Concepts of inheritance in Graeo-Roman times
The earliest genetic concepts arose from the mists of antiquity. In the 6th century BC the so-called Pre-Socratic Greek philosophers started to postulate concepts based on the assumption that hereditary factors from mother and father were transferred to the child via the male and female semen (or semen equivalent). The Hippocratic doctors (5th and 4th centuries BC) consolidated existing wisdom by way of a complex theory which stated that hereditary factors (sex and general characteristics) transferred via male and female semen, determined the appearance of the child, but only after modifying factors such as volume, consistency and origin of semen, the elements heat, cold, moistness and dryness, and the position of foetus in the uterus, had played a role. Aristotle (4th century BC) postulated a very different theory, based on the assumption that the male was superior to the female, and that his strong semen would determine the hereditary process. Ideally this would lead to the birth of a male child, resembling his father. It was, however, possible that due to factors such as a strongly ‘concocted’ (enriched) female generative substance (menstrual blood, as she had no semen), specific weather conditions, the age of and interaction between parents, as well as the type of water drunk, the male dominance could be qualified, resulting in a sub-ideal child - e.g. a male child with the mother’s characteristics, or even a female child. Subsequent philosophers and physicians including Galen (2nd century AD), added little new to these two main doctrines, and Roman writers in particular tended to introduce elements of mysticism and superstition.