Life in a cold climate

How do animals and people manage to live in the Arctic? Ask Karl Georg Christian Bergmann (1814-65). This German medic and anatomist worked out that as conditions get colder, animals get bigger.

In the US, a much-studied example of Bergmann's Rule is the Song Sparrow. Members of this widespread species that live by the sea are smaller than the ones found in the mountains. The logic is simple. As the animal gets bulkier, it has more cubic centimetres of innards for every square centimetre of surface, so it holds the heat in that much better.

With humans such as the Inuit, Bergmann's Rule applies along with Allen's Rule (Joel Allen, 1838-1921), which states that warm-blooded creatures living in colder environments have shorter appendages, again to save heat loss. So the Inuit are stockier and shorter of arm and leg than Africans. They also have other physical adaptations. They have layers of insulating fat round the heart and other vital organs. And they have a faster metabolism than other races, to keep them warm.

But these adaptations exist alongside an equally important range of artificial measures which are deeply embedded in polar-dweller culture. They have developed homes that stay warm through the long Arctic night. Long before Gore-Tex, and far away from the nearest sheep to provide wool, they developed boots, coats and hoods that keep people dry as well as warm. Living and sleeping en masse, perhaps for months at a time, is second nature. And travellers have noted that just as Africans are expert at finding a bit of shade, so Inuit will find a way of standing in the sun any time it comes out.