Hungry Moon: A Microbial Mechanism

I have previously proposed that the 30-day reproductive cycle observed across mammal lineages is the ancestral condition that timed conception to lunar phase (Kirsch 2025). During the darkest week of the lunar cycle, the nocturnal shrew-like ancestor of mammals went hungry because she could not forage effectively in low light. Selection favored females that ovulated after each new moon, because they fed throughout gestation and produced healthy offspring. In this paper, I identify deoxycholic acid as the molecule that schedules ovulation in mammals. I speculate that endothermy evolved to sustain this signal.