So what if an experiment were performed today that would conclusively show there's no such thing as a gradual change in species caused by "survival of the fittest? Would it shake your "models" in cosmology, the big bang, or your certainty that our ancestors were superstitious bumpkins who wrote superstitious gobbledty gook that had no bearing whatsoever on either reality or history? Would you doubt the intelligence of experts or your own?
First.
It’s called Natural Selection, not “survival of the fittest”.
Natural Selection have to with the change in environments are driving forces for organisms to change - to adapt in the new environmental conditions so the descendants can continue to produce offspring or reproduce.
Survival of the fittest wasn’t part of the framework of Natural Selection Evolution, and as the term was coined by Herbert Spencer, not by Charles Darwin.
Second.
What do evolution of organisms have to do with the Big Bang?
Living organisms are not planets, stars or galaxies. And planets, stars and galaxies are not living organisms.
As
@Astrophile pointed out to you, the Big Bang Cosmology and Evolution are two completely different scientific disciplines.
Even if you managed to refute one of them, hypothetically, that won’t refute the other.
You still don’t understand how Natural Sciences work.