I mean suppose the genome of a species has about a million sites where a change of a single nucleotide could yield an advantage by natural selection. And these sites are spread through some ten thousand genes that each encode some ten thousand proteins. So there would have to be a hundred potential adaptive changes that could occur in each of ten thousand genes. This all means that any given species must have a lot of freedom in the way it evolves.
Not that much, because you're ignoring natural selection.
I recently wrote a computer program where what evolves are two-dimensional shapes. The selective criterion was maximizing area divided by perimeter.
Each time I ran the program, the initial shape was random, the mutations were random ... but the end result was
always a perfect circle. Because the selective pressures were
not random and were the same in every case, every simulated population converged to exactly the same shape. This is not surprising or unlikely; it is inevitable.
Really, if you can't figure out this sort of thing on your own you need to get an introductory text on evolution and start again from the beginning.
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