some pictures), see the Bulgarian version at http://www.mayamarkov.com/biology/B2Istoria/B2Istoria.htm.
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Published in 2006
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