It is widely believed among the Marquesans that the best part of the menstrual cycle for achieving conception was the period immediately following the menstrual flow, while the period for avoiding conception was thought to be the days midway between two menstruations. Thus the Marquesans had a clear concept of a "safe period": they just got it all the wrong way round. (R. C. Suggs "Marquesan Sexual Behaviour") It was thought that the male would become impotent if he copulated with a menstruating woman.