CURWOOD: It's summer! Time to celebrate and visit some of the new national parks and monuments in America. But first this note on emerging science from Poncie Rutsch.

RUTSCH: For years, scientists have looked at sea turtles and wondered, “Who’s your daddy?”

Tracing paternity in turtles is tougher than you might think. First, there’s very little research on male turtles - since they don’t lay eggs, they rarely come ashore, and so scientists seldom get a chance to test their DNA.

Second, sea turtles don’t have sex chromosomes, so it’s hard to distinguish mom DNA from dad DNA. Instead, the egg’s temperature during incubation determines whether it will hatch into a male or female. The warmer eggs tend to be female, and since climate change is warming tropical beaches, scientists thought that females probably outnumbered males in the ocean.

Now, sea turtle scientist Peter Dutton knows that that’s not the case. Dutton and his colleagues at NOAA managed to separate out paternal DNA and found that sea turtle populations had much greater genetic diversity than they’d predicted, indicating that sex ratios are most likely evenly balanced.