Sperm competition drives the evolution of suicidal reproduction in mammals

In some marsupial genera but in no other mammals, escalating stress hormones during the breeding season cause immune system collapse and synchronized death after mating in all males (suicidal reproduction). In this paper, we resolve the environmental drivers and adaptive mechanism of sexual selection responsible for the repeated evolution of this surprising and extreme life history strategy in mammals. The strategy of synchronized suicidal reproduction in mammals resulting in male death before offspring are born has often been attributed to altruistic or kin-selected paternal suicide to avoid food depletion. We show that rather than altruism or kin-selection, individual sexual selection leads to apparent self-sacrifice in these genera.