The evolution last very long. These types of selections does not happen in 1 day or week, but rather couple of thousands of years - depending on what you are talking about..
hopefully that was informational ! :)
No population or organism is perfectly adapted. ... The population or individual does not "want" or "try" to evolve, and natural selection cannot try to supply what an organism "needs." Natural selection just selects among whatever variations exist in the population. The result is evolution.
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