“E cussì se fanno homicidiale di proprii fioli”: i parti gemellari tra teorie mediche e implicazioni morali dall'antichità al tardo Medioevo

"E cussì se fanno homicidiale di proprii fioli": twin births between medical theory and moral implications from Antiquity to the late Middle Ages. The essay aims to provide a brief overview of the evolution, continuities and changes of past medical theories related to twins. Although we now understand the causes underlying the birth of fraternal twins, exactly how and why identical twins result from the exact split of one fertilised egg-cell still remains a mystery to embryologists today. We can only guess at how mysterious both these processes must have appeared to our antique, medieval and early modern ancestors, who knew nothing about egg-cells, spermatozoa, and menstrual cycle as specifically linked to reproduction. Special emphasis is placed on the gendered dimension of past understandings of twins, who were often regarded as the by-product of adulterine, illegitimate and immoral women’s behaviour. Women, therefore, were increasingly considered morally responsible, beyond their biological input, for the birth and (often) the death of their twin offspring.