Mammoths, like their elephant cousins of today, would have been adapted to the warm climate they evolved in. In these climates, an elephant's biggest problem is getting rid of heat -- they do this with their big ears, through which many heat-porting blood vessels circulate. They wave their ears around in the breeze to dissipate that heat.
That perennial elephant problem was reversed for the mammoths once the Ice Ages settled in and "a whole new environment was made" in the Arctic, which had also been warm up until that point in Earth’s history, Campbell said. Now mammoths had to hold in all the heat they could.
"We know that conserving heat became their number-one concern," Campbell told LiveScience.
Mammoths adapted to their new, colder home partly by evolving a "thick, huge pelt," and down-sizing their ears compared with their warmer-dwelling relatives. "Their ears were tiny, like dinner plates," Campbell said, referring to the cold-adapted mammoths.
How other Arctic animals adapted
But Campbell suspected that the mammoths also could have had blood that was better adapted to work in the cold, like many Arctic mammals alive today do.
Other Arctic animals today, such as reindeer and musk-ox, have a "counter-current" blood system. Essentially the blood vessels taking the warm, oxygen-laden arterial blood down into the legs and feet pass very close to the veins carrying colder, venous blood back to be re-oxygenated. The close contact between the two types of vessels allows the arterial blood to pass its warmth on to the venous blood headed back to the heart and lungs. This evolutionary system keeps the warmth in the core of the animal's body and reduces heat loss due to the cold climate, while still allowing the arterial blood to take its oxygen to the extremities.