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Human beings have always studied animals. Knowledge of animal behavior was a necessity to prehistoric humans, whose survival depended on their success in hunting. Those early people who hunted to live learned to respect and even revere their prey. The earliest known paintings, located in the Lascaux Caves in France, depict animals, demonstrating the vital importance of animals to early humans. Most experts believe that the artists who painted those images viewed the animals they hunted not just as a food source, but also as an important element of spiritual or religious life.

The first important developments in zoology occurred in Greece, where Alcmaeon, a philosopher and physician, studied animals and performed the first known dissections of humans in the sixth century B.C. Aristotle, however, is generally considered to be the first real zoologist. Aristotle, who studied with the great philosopher Plato and tutored the world-conquering Alexander the Great, had the lofty goal of setting down in writing everything that was known in his time. In an attempt to extend that knowledge, he observed and dissected sea creatures. He also devised a system of classifying animals that included 500 species, a system that influenced scientists for many centuries after his death. Some scholars believe that Alexander sent various exotic animals to his old tutor from the lands he conquered, giving Aristotle unparalleled access to the animals of the ancient world.

With the exception of important work in physiology done by the Roman physician Galen, the study of zoology progressed little after Aristotle until the middle of the 16th century. Between 1555 and 1700, much significant work was done in the classification of species and in physiology, especially regarding the circulation of blood, which affected studies of both animals and humans. The invention of the microscope in approximately 1590 led to the discovery and study of cells. In the 18th century, Swedish botanist Carl Linnaeus developed the system of classification of plants and animals that is still used.

Zoology continued to develop at a rapid rate, and in 1859, Charles Darwin published On the Origin of Species, which promoted the theory of natural selection, revolutionized the way scientists viewed all living creatures, and gave rise to the field of ethology, the study of animal behavior. Since that time, zoologists throughout the world have made innumerable advances.

The rapid development of technology has changed zoology and all sciences by giving scientists the tools to explore areas that had previously been closed to them. Computers, submersibles, spacecraft, and tremendously powerful microscopes are only a few of the means that modern zoologists have used to bring new knowledge to light. In spite of these advances, however, mysteries remain, questions go unanswered, and species remain undiscovered.

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