Why are some mutations, like additional limbs or more than 50 chromosomes, are just not possible for humans to have?
In: Biology
Evolution works by making small changes over time. It would be theoretically possible for humans to have additional limbs or 50 chromosomes, but there would be a transition period over thousands of generations where humans developed a bud, over a few more thousands of generations, the bud grows out more. A thousand more, the bud develops muscles that allow it to move a bit. After millions and millions of years you might have what you could classify as a limb.
[A classic example that demonstrates the limitations of evolution is the eye.](https://www.youtube.com/watch?v=Nwew5gHoh3E) Our eyes, and the eyes of all land animals are filled with fluid. If it were to be filled with air instead, it would be able to see strictly better. That was too big of an evolutionary jump for the sea animals transitioning to land to make though. They had water filled eyes, which saw blurry on land at first but were able to incrementally adapt them to see better on land over generations. Any mutation that ditched the fluid for air would still have lens that are meant for being fluid filled, and so would be a step backwards in vision. They’d have to somehow miraculously ditch the fluid *and* focus for air, which is just too far fetch to ever happen.
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