My impression is that the sperm are optimized for a brief period of super activity at normal human body temperature. This enables them to reach the egg once ins

My impression is that the sperm are optimized for a brief period of super activity at normal human body temperature. This enables them to reach the egg once inside a woman's body. If they become adapted to this higher temperature then what would kick them into a brief overdrive and burnout? Perhaps some chemical signal could be secreted to triger them, but that means two beneficial mutations have to happen at the same time. This makes it far less likely and perhaps only strong selective pressure, as in seals, could bring out this double adaptation.