According to the paper's abstract, "We have genetically retrieved, resurrected and performed detailed structure-function analyses on authentic woolly mammoth hemoglobin to reveal for the first time both the evolutionary origins and the structural underpinnings of a key adaptive physiochemical trait in an extinct species. Hemoglobin binds and carries O2; however, its ability to offload O2 to respiring cells is hampered at low temperatures, as heme deoxygenation is inherently endothermic (that is, hemoglobin-O2 affinity increases as temperature decreases).
"We identify amino acid substitutions with large phenotypic effect on the chimeric Î²/Î´-globin subunit of mammoth hemoglobin that provide a unique solution to this problem and thereby minimize energetically costly heat loss. This biochemical specialization may have been involved in the exploitation of high-latitude environments by this African-derived elephantid lineage during the Pleistocene period. This powerful new approach to directly analyze the genetic and structural basis of physiological adaptations in an extinct species adds an important new dimension to the study of natural selection."
The body of the paper is behind a pay-wall.
According to co-author Professor Alan Cooper, director of the Australian Centre for Ancient DNA, "This is true palaeobiology, as we can study and measure how these animals functioned as if they were alive today."
Typical elephant haemoglobin (and human's as well) is very temperature sensitive, becoming more viscous as the temperature drops, making it more difficult to flow in thinner arteries and veins of the extremities and also less able to release the oxygen it contains.
Mammoth blood evolved to lose such temperature sensitivity, thus permitting it to flow as easily through the blood vessels (and release oxygen) in cold climates as in warm ones.
Professor Cooper observed that this method is far from bringing the mammoth back to life, noting that "the experience of cloning shows reproduction needs a mother of the same species to carry the embryo." And there aren't too many mother mammoths hanging around.
This technique does give us insight to how such animals were able to live in the conditions presented to them; and detailed analysis of the DNA may give rise to methods of increasing the cold tolerance of other species, should the genes prove to be transferable.