This is a skeleton of a blue whale on exhibit at the Beaty Biodiversity Museum on my university campus. Originally, it came from Prince Edward Island. Did you know that blue whales are the largest living mammals on Earth at the moment?
Warning: (A lot of) Science Ahead
One fact that you may not know is that whales used to have legs. That's right, legs! The ancestor of whales lived a largely terrestrial lifestyle. After years and years of evolution, modern-day whales now live a fully aquatic lifestyle. Their front limbs became flippers and they "lost" their hind limbs. Or have they?
Functionally, yes, but evolution is not a perfect process. It is a long, gradual, and continuous process full of chance events that collectively bring about extinction (the end of species) and speciation (the development of new species). There are many clues in organisms that hint at their evolutionary histories. One clue for whales is the presence of vestigial hind limbs. In other words, they have tiny bones in their skeleton that are remnants of what used to be leg bones. That seems inefficient. Biology is all about saving energy and conserving resources. Why would whales bother putting in time and energy to make useless bones for limbs that no longer function?
In truth, it is inefficient and does waste energy. However, as stated above, evolution is a process full of chance events. In evolution, things aren't as simple as just pressing an un-do button. Legs don't just suddenly appear because of one mutation and disappear when that mutation disappears. In the whales' evolutionary history, genetic mutations that slowly built up eventually led to whales not developing any functional legs, but that doesn't mean the process of developing legs was removed altogether. Perhaps the process was damaged or halted very early on during development.
Another similar example can be found in snakes. During embryonic development, many snakes start to form buds for hind limbs. Most of the time, however, they are soon reabsorbed. Some snakes, such as boas and pythons, have vestigial hind limb bones, similar to whales. Again, inefficient, but very cool, in my opinion.
I will stop here. I can elaborate further, but that may make my scientific explanation too long-winded...
PS: As you have probably gathered, I love evolution. :) I took an evolutionary biology class a year ago, and it was one of the most interesting classes I have ever taken. Also, I feel like I may have written about evolution before. Please excuse me if I've repeated anything in this post.
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