
This image shows leg bones removed from a humpback whale captured off the coast of Britih Columbia in 1919, including femur, tibia, tarsus and metatarsal. The whale had two symmetrical hind legs, which were over four feet long and covered in normal blubber and skin. There's no doubt that this whale was a rare anomaly, and that its legs were a mutation, but why would a whale possess the genes for making hind legs in the first place? It seems that either whales evolved from four-legged land-dwelling animals, or that God was, let's say, a little sloppy when he magicked them out of thin air.
You can read more about vestigial organs here.
