The beavers began to fell trees to build dams, but for the sake of power, reported in Scientific Reports. Talking about this features of the structure of fossil rodents, as well as the content of stable isotopes carbon-13 and nitrogen-15 in bone collagen of prehistoric beaver of the genus Dipoides and plants that lived at the same time (about four million years ago) in the same area (the canadian island of Ellesmere). The researchers believe that creating dams and lodges, as well as to store in the shed branches the beavers began in response to cold, although the first semi-aquatic beavers didn’t do it.
Now there are two kinds of beavers (family Castoridae) European (common) Castor fiber and canadian Castor canadensis. They both have solid for rodents dimensions — weight from 12 to 25 pounds, occasionally up to 40. Such large animals with its powerful tools, easily felled trees and stems of their trunks and branches of the river. In addition, the branches serve as beavers building material for homes, lodges, and food.
However, that was not always the case. Probably now extinct semi-aquatic beavers do not build dams and houses. Limited evidence that they actually gnawed trees, occurring from the location of the beaver pond on the canadian island of Ellesmere. There are about four million years ago, there were beavers of the genus Dipoides. Paleontologists found there small branches with traces of incisors of the animal, which in size was consistent with the fossil beaver (from its bones Dipoides, he was about a third smaller than the modern representatives of their families).