Who says it doesn't evolve, Juven? Anything I've seen from science makes it clear that animal intelligence definitely does evolve. The higher on the scale, the more intelligent.
That is the correct evolutionary answer.
But many similar questions can be asked.
Why don; t we see any improvements in the survivability of organisms that dated very old based on naturalistic fossil interpretation and still live today?
The millions of years should have caused numerous mutations.
The evolutionists see it like this:
Every random mutation is a step in a direction.
There are numerous directions it can go to.
Numerous possibilities, every mutation represents / is one of the possibilities.
It can go in all directions.
It
could be (the "chance" component of the theory) a step in the direction of development (good direction).
That is a step towards a beneficial characteristics,
therefore it is the better organism than the one without the mutation,
therefore it will survive natural selection.
And this is how organisms gradually become what we would call ''another species", developing towards specialized creatures who find their niche in the eco system.
After billions of years, you get living nature as we know it today, because steps in the good directions will dominate.
Do i have to point out the fallacies?