History of AnimalsAristotle

Aristotle's History of Animals is the largest surviving work of ancient natural history: ten books cataloguing the structures, habits, and differences of animals across hundreds of species. It is not a theoretical treatise but a systematic collection of observations, organized to support the comparative biology Aristotle develops in his other zoological works.

The early books classify animals by their parts: blooded and bloodless, viviparous and oviparous, terrestrial, aquatic, and aerial. Aristotle describes the anatomy of fish gills, the chambered stomachs of ruminants, the reproductive organs of cephalopods, the social organization of bees. His observations range from the commonplace to the remarkably precise. He correctly identifies that the embryo's heart is the first organ to develop and that some sharks bear live young.

Not everything holds up. Aristotle sometimes relies on secondhand reports, and some claims (spontaneous generation of eels, for instance) are wrong. But the method is sound: observe widely, compare carefully, and let the differences among kinds reveal the principles of organization. Darwin kept the History of Animals close at hand, and the continuity between Aristotle's comparative project and modern evolutionary biology is not accidental.