Some animals, like certain insects, spiders, and plants, die immediately after mating. But what about mammals? A new paper shows that the males of certain mouse-like marsupials face imminent death after having sex — an evolved trait that arose on account of extreme promiscuity.
Take a look at the battle unfolding in this remarkable image. It shows the sperm from two related fruit fly species competing inside a reproductive tract. It’s an evolutionary struggle that, as scientists are now learning, often leads to the introduction of entirely new species.
Researchers from Emory University have discovered that fathers with smaller testicles are more likely to be involved in caregiving activities like diaper changes, feeding, and nap time. Brains scans also show higher activity in their reward system. But the study is far from complete in its assessment.