Using ancient DNA preserved in bones from Siberian mammoths 25,000 to 43,000 years old, scientists have brought the primary component of the specimens' blood "back to life."

The seven-year research effort, detailed this week in Nature Genetics, reveals special evolutionary adaptations that allowed the mammoth to cool its extremities down in harsh Arctic conditions to minimize heat loss.

The findings will also help scientists study the DNA of other extinct species, such as Australian marsupials.

This is the structural model of the mammoth hemoglobin, with the three key changes to the protein highlighted in red.

(Photo Credit: Illustraton by Ansgar Philippsen)

"We've managed to uncover physiological attributes of an animal that hasn't existed for thousands of years," says team leader Professor Kevin Campbell of the University of Manitoba, Canada. "Our approach opens the way to studying the biomolecular and physiological characteristics of extinct species, even for features that leave no trace in the fossil record."

The team converted the mammoth hemoglobin DNA sequences into RNA, and inserted them into modern-day E. coli bacteria, which then manufactured the authentic mammoth protein. "The resulting hemoglobin molecules are no different than 'going back in time' and taking a blood sample from a real mammoth," says Professor Campbell.

Researchers also used modern scientific physiological tests and chemical modeling to characterize the biochemical properties that confer mammoths with physiological cold tolerance.

Team member Professor Roy Weber of the University of Aarhus, Denmark says the findings help show how the mammoth survived the extreme Arctic cold.

"Three highly unusual changes in the protein sequence allowed the mammoth's blood to deliver oxygen to cells even at very low temperatures, something that indicates adaptation to the Arctic environment."

Citation: Campbell et al., 'Substitutions in woolly mammoth hemoglobin confer biochemical properties adaptive for cold tolerance', Nature Genetics, May 2010; doi:10.1038/ng.574