By inserting a 43,000-year-old woolly mammoth gene into Escherichia coli bacteria, scientists have figured out how these ancient beasts adapted to the subzero temperatures of prehistoric Siberia and North America. The gene, which codes for the oxygen-transporting protein hemoglobin, allowed the animals to keep their tissues supplied with oxygen even at very low temperatures. “It’s no different from going back 40,000 years and taking a blood sample from a living mammoth,” says Kevin Campbell, a biologist at the University of Manitoba in Canada.