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.
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Inside Nature's Giants on Channel Four in the UK is remarkable viewing. And good at ramming home the fact that evolution is the best theory for explaining the observed anomalies in animals like the legs in whales or the bad design of the vagus nerve (shown in the giraffe autopsy).
http://www.channel4.com/programmes/inside-natures-giants/4od
Shadowjack;)
"On October 28, 2006, Japanese fishermen captured a four-finned dolphin off the coast of western Japan, and donated the whale to the Taiji Whaling Museum where it is currently being studied. This bottlenose dolphin has an extra set of hindlimbs, two well-formed palm-sized flippers that move and flap like the normal fore-flippers (see Figure 2.2.2). As with other atavistic structures, these limbs are likely the result of a rare mutation that allows an underlying, yet cryptic, developmental pathway to become reactivated. These limbs are prima facie evidence of the dolphin's four-limbed ancestry, as predicted from the common ancestry of dolphins and other land-dwelling mammals"
This is not evidence that dolphins once had 4 legs because it’s got 4 flippers. This is a case where the developmental pathways have gone wrong and in early development the conditions were right for the cells to develop into flippers. Nothing necessarily to do with genes. You can cause disruptions during development and have flies develop legs where antennae are supposed to be. Does this mean flies early ancestors had extra legs on their head? Or extra legs altogether? No. No, it does not.
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