Lets look at this from another angle.
If you look at crocodiles you'll find they have remained essentially the same for millions of years now. If you look that far back into most other animals history you may only find similar creatures which would indicate that change has occurred.
So why have crocs remained the same for so long?
The answer is evolution, they have evolved to a state where they are perfectly developed for their environment and therefore any genetic mutations are either a disadvantage and therefore selected out or neutral (what could you change in a croc that would not be a disadvantage?)
Humans on the other hand, physically we have remained essentially the same for thousands of years now. The difference is we have evolved socially to the point where genetic disadvantages won't stop you from passing your genes on to the next generation.
If this trend continues in humans I would predict that the gene pool would eventually be flooded with "bad genes" and we will devolve.
A little far fetched maybe but look at cystic fybrosis.
Edited by Jonson-Needs_proof, : No reason given.
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