Male Births Could Have Led to Dinosaurs’ End

An asteroid may have wiped out the dinosaurs 65 million years ago not only by changing the world’s climate, but also by causing too many of them to be born male, U.S. and British researchers said Tuesday.

If dinosaurs were like modern-day reptiles such as crocodiles, they change sex based on temperature, David Miller of the University of Leeds in Britain and colleagues noted. In crocodilians, turtles and some fish, the temperature at which eggs are incubated can affect the sex of the developing animals. Miller’s team ran an analysis that showed a temperature shift could have led to a preponderance of males. Other studies have shown that when there are too few females, the population eventually dies out.