The U.S. Department of Health and Human Services issued guidance updating its official definitions of terms such as sex, ...

A recent Trump executive order defines sex based on gamete size. But the order oversimplifies genetics, hormones and reproductive biology.

Divers don't all look the same to fish. If they get food from a person, they will recognize them next time and follow them persistently. Less generous divers, on the other hand, tend to be ignored, as ...