Zoology
History

The history of zoology traces the study of the animal kingdom from ancient to modern times. Prehistoric people needed to study the animals and plants in their environment to exploit them and survive. Cave paintings, engravings and sculptures in France dating back 15,000 years show bison, horses, and deer in carefully rendered detail. Similar images from other parts of the world illustrated mostly the animals hunted for food and the savage animals.

The Neolithic Revolution, which is characterized by the domestication of animals, continued throughout Antiquity. Ancient knowledge of wildlife is illustrated by the realistic depictions of wild and domestic animals in the Near East, Mesopotamia, and Egypt, including husbandry practices and techniques, hunting and fishing. The invention of writing is reflected in zoology by the presence of animals in Egyptian hieroglyphics.

Although the concept of zoology as a single coherent field arose much later, the zoological sciences emerged from natural history reaching back to the biological works of Aristotle and Galen in the ancient Greco-Roman world. In the fourth century BC, Aristotle looked at animals as living organisms, studying their structure, development and vital phenomena. He divided them into two groups: animals with blood, equivalent to our concept of vertebrates, and animals without blood, invertebrates. He spent two years on Lesbos, observing and describing the animals and plants, considering the adaptations of different organisms and the function of their parts. Four hundred years later, Roman physician Galen dissected animals to study their anatomy and the function of the different parts, because the dissection of human cadavers was prohibited at the time. This resulted in some of his conclusions being false, but for many centuries it was considered heretical to challenge any of his views, so the study of anatomy stultified.

During the post-classical era, Middle Eastern science and medicine was the most advanced in the world, integrating concepts from Ancient Greece, Rome, Mesopotamia and Persia as well as the ancient Indian tradition of Ayurveda, while making numerous advances and innovations. In the 13th century, Albertus Magnus produced commentaries and paraphrases of all Aristotle's works; his books on topics like botany, zoology, and minerals included information from ancient sources, but also the results of his own investigations. His general approach was surprisingly modern, and he wrote, "For it is of natural science not simply to accept what we are told but to inquire into the causes of natural things." An early pioneer was Conrad Gessner, whose monumental 4,500-page encyclopedia of animals, Historia animalium, was published in four volumes between 1551 and 1558.

In Europe, Galen's work on anatomy remained largely unsurpassed and unchallenged up until the 16th century. During the Renaissance and early modern period, zoological thought was revolutionized in Europe by a renewed interest in empiricism and the discovery of many novel organisms. Prominent in this movement were Andreas Vesalius and William Harvey, who used experimentation and careful observation in physiology, and naturalists such as Carl Linnaeus, Jean-Baptiste Lamarck, and Buffon who began to classify the diversity of life and the fossil record, as well as studying the development and behavior of organisms. Antonie van Leeuwenhoek did pioneering work in microscopy and revealed the previously unknown world of microorganisms, laying the groundwork for cell theory. van Leeuwenhoek's observations were endorsed by Robert Hooke; all living organisms were composed of one or more cells and could not generate spontaneously. Cell theory provided a new perspective on the fundamental basis of life.

Having previously been the realm of gentlemen naturalists, over the 18th, 19th and 20th centuries, zoology became an increasingly professional scientific discipline. Explorer-naturalists such as Alexander von Humboldt investigated the interaction between organisms and their environment, and the ways this relationship depends on geography, laying the foundations for biogeography, ecology and ethology. Naturalists began to reject essentialism and consider the importance of extinction and the mutability of species.

These developments, as well as the results from embryology and paleontology, were synthesized in the 1859 publication of Charles Darwin 's theory of evolution by natural selection; in this Darwin placed the theory of organic evolution on a new footing, by explaining the processes by which it can occur, and providing observational evidence that it had done so. Darwin's theory was rapidly accepted by the scientific community and soon became a central axiom of the rapidly developing science of biology. The basis for modern genetics began with the work of Gregor Mendel on peas in 1865, although the significance of his work was not realized at the time.

Darwin gave a new direction to morphology and physiology, by uniting them in a common biological theory: the theory of organic evolution. The result was a reconstruction of the classification of animals upon a genealogical basis, fresh investigation of the development of animals, and early attempts to determine their genetic relationships. The end of the 19th century saw the fall of spontaneous generation and the rise of the germ theory of disease, though the mechanism of inheritance remained a mystery. In the early 20th century, the rediscovery of Mendel's work led to the rapid development of genetics, and by the 1930s the combination of population genetics and natural selection in the modern synthesis created evolutionary biology.

Research in cell biology is interconnected to other fields such as genetics, biochemistry, medical microbiology, immunology, and cytochemistry. With the determination of the double helical structure of the DNA molecule by Francis Crick and James Watson in 1953, the realm of molecular biology opened up, leading to advances in cell biology, developmental biology and molecular genetics. The study of systematics was transformed as DNA sequencing elucidated the degrees of affinity between different organisms.
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