Menstrual synchrony claims among Suri girls (Southwest Ethiopia) ; between culture and biology

Among the Suri agro-pastoralists, a relatively self-sufficient and independent people of ca. 34 thousand in the extreme southwest of Ethiopia, young adolescent girls often assert that they menstruate together and regulate their own menstrual cycle, relating it to the phases of the moon. "Menstrual synchrony" is a much debated and still unresolved phenomenon in the scientific literature. Rather than giving immediate credence to its existence, I claim that the young, unmarried Suri girls-well aware of all biological facts around procreation, the fertility cycle and pregnancy prevention-follow a cultural script of sexuality and aim to fit physiological facts into a preferred socio-cultural mould. They use the synchrony assertion to change behaviour and thereby to maintain sexual independence and choice of partners in a society that is marked by significant gender equality but also by individual competition. After a brief presentation of key issues in the (inter-disciplinary) debate on menstrual synchrony and its possible existence and causes, I describe Suri sexual culture and menstrual customs, using field data gathered in two villages. I then tentatively assess the plausibility of the Suri girls' claims to menstrual synchrony, and elaborate an interpretation of Suri female sexual/reproductive strategies as enhancing women's agency in a society marred by growing internal instability, conflict, and an uncertain future.