Mating Effort Predicts Human Menstrual Cycle Frequency.

The human menstrual cycle is characterized by substantial variability both within and between women. Here, we sought to account for such variability by examining whether human menstrual cycle frequency varies as a function of the projected fitness payoffs associated with investment in mating effort. We used structural equation modeling to test the prediction that women whose environmental conditions or life histories favor heavier investment in mating effort would have shorter, more regular cycles. Results supported our hypothesis, revealing that women who project more mating success and have faster life history strategies exhibit greater mating effort and shorter, more regular menstrual cycles. An alternative model that specified cycle frequency as a predictor of mating effort was a poor fit for the data, lending support for the hypothesized directionality of the path between these variables. Together, these results provide some of the first empirical evidence that the length and regularity of the human menstrual cycle may be calibrated to investment in mating effort.