Yeah, but the "fitness testing" would take way more than 10 minutes. http://en.wikipedia.org/wiki/John_Koza had run this type of experiments (not in cryptocurrency though).

By itself Bitcoin's "chain with the highest sum of proof-of-works" will tend to favor fastest functions, not the best hash functions. Somebody with heavily optimizing compiler, SAT-solver or similar optimization tool could then exploit such coins that don't extensively test the evolved hash functions.