Question

Polar bears are white in colour because it refracts white light,but many years ago bear was brown in colour, then how the bear was brown that time but white in colour now?

Answer 1

It is the evolution of polar bear

The polar bear has evolved over time from the common brown bear by changing its fur colour to white, the ideal colour to blend in with its ice-covered surroundings. With new data an international research team now documents that the separation from the brown bear into an independent species has gone very quickly.
changes in the genes have led to changes in the fur colour from brown to white, a natural selection has led to changes in the genes that regulate the transport of fat in the blood and the breakdown of fat in the body.