THE RETURN OF THE DIRE WOLF

FOR THE FIRST TIME, SCIENTISTS SAY THEY'VE SUCCESSFULLY BROUGHT A SPECIES BACK FROM EXTINCTION. THAT HAS BIG IMPLICATIONS FOR ENDANGERED ANIMALS

- - BY JEFFREY KLUGER

ROMULUS AND REMUS ARE DOING WHAT PUPPIES DO: chasing, tussling, nipping, nuzzling. But there’s something very un-puppylike about the snowy white 6-month-olds—their size, for starters. They already measure nearly 4 ft. long, tip the scales at 80 lb., and could grow to 6 ft. and 150 lb. Then there’s their behavior: the angelic exuberance puppies exhibit in the presence of humans—trotting up for belly rubs and kisses—is completely absent. They keep their distance, retreating if a person approaches. Even one of the handlers who raised them from birth can get only so close before Romulus and Remus flinch and retreat. This isn’t domestic canine behavior, this is wild lupine behavior: the pups are wolves. Not only that, they’re dire wolves—which means they have cause to be lonely.

The dire wolf once roamed an American range that extended as far south as Venezuela and as far north as Canada, but nota single one has been seen in over 10,000 years, since the species went extinct. Plenty of dire wolf remains have been discovered across the Americas, however, and that presented an opportunity for a company named Colossal Biosciences.

Relying on deft genetic engineering and ancient, preserved DNA, Colossal scientists deciphered the dire wolf genome, rewrote the genetic code of the common gray wolf to match it, and, using domestic dogs as surrogate mothers, brought Romulus, Remus, and their sister, 2-month-old Khaleesi, into the world in three separate births last fall and this winter—effectively for the first time de-extincting a line of beasts whose live gene pool long ago vanished. TIME met the males (Khaleesi was not present because of her young age) at a fenced field in a U.S. wildlife facility on March 24, on the condition that their location remain a secret to protect the animals.