Earlier this year, a group of researchers published a paper on the remarkable phenomenon of sex reversal in several Australian birds, including wild magpies and kookaburras.

They’ve yet to discover the exact mechanism through which this happens. Nonetheless, their discovery would have fascinated medieval scientists, who were just as engaged in trying to understand sex and gender in the avian world.

Sexual differences in birds include anatomical and behavioural characteristics that vary within and across species.

Scientists have found biological triggers for sex-specific traits that may shift during an individual’s lifetime. For example, female ducks and chickens can take on “masculine” attributes once their egg-laying years are over.

The Greek philosopher Aristotle (384–322 BCE) observed similar changes in birds almost 2,400 years ago. His text History of Animals explained that the physical characteristics of sex in chickens and other animals could change according to action and circumstance.

In medieval Europe, the word “sexus” was used to refer to everything people now label as “sex”, “gender” and “sexuality”.

Research on sexus occurred in all the places of medieval science: schools, universities, monasteries, households, workshops and natural landscapes. Medieval people developed their own experiments and theories based on their lived experiences.

Those who read Latin or Greek studied and revised the findings of ancient authorities such as Aristotle, Galen and........

© The Conversation