Last year, Colossal Biosciences claimed to have revived a species that became extinct 10,000 years ago. The company bred three pups, Romulus, Remus, and Khaleesi, whose cells contained bits of DNA—units of hereditary material—that match the DNA of the ancient dire wolf.
Colossal used a DNA-editing technology called CRISPR to replace sections of DNA in the cells of modern gray wolves with copies of dire wolf DNA. In the past, scientists had used CRISPR to make only two or three edits to DNA at once. But Colossal made a total of 20 edits! These changes produced pups with bigger paws and thick, white fur. Their skulls are also larger than those of most gray wolves.
But according to geneticists, these alterations don’t make the pups dire wolves. Anders Bergström, from the University of East Anglia in the United Kingdom, is one of these critics. “These are gray wolves that look slightly different,” he says.