Ideas of Hippocrates and Aristotle

Earliest writings on the subject of heredity are those of Hippocrates (400 B.C.) and Aristotle (350 B.C.). Hippocrates believed that characters are inherited from parents because reproductive material is handed over from all parts of the body of an individual. A popular example, used in support by him, was elongated head of human race Macrocephali. Hippocrates believed that parents in this race used to fashion the head of a child soon after birth.

Aristotle could not agree with Hippocrates, because this could not explain inheritance of characters like nails, hairs, voice, grey hairs, etc., because most of these are dead tissues and could not have contributed to reproductive tissue. Aristotle also pointed out cases, where children may resemble their grandparents rather than their parents. He believed that reproductive material was not derived from different parts but from nutrient substances meant for different parts and diverted to reproductive path. These nutrient substances would differ depending upon different parts for which they are meant. He also believed that female sex contributed something to define the form of the embryo (like the carpenter's job is not to supply the wood, but to give shape to the wood to form a chair).