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Biology, I (History of)


Biology is the experimental science that studies living things and their vital activities. It takes its origin from the natural human desire to know what living things are and what they do, but also, and more generally, from a practical interest in acquiring food, clothing, shelter, and protection, and in curing sickness. People sometimes tried to obtain these things, and especially cures, by supplicating the gods and having recourse to magic. People often also used a pragmatic approach, however, to determine things such as what foods were edible and where game was most likely to be found. In this way empirical knowledge about diet, medicinal herbs, and the raising of crops and animals gradually accumulated. Around the 7th century b.c. a new mentality manifested itself among the Greeks. The Greek quest for knowledge was motivated by wonder, a desire to know the causes of things, a desire satisfied only though observation and logical reasoning. The spirit and achievement of such research were embodied in the works of the father of medicine, hippocra tes (fl. 400 b.c.). Most of the 60 or 70 separate treatises attributed to him were written over a period of several centuries. In these treatises are found not only remedies for different illnesses that are the fruits of empirical observation, but also an attempt to understand what the causes of illnesses are, and why the remedies work. The attempts at causal explanation were often far from the mark, but still represent a step beyond pragmatic generalizations.

Greek Period. The origin of biology as a science seeking knowledge of living things for its own sake, rather than for the sake of contributing to human well-being, is found above all in the works of aristotle (c. 384322 b.c.). Aristotle founded biology as a school and was the foremost biologist of antiquity.

Aristotle's studies of living things can be divided into three kinds. He regarded living things as composed of matter and form, and he regarded the soul being the natural form distinguishing living natural things from other natural things. His treatise On the Soul treats the soul in itself. The second kind of treatise studies those activities of living things that are explained in terms of both soul and body, but chiefly in terms of the soul (e.g., On Memory, On Sense and Sensation ). The final group of treatises examine those aspects of living things that are understood chiefly in terms of the body (e.g., Parts of Animals, Generation of Animals ). In these latter treatises Aristotle first seeks to establish what the facts are, and then to seek causal explanations for them. His insistence on observation, his search for causes behind observed facts, his emphasis on seeking the final causes of organisms' parts and activities, along with his use of biological methods such as dissection and even (some limited) experiment, and his development of biological concepts, such as that of classification, have merited him the title of Father of Biology.

In addition to his contribution to the development of biology as a science, Aristotle made numerous observational contributions to biology. In many of his writings on natural history he faithfully extended the Hippocratic tradition of making generalizations from collected observations. Acquainted with the characteristic features of mammals, he was able to recognize whales, dolphins, and porpoises as properly belonging to this group and not to the fishes. He knew that some fish bring forth their young alive, and that one in particular approaches the mammals even more closely in that its young develop within the uterus of the female and are attached to a type of placenta. The existence of the placental dogfish and other facts unearthed by Aristotle were not substantiated until the 19th century. In an incubating hen's egg, Aristotle followed the day-by-day development of parts from a relatively homogeneous mass. None of Aristotle's botanical treatises have survived, but a few works by Theophrastus, his pupil, successor, and the father of botany, have come down to us. In his description of the parts of plants (plant anatomy), Theophrastus sought to devise a technical terminology. He valued developmental study (embryology) and distinguished various modes of plant reproduction.

After Aristotle and Theophrastus interest in biology as a scientific understanding of living nature for its own sake waned, and practical concerns regained center stage. From around 300 to 150 b.c. some discoveries were made in anatomy and physiology, two of the more noteworthy contributors being Herophilus and Erasistratus.

Roman Period. About the middle of the 2d century b.c., Greece succumbed to the Roman legions. The Romans made contributions in politicsbut their interest in science was primarily in its application. Thus, in biology, both medicine and agriculture were encouraged because of their importance to the welfare of the army and the empire. Of note are Pliny, Dioscorides, and Galen.

Pliny the Elder (a.d. 2379) put together a natural history of 37 volumes. This work influenced the development of biology and natural history throughout the Middle Ages in chiefly a negative way. In this encyclopedia of nature, Pliny mixed fact and fancy, and did not use scientific standards as a guide as can be seen from the anecdotes he recounts, such as the bear licking its cubs into shape. Soon after Christian authors, taking inspiration from Pliny, composed stories about animals to convey moral and religious messages. The medieval bestiaries were the continuation of this tradition of combining wonderful stories of birds and beasts with miracle and allegory.

Dioscorides (c. a.d. 4090) was a Greek who worked under Nero as an army surgeon. He originated the pharmacopoeia, tersely describing plants of value to medicine and frequently including their habits and habitats. Annotated copies of this materia medica formed the chief source of pharmocological knowledge for the next 1,500 years.

The 2d century a.d. saw the last great biologist of antiquity, Galen of Pergamum, who standardized anatomy and physiology for the next 15 centuries. Court physician to Marcus Aurelius, he composed voluminous works containing the ideas of his predecessors as well as his own contributions. He described from dissections, and performed experiments on living animals. By severing the spinal cord of living animals at different levels he gained knowledge of nerve functions. Galen also distinguished between motor and sensory nerves. His knowledge of physiology and anatomy allowed him to effect cures when other physicians failed. Posing an obstacle to Galen's investigation was his inability to procure human cadavers for dissection. Consequently he relied chiefly on his dissections of the Barbary ape for an understanding of the human body, which resulted in his making a number of errors. Galen's brilliance had as an unfortunate side effect that he was taken as an absolute authority for many centuries.

Middle Ages. From many and varied causes that had been building up for centuries, the Western Empire crumbled in the 6th century. With the barbarians invading from the north, scientific progress came to a standstill. The few important links with the learning of the past were the hand-copied manuscripts carefully guarded in the monasteries of Britain and Italy. Although this period of the Middle Ages was not a time of scientific progress and experiment, men were trained to think. The habit of definite, exact thought was implanted in the European mind by theologians and philosophers of the late Middle Ages. With the spread of Islam after the death of Muhammad, the almost forgotten culture of the Greeks and the Near East was reintroduced into Western Europe. From the 9th to the 11th centuries this transmission vivified medieval thought with Arabic translations of Plato, Aristotle, Theophrastus, and others. During this period Avicenna (9801037) wrote his famous "Canon" of medical science, which remained for centuries the principal authority in medical schools in both Europe and Asia.

By the 13th century the translations of Aristotle's zoological works provided an alternative to the bestiaries with their fabulous accounts, opening people's eyes to what true biological inquiry consisted in. Albert the Great's (1206?1280) commentaries on Aristotle's zoological works include his personal observations of animals.

Renaissance. During the Renaissance, the sciences flourished. Biology did not, however, develop quite so rapidly as physics did. The reasons for this are that the object studied by the biologist is much more complex, and also that mathematics, a powerful tool for the physicist, is of relatively little use in biology. Moreover, it was oftentimes knowledge of physics that was behind the development of biological instruments such as the microscope. Indirectly, however, physics also had a negative impact on the development of biology. Thinkers such as René Descartes promoted the notion that organisms were merely machines, the study of which was to be reduced to physics. This retarded the development of an autonomous method in biology for quite some time, and limited the study of psychology to human beings.

The restlessness, probing curiosity, and many-sided learning of the Renaissance are epitomized in Leonardo da Vinci (14521519). Known primarily as an artist, he was also a talented engineer, inventor, observer of nature, and anatomist. Had his notes and drawings in human anatomy been published when made, anatomy might have been advanced by a century. He made scientific studies of the action of the eye, the mechanisms of various joints, and of the flight of birds. Embryological and comparative anatomical studies alike came within the compass of his work.

Biology in the 16th century is represented in the herbals, encyclopedias of nature, and monographs of the period. The German fathers of botany produced herbals that ranged from annotated texts of Dioscorides, like that of Otto Brunfels (14891534), to the beautifully illustrated manual of Leonhard Fuchs (150166), which was intended as a guide for the collection of medicinal plants in Western Europe. The encyclopedias attempted to gather together in one work all of the available knowledge about living things. The most influential of these was the History of Animals by Konrad Gesner (151665) of Switzerland, probably the most learned zoologist of the period. Some of Gesner's less ambitious contemporaries confined their efforts to treatises or monographs on special groups of organisms.

Human anatomy in the Renaissance was studied through a slavish interpretation of Galen by the teacher, while an attending barber's assistant crudely made the actual dissections. By his own skilled and careful dissections, however, Andreas Vesalius (151464) of Belgium showed his anatomy students at Padua that Galen, great as he was, could be wrong. In 1543 he published his wonderfully illustrated book, On the Structure of the Human Body, which marked the end of the servile adherence to the authority of the past.

Until the functioning of the heart and blood was understood it was impossible to grasp the natural ordering of the bodies of the higher animals. The publication in 1628 of William Harvey's (15781657) treatise On the Motion of the Heart and Blood in Animals was a large step forward in understanding anatomy. Numerous observations, carefully planned and executed experiments, and quantitative calculations led Harvey inductively to the conclusion that the heart is a muscular pump that propels the blood in a closed circuit throughout the vertebrate body. John Ray (16271705) is noted for his work in taxonomy. Ray sought to establish a system of classification of both plants and animals in which species sharing characteristics are shown to be related by their classification and nomenclature. Ray made careful studies of comparative anatomy, and used them as basis for his animal taxonomy. His work represents a huge step forward from the previous alphabetical lists of species, and it provided direction to later taxonomists such as Carolus Linnaeus.

In the 17th century the compound microscope was added to the apparatus of the biologist. As used by such men as Nehemiah Grew (16411712) in England and Marcello Malpighi (162894) in Italy to study the fine structure of living things, it led to the development of a new branch of biology called histology. The world of microbes was first seen by Antoni van Leeuwenhoek (16321723) through his homemade lenses, and microbiology was born. The microscope allowed biologists to observe entities that previously were only hypothetical, e.g., disease agents such as bacteria.

18th Century. In the 18th century new impetus was given to biology by the comparative method applied to anatomy and embryology. The classification (taxonomy) of living things as well as a system of naming them (nomenclature) were standardized. Georges Cuvier (17691832), the founder of modern comparative anatomy and paleontology, was able with his knowledge of animal structures and by the application of the theory of the "correlation of parts" to place many fossil forms in their correct systematic positions in the animal kingdom. He surmised that each species was specially created and that the existence of dissimilar fossils in series of rock strata could be explained by catastrophism. According to this theory, wide expanses of the earth were from time to time subjected to great cataclysms (floods, quakes, etc.), which obliterated all life in those areas. Later, such territory would be populated by different animal species, which migrated into the denuded areas from distant parts. These would eventually leave some descendants in the fossil record that would contrast with the fossils in the lower strata of sedimentary rocks.

The most important figure in 18th-century biology was Carolus Linnaeus (170778) of Sweden. From his youth, he had displayed a passion for classification and an extraordinary genius for accurate and detailed observation. He visited and collected plant specimens in Lapland, Norway, France, Germany, Holland, and England. As an outcome of these travels and studies he wrote his famous Systema naturae, published in Holland in 1735, in which he attempted to describe and classify every known animal and plant. In so doing he set standards for describing animals and plants with accuracy and succinctness.

During most of his life, Linnaeus firmly adhered to the idea that all of the present-day species of plants and animals were the unchanged linear descendants of original species individually created. When Linnaeus observed how plants of different species hybridize, however, he was led to revise his initial conceptions. In his Fundamenta fructificationes (1762) he conceded that perhaps there was a common stock for all of the species of a single genus, or even perhaps of a single order. The direct work of the Creator was confined then to the genera, or to the orders, the diversification of which was accomplished as a result of crossing or hybridization.

19th Century. Advances far-reaching in their effects were made in biology in the 19th century. The enunciation of the theory of evolution colored the thought of the period in many fields extraneous to biology. The germ theory of disease affected our entire civilization, as did the discovery of the basic laws of inheritance. Slightly less notable were the formulation of the cell theory and the advances in embryology and physiology. In this period the method of testing hypotheses through controlled experiment is spoken of explicitly by the biologist Claude Bernard (181378) and begins to be more widely used.

The term "cell" in its biological sense comes down from the 17th-century work of Robert Hooke (16351703), who thus described the tiny divisions that he saw in thin slices of cork under the microscope. The formulation of the cell theory was, however, a gradual development of the early 19th century. In brief, the cell theory states that all organisms are composed of cells (or a single cell) that are essentially alike in their composition and formed in the same fundamental manner by division of a preexisting cell. The basic points of the cell theory were stated and confirmed with clear-cut observations by Matthias Schleiden (180481) and Theodor Schwann (181082), in 1838 and 1839, respectively. The study of cells, cytology, became a distinct branch of biology in the 20th century.

Although crude ideas of evolution can be found among the Greek philosophers, it was not until the 19th century that a definite theory of evolution was presented. "Theory of evolution" is an ambiguous expression. It sometimes names the notion that species of living things took their origin from priorly existing species, instead of appearing without any reproductive continuity with them, as supported by evidence from different areas of biology. At other times theory of evolution names the various causative explanations offered for how species could originate one from another over time. J. B. de Lamarck (17441829) proposed as causal mechanism the inheritance of acquired characteristics. He believed that a felt need on the part of an organism might give rise to new organs and suggested that the use of an organ or part strengthens and develops it, while a lack of its use leads to a gradual atrophy, diminution, and eventual disappearance.

Evolution, however, has become almost synonymous with the name of Charles darwin (180982). No other publication has exerted so profound an influence on biology as his book The Origin of Species by Means of Natural Selection (1859). In Origin of Species Darwin both presents evidence that species have evolved, and presents a causal explanation for evolution, namely, chance variation subjected to natural selection. Darwin had spent 20 years gathering facts to substantiate his views. Although the same ideas were arrived at independently by Alfred Wallace at the same time, Wallace had not the same wealth of observational data to support them as had Darwin. Each had published a short presentation of his views in the same issue of the Proceedings of the Linnean Society the previous year. The first edition of The Origin of Species was sold out on the first day of its publication, and it brought forth a storm of controversy in the fields of religion and sociology, which continues to this day. (see evolution.)

In the 16th century, the Italian physician Girolamo Fracastoro (14831553) had contended that infection of all kinds, including fermentation, was the work of minute "seeds" or germs. This was proven by Louis Pasteur (182295) on experimental grounds. Though Pasteur was a chemist, his great discoveries were in microbiology and preventive medicine. He showed that such diseases as rabies and anthrax could be prevented by inoculation with the attenuated or even dead germs causing the disease.

Genetics is that branch of biology concerned with the phenomena of inheritance and the origin of heritable variations. Although genetics did not emerge as a full-fledged science until well into the 20th century, the basic laws of inheritance upon which it is founded were discovered by an Augustinian monk, Gregor mendel (182284); his work marks the beginning of precise knowledge of genetics. Working principally with garden peas, he combined the experimental breeding of pedigreed strains of plants and the statistical treatment of the data secured in regard to the inheritance of sharply contrasting characteristics, such as short and tall plants, or white and red flowers. His work, published (1866) in an obscure journal, remained almost wholly unnoticed until 1900.

August Weismann (18341914), who opposed the theory of the inheritance of acquired characteristics, published (1892) a volume entitled The Germ Plasm. He identified the chromosomes found in every cell nucleus as the bearers of hereditary traits and emphasized a sharp distinction between germ cells and somatic cells.

20th Century. One of the three men who had independently discovered Mendel's work in 1900 was a Dutch botanist, Hugo de Vries (18481935). His work in plant breeding had convinced him of the significance of the distinction between heritable and nonheritable variations. Among his plants he found variations in some individuals that marked them distinctly from the parent generation, and he discovered further that these bred true. In his book The Mutation Theory, he proposed that evolution proceeded by means of rather large mutations or saltations. This contrasted with Darwin's concept that natural selection had acted upon small, continuous, heritable variations. T. H. Morgan (18661945) showed that mutations occur constantly and range from minute, barely perceptible changes in structure and function to the large, discontinuous variations of the type considered by de Vries, but most were in the category of minute changes.

Morgan actually followed up the work of another American experimental zoologist, E. B. Wilson (18561939), who had opened the way with his studies in cellular biologyparticularly those dealing with the chromosomes and their relation to heredity. H. J. Muller (18901967), who received the Nobel prize for his investigations in genetics, showed that the frequency of gene mutations is affected by temperature, age, and the stocks used. He discovered that ionizing radiations would speed up the mutations that normally occur at a relatively slow rate.

In the beginning of the 20th century it was still unknown what the hereditary material was. Proteins were the most likely candidates for this role. Nevertheless, evidence slowly began accumulating that chemically simpler DNA was in fact the hereditary material. In the 1920s Frederick Griffiths discovered that he could transform nonvirulent bacteria into virulent bacteria by mixing live nonvirulent bacteria with dead virulent bacteria. Apparently the live nonvirulent bacteria had taken up some chemical transforming principle from the dead virulent bacteria. In 1944 Oswald T. Avery, Colin MacLeod, and MacLyn McCarty isolated DNA from an extract containing the transforming principle, and showed that it alone of the substances in the extract caused bacteria to transform. Another experiment performed in 1952 by Alfred D. Hershey and Martha Chase gave further support to the notion that DNA is the carrier of hereditary information. The structure of DNA was elucidated in 1953 by James D. Watson and Francis Crick. DNA is a double helix composed of two strands held together by hydrogen bonds between complementarily paired bases. A great deal of subsequent research was devoted to understanding how DNA replicates and how the information contained in it is ultimately translated into the proteins that serve constitutive and other functions in the body. Some recent advances include the sequencing of the genomes of a variety of organisms including homo sapiens, the cloning of higher organisms, and genetic engineering, a process whereby genes are inserted into organisms allowing them to produce substances they normally would not produce.

The other dominant area of biology at the beginning of the 21st century, one that shares close ties to genetics, is cell biology. The interest in these areas lies in the possibility of discovering knowledge that can be used for developing cures for disease. Both genetics and cell biology seek an understanding of life processes in molecular terms. The crude earlier understanding of a cell as protoplasm along with a nucleus contained by a membrane has been replaced by a continually expanding knowledge of the specific constituents and chemical reactions going on in the cell.

Alongside modern genetics and cellular biology that try to understand life processes in physico-chemical terms are three other disciplines that adopt a more global approach: evolutionary biology, ecology, and ethology. Evolutionary biology drew profit from the work of geologists who, rejecting the catastrophism of Cuvier, developed new principles for relative age dating of rocks and devised reliable absolute dating techniques. Much work is currently being done in an attempt to trace the evolutionary history of the various species. Refinements have also been made in the area of evolutionary theory. The most prevalent theories are referred to as "neo-Darwinian" since they integrate the key notions of Darwin's theory with the discoveries made in genetics. There is disagreement among neo-Darwinians, but it is slight compared to that which exists between the neo-Darwinians and those in the Intelligent Design movement. Proponents of the latter group maintain that random variation sorted out by blind natural selection cannot adequately explain the order found in the organs and activities of living things.

Ecology deals with the relationships between living things and their natural environment in both its physical and biotic aspects. This sort of study is already found in the natural history of Aristotle. The science, however, took on new life at the end of the 19th century with the work of F. A. Forel (18411912) and E. A. Birge (18791941), among others. Emphasis was placed on studying populations, communities, and habitats. Increasing use was made of quantitative and statistical methods.

Ethology or the study of animal behavior has its origin in observations made early on by humankind. Modern ethology took a new beginning with the work of Konrad Lorenz (190389) and Niko Tinbergen (190788). These scientists sought to understand not only why animals perform certain actions, but also the causal mechanism behind the behavior (e.g., what hormones must be produced for a bird to be able to learn its song). Present-day ethology also has as its goal determining the evolutionary history of animal behavior.

Bibliography: g. a. sarton, A Guide to the History of Science (Waltham, Mass. 1952); g. sarton, Introduction to the History of Science, 3 v. in 5 (Baltimore 192748) v. 1. a. n. whitehead, Science and the Modern World (New York 1925). l. thorndike, Science and Thought in the Fifteenth Century (New York 1929);l. thorndike, A History of Magic and Experimental Science, 8 v. (New York 192358). e. nordenskiÖld, The History of Biology (new ed. New York 1935). aristotle, Works, tr. w. d. ross, 12 v. (Oxford 190852) v. 4 Biological treatises: e. rÁdl, History of Biological Theories, tr. e. j. hatfield (London 1930). c. j. singer, Greek Biology and Greek Medicine (Oxford 1922); History of Biology to about the Year 1900 (3d ed. rev. New York 1959). f. j. cole, History of Comparative Anatomy (London 1944). a. r. hall and m. b. hall, A Brief History of Science (Toronto 1964). j. l. gould, Ethology: The Mechanisms and Evolution of Behavior (New York 1982).

[p. stokely]

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