The resulting family tree recalibration allowed the researchers to calculate when the two tardigrade lines that perform cryptobiosis could have diverged—putting a latest date on the likely acquisition of that skill. Their work suggests cryptobiosis appeared in tardigrades during the Carboniferous period (359 million to 299 million years ago), predating a deadly event known as the Permian extinction, or the “Great Dying,” which occurred about 252 million years ago. The authors suggest that cryptobiosis may have helped tardigrades survive the event, which wiped out 96 percent of marine life and 70 percent of life on land. {read}