Rudyard Kipling imagined in his Just So Stories that the camel got its hump as a punishment for an idleness. And, as it turns out, the real reason is almost as unlikely.
Rather than being a natural device for storing water in the desert as many believe, the hump was originally developed to store fat in polar conditions, according to scientists.
Thirty fossilised pieces of a lower leg bone belonging to a camel which lived 3.5?million years ago were found by researchers on Ellesmere Island, in the north of Canada.
The giant mammals would have measured up to 11ft in height and had one hump in which they stored fat to help them survive in the winter, at a time when the region was less cold than today and covered with forest, researchers said.
It has been known for many years that camels' humps are reservoirs of fatty tissue, as opposed to stores of water as was once commonly believed. The evolutionary adaptation allows them to thrive in hot climates because storing fat on their back minimises the insulating effect it would have if distributed over the rest of their bodies.
Dr Natalia Rybczynski of the Canadian Museum of Nature said: "Perhaps some specialisations seen in modern camels, such as their wide flat feet, large eyes and humps for fat may be adaptations derived from living in a polar environment."
Analysis of the fragments of tibia, or lower leg bone, showed that it belonged to a family of cloven-hoofed animals known as arteriodactyls, the ancient forerunners of today's cows, pigs and camels.
The bone dates back to a time when the Earth was warmer and the Arctic, though still cold, would have been home to forests of poplar, birch and conifers.
During that period the largest arteriodactyls were camels, suggesting that the bones belonged to an ancestor of the modern desert-dwelling species.
Camels were already known to descend from giant forerunners in North America, but the discovery provides the first evidence that they lived at such extreme latitudes.
Previously fossils had only been found at least 750 miles further south than the new discovery, researchers explained in the Nature Communications journal.
The finding was confirmed by experts from Manchester University who analysed tiny remnants of collagen, a protein found in bones, and compared it against 37 modern species of mammal as well as the fossils of a giant camel from further south in Canada's Yukon province.
The new fossils' collagen closely matched that of modern camels, particularly one-humped "dromedaries", and the Yukon giant camel.
Dr Rybczynski said: "This is an important discovery because it provides the first evidence of camels living in the High Arctic region.
"It extends the previous range of camels in North America northward by about 1,200km, and suggests that the lineage that gave rise to modern camels may have been originally adapted to living in an Arctic forest environment."