That's one of my fun speculations for the drop in sperm fertility. There's less violence in the world; men spend far less of their time practicing and preparin

That's one of my fun speculations for the drop in sperm fertility. There's less violence in the world; men spend far less of their time practicing and preparing for war. So, as well as the concomitant lack of physical exercise (which almost certainly plays a part) there is something in our biological makeup which says since there is less danger, there is less need to procreate.