Surprise Find in Antarctica: Oldest Animal Sperm

They were looking for mammal bones, but scientists exploring an island in the Antarctic instead stumbled across an unexpected milestone—the world's oldest animal sperm. They found it inside a fossilized cocoon made by some type of worm (possibly a crayfish worm) 50 million years ago, reports Nature. It beats by 10 million years the previous record-holder, a specimen from an insect relative called the springtail. “A 50-million-year-old worm sperm from Antarctica?” Benjamin Bomfleur of the Swedish Museum of Natural History marvels to the Washington Post of his team's discovery. “Who would have thought that’s possible?”

These types of cocoons aren't of the butterfly variety but were instead used in the mating process, explains Popular Science. They're secreted by the worms to hold the sperm and egg, and they often trap other things inside as they harden. "That's what makes this research so exciting," writes Mary Beth Griggs. "By taking a closer look at the cocoons, researchers can get a better idea of what kinds of microorganisms were around in the past." Because sperm cells are so delicate, it's rare to find any this old. Still, the age doesn't come close to the oldest sperm on record, reports Live Science. That hails from a plant found in Scotland and goes back 410 million years. (A bioethicist thinks men should freeze sperm samples at age 18.)