Co-Evolution Blues

OK. Here's the depressing truth nobody seems to be saying.
There's this thing called co-evolution. The concept applies to species. I.e.: The more wiley the coyote, the faster the roadrunner. Generation after generation, coyotes get wiley-er, roadrunners get faster. They evolve together.
Obviously, what applies to species applies also to corporations, religions, philosophies, governments, pretty much anything. Terrorists included.
To cut to the chase ...
If we kill or demoralize 90% of the terrorists, the 10% who survive will be smarter, meaner, more adaptable, more ruthless, just plain better. Thus ...
Our war on terror is breeding better terrorists.
Hell, we beat Al Qaeda. Now there's this thing called ISIS.
The terrorist equivalent of antibiotic-resistant tuberculosis.
It we kick their ass, the 10% that adapt and survive will be ... obviously ... not much fun.
Sitting back, doing nothing and letting the bastards consolidate a Caliphate doesn't seem to be a solution.
I don't have a damn solution.
Just the blues.