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?

Polar bears are white in colour because it refracts white light,but ma

1.	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» 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?