Paternal Effects in Mammals: Challenges and Opportunities

Once considered heretical, the idea that environmental conditions experienced in one generation can influence traits in future generations is now increasingly accepted. In particular, hundreds of studies in mammals have documented effects of various paternal exposures on offspring metabolism, behavior, and disease susceptibility. While the core claim that a father's experiences can modulate offspring health and disease is now well-established, the mechanistic basis for paternal effects in mammals remains obscure despite nearly two decades of intensive investigation. Here, we briefly review the phenomenology of mammalian paternal effects in broad strokes, focusing on common themes across the literature. We then critically explore our current understanding of the sperm epigenome and discuss challenges to the dominant mechanistic hypotheses proposed in the paternal effects literature.