From Myth to Science. A Short Survey on Heredity and Its Causes in Ancient Greece

In this contribution, I deal with the notion of “cause” concerning hereditary diseases in ancient Greece. A notion of hereditary disease is already foreshadowed in myths, where guilt is often depicted as a pathologic contamination (miasma) affecting both the individual and his offspring (ghenos). The notion of miasma especially concerns diseases whose signs are not visible: in such cases, either gods or maleficent daemons were believed to harass human beings and inflict them punishments that took the shape of diseases. Contamination mainly spreads itself by means of blood-shedding: the slaughter of kinsmen (especially the murder of one’s parents) was widely considered as a main cause of mania (for instance, in Aeschylus’ Oresteia). The Hippocratic treatise On the Sacred Disease traces the boundaries between science and the notion of the daemonic origin of diseases, even if both are presupposed by some Vth century authors (for instance, Herodotus). In the Hippocratic medicine, humours seem to be the actual vehicle of heredity, while on the other hand, likenesses between parents and children find an explanation in the doctrines of bisexual semen and panspermia (De genitura pueri). Therefore, some features of both parents can be found in their children, and affect their health as well. This explanation is no longer acceptable if the existence of a female semen is denied, as by Aristotle (De generatione animalium). For Galen (De semine), likenesses between children and parents are due to the prevalence either of the father’s semen, or the mother’s one, when female and male semen mix together in the womb. The mixture will cause the likeness of each part in the child’s body to the parent whose semen is prevalent. On the other hand, the development of the embryo is strongly dependent on the parents’ conditions, and on diseases affecting the mother’s womb.