The word biology was first used about 1800. Before then the various biological sciences—such as zoology and anatomy—had been grouped together with geology and called "natural history."

The history of biology is the history of many fields, including medicine, botany, and zoology. The following is a brief account of some of the developments that apply to biology as a whole. For more details, consult the articles listed in the cross-references under the headings Specialties and Related Fields and Some Noted Biologists.

Early Biology

The first knowledge of biology grew out of primitive hunters' observations of animals and out of food-gathering and cultivation. Progress was slow, however, because nature was often considered a goddess and disease an evil spirit—and few persons dared to tamper with either. This attitude still exists among certain primitive peoples.

The earliest studies of biology were probably made by ancient physicians and embalmers. People of ancient India, China, and the Middle East had a vast knowledge of various medicinal plants. The Babylonians and Egyptians had some knowledge of human anatomy. The first man known to approach disease as a natural, rather than a supernatural, process was Hippocrates of Cos (460?-377? B.C.), a Greek who became known as the Father of Medicine.

The greatest student of biology in the ancient world was the Greek philosopher Aristotle (384-322 B.C.). His writings include encyclopedialike works on birth, death, the nature of life, and all phases of animal life. He influenced scholars for nearly 2,000 years. Pliny the Elder (23-79 A.D.), a Roman, compiled an interesting but inaccurate work on nature called Natural History. This text was widely studied for 1,500 years. Galen (130?-201? A.D.), a Greek living in Rome, studied anatomy by dissecting animals. His works were used in medical schools throughout the Middle Ages.

Although many of the ideas of the ancient writers were at least partly correct, many were also misleading or wrong. One of their mistaken ideas that lasted well into modern times was that a living body is made up of four juices, or humors—blood, phlegm, black bile, and yellow bile. Another was the theory of spontaneous generation, according to which certain living things, such as maggots, came not from other living things but from nonliving matter.

The Middle Ages

The Middle Ages saw hardly any contributions to biology in Europe. But the works of the ancient Greeks and Romans were studied by the Arabs.Scholars during the Middle Ages did not investigate nature firsthand, but confined their study to ancient books. Not only were the original writers often wrong, but bad translations caused even more errors. Virtually the only careful studies of the physical characteristics of plants and animals were those made for artistic purposes by craftsmen and artists. Some new knowledge of plants resulted from the work of the herbalists, who collected and studied herbs for use in medicine.

Later Advances

During the 14th to 17th centuries, there was a surge in the study of biology. Traditional ideas formulated by ancient Greeks and Romans were challenged. Observation and scientific study was emphasized. Scholars again turned to actual observation of plants and animals as a means of gaining information. The first really accurate textbooks on botany and zoology were written in the early 14th century. Leonardo da Vinci, the great Italian artist, dissected dead human bodies and made drawings of the human anatomy. In the same period Andreas Vesalius (1514-64), a Belgian, gave the first accurate and complete description of the human body. He was one of the first scientists since ancient times to dissect a human body.

The importance of experiment in the study of biology was shown by the Englishman William Harvey (1578-1657). He proved his theory that blood circulates in the veins and arteries by cutting into animals to show how it happens. Another important step forward was the development of the microscope in the early 17th century. Marcello Malphigi, the Italian anatomist, used the microscope to study blood circulation. Robert Hooke observed the structure of many organisms through the microscope and reported his observations in Micrographia, published in 1665. Five years later, Anton van Leeuwenhoek chanced upon organisms that could only be seen through the microscope.

By the 18th century, biologists had come to the conclusion that life could be explained in terms of biological processes that took place within the living organism. They rejected the idea of supernatural or divine intervention in biological processes. Their views formed part of materialistic physiology. In the 18th century, Antoine Lavoisier demonstrated that respiration involved the use of oxygen and the release of carbon dioxide and heat. Almost a century later, Claude Bernard pointed out that animals and plants had internal systems to ensure that conditions needed to maintain life were available. One such mechanism was regulation of body temperature in mammals.

The classification of organisms into groups began as early as Aristotle. But a really logical system was not devised until the 18th century. Carolus Linnaeus (1707-78) of Sweden refined earlier systems and developed the method of classification that (with certain changes) is still used today. His system provided a logical approach to the study of living things, and gave biologists a uniform method of description. Orderly classification also made it possible to see more clearly the relationships between various kinds of life. Linnaeus had used the similarities in structures of plants and animals to group them. This led to another field of biology—comparative anatomy. Here, different plants and animals were compared for similarities and differences. In the 18th century, Baron Cuvier proposed a system of classification where organisms were classified based on their body type.

Biologists broadened their knowledge of nature through voyages of exploration. The first important scientific expeditions were those commanded by Captain James Cook in the 1760's and 1770's. Later expeditions were made by the British ships Beagle (1831-36), on which Charles Darwin was naturalist, and Challenger (1872-76).

Important developments were made in many fields during the 19th century as biologists began to apply scientific methods to their work. Discoveries were made not only about specific organisms, but also about the nature of life in general. Early in the century it was discovered that all living things are made up of cells. In Origin of Species (1859) Charles Darwin (1809-82) gave evidence to show that complex forms of life generally evolve from simpler forms by means of natural selection. In 1865 Gregor Mendel (1822-84), an Austrian abbot, presented his findings on the principles of heredity—the first scientific studies of the subject.

Biology Today

During the 20th century, more emphasis was placed on experimental knowledge and less on theory. Systematically conducted experiments and use of statistical tools helped biologists understand the various biological processes. As biology became more scientific in its methods, it also became more useful in its practical applications. The discovery by Louis Pasteur (1882-95) of how infection is produced by bacteria, and the development of penicillin and other “wonder drugs,” contributed greatly to the control of disease.Genes have been shown to have a relationship with the kind of antibody, or disease resisting protein, produced by the body. This has helped treat deadly diseases like AIDS.

Gregor Mendel had found that physical traits are transmitted from generation to generation through units from the parent to offspring. These essential units, known as genes, are located on chromosomes within the cells, as postulated by Thomas Hunt Morgan in 1910. In 1953, James Watson and Francis Crick discovered the structure of DNA that makes up genes. This led to greater understanding of the mechanism of heredity and the process of evolution.

Research in genetics led to many new breeds of plants and farm animals, thus increasing the supply of food. Better understanding of the physical structure and habits of simple forms of life made it possible to control many types of harmful insects and other pests.

Pollution of air and water and increased use of land areas for housing and commercial development have created survival problems for various kinds of organisms. These problems have increased interest in ecology and conservation. New tools to study the complex relationships between organisms and their environment led to the development of ecology as a separate field of biology in the 1960's. There is also great interest among biologists in ethology, the study of animal behavior, especially aspects related to survival.

Space exploration has intensified interest in the possibility of life existing elsewhere in the universe. Scientists who study these possibilities, and who attempt to devise methods of detecting extraterrestrial life, are called exobiologists.

Advances in neurobiology, the study of the nervous system, has increased our understanding of how the brain and nerve cells function. Immunology, the study of the disease resistance mechanisms of the body, also benefited from the new methods and tools used in biological studies.

In basic research, the study of life processes continues, particularly in genetics and other areas of biochemistry. Since the 1950's, there has been much research involving the composition and functions of nucleic acid molecules. In the 1970's, the first successful experiments in genetic engineering were made. Genetic engineering involves the transfer of genes from one organism to another. This is very useful in agriculture and medicine, where desirable traits of certain organisms can be transferred to other organisms. Genetic engineering has raised concerns related to ethics and the potential negative effects of genetically altered organisms on the environment. This concern was particularly evident in 1996, when Ian Wilmut created the world's first cloned animal, Dolly the sheep. In the 1990's, scientists determined the complete genetic codes of a number of simple organisms, including certain types of bacteria. Gene sequencing, or mapping of all the genes in the human body, was started in the form of the Human Genome Project during the decade. Since the 1980's, advanced medical imaging techniques have been used to study many biochemical processes, including those involved in memory, language, drug addiction, mental disorders, and aging.

The American Institute of Biological Sciences (AIBS) is a professional federation of biological associations and industrial research laboratories. Its objectives are to unify and coordinate the efforts of persons engaged in biological research and teaching and to further the relationships of the biological sciences to other sciences, the arts, and industry. Publications include BioScience, a monthly. AIBS headquarters are in Washington, D.C.

Important dates in biology
c. 400 B.C. Hippocrates established the principles of modern medical practice based on the idea that diseases have only natural causes.
A.D. 100's Galen greatly extended knowledge of anatomy and physiology through his treatment of injured gladiators and dissections of apes and pigs.
1543 Andreas Vesalius's On the Fabric of the Human Body, the first scientific text on human anatomy, was published.
1628 William Harvey published his discovery of how blood circulates through the body.
1665 The first drawings of cells appeared in Robert Hooke's book Micrographia.
Mid-1670's Anton van Leeuwenhoek discovered microscopic forms of life.
1735 Carolus Linnaeus classified organisms according to their structural similarities, laying the foundation for modern scientific classification.
Late 1700's Antoine Lavoisier conducted chemical studies of such physiological processes as respiration and the conversion of food to energy.
c. 1800 Baron Cuvier made major contributions in comparative anatomy (the comparison of the structures of different species) and paleontology (the study of prehistoric life).
1838-1839 Matthias Schleiden and Theodor Schwann proposed that the cell is the basic unit of life.
Mid-1800's Gregor Mendel discovered the basic laws of heredity.
1859 Charles Darwin set forth his theory of evolution in The Origin of Species.
Middle and late 1800's Louis Pasteur and Robert Koch firmly established the germ theory of disease.
1953 James D. Watson and Francis H. C. Crick proposed a model of the molecular structure of deoxyribonucleic acid (DNA), the hereditary material in chromosomes.
Late 1970's Researchers used genetically engineered bacteria to produce insulin--a hormone for treating diabetes.
1983 Researchers used genetic engineering to transfer human growth hormone genes into mice, causing the mice to grow to about twice their normal size.
1996 Scientists led by Ian Wilmut achieved the first successful cloning of a mammal from the cells of an adult animal. They produced a clone of a sheep.
Early 2000’s The Human Genome Project and Celera Genomics Corporation, a private firm, completed the sequencing of essentially the entire human genome.