My animation will focus on whale evolution and particularly how modern whales still have vestigial limbs left behind in their evolved bodies. The animation will tell the story in 1 minute of how the most ancient whales (eg Basilosaurus) evolved into modern whales but kept their hind limbs.
I think perhaps i will go into more depth about the evolution and the proof that is out there by looking further into skeletal structure. (5 fingered hands and flippers and paws)
Biologists believe that for 100 million years the only vertebrates on Earth were water-dwelling creatures, with no arms or legs. At some point these ?fish? began to develop hips and legs and eventually were able to walk out of the water, giving the earth its first land lovers. Once the land-dwelling creatures evolved, there were some mammals that moved back into the water. Biologists estimate that this happened about 50 million years ago, and that this mammal was the ancestor of the modern whale. Despite the apparent uselessness, evolution left traces of hind legs behind, and these vestigial limbs can still be seen in the modern whale. There are many cases where whales have been found with rudimentary hind limbs in the wild, and have been found in baleen whales, humpback whales, and in many specimens of sperm whales. Most of these examples are of whales that had only leg bones, but there were some that included feet with complete digits. It was reported recently that whales and hippos were distantly related.
There's a couple reasons why the protruding hind limbs occasionally found in modern whales don't have anything to do with a proposed quadruped ancestor.
ReplyDeleteThey are simply Hox gene mutations where the genetic code for the front limb is accidentally expressed in the hind region.
This is evident if you examine the historical cases - and even the investigators remark at the similarities between the front flipper and the hind protrusion.
If these were a reversion to an ancient growing pattern, the femur bones would actually grow deeper into the body, not out of it - because in modern whales, the femur bone points towards the center of the body.
The other problem is that the femur bones have novel tendon connections that anchor them to abdominal muscles (something not at all found in any proposed ancestor).
These novel muscular and tendon connections would prohibit the bones from growing outwards from the body.
These cases of hind protrusions have simply been glossed over and harnessed to try and prove a point they have nothing to do with.