Seemingly random mutations
seemingly??? sorry random mutations is a term used when science has no explanation, completely clueless :)
The "evolution-competition" premise is a half truth... it is not the fittest, not the smartest that survive but the one that is more flexible/adaptable. Generally the fittest and the smartest neglect the flexibility factor and become its victims.
The human species will survive intellectually the day populations realize that Humanity is a body and start developing empathy. The "individual competition dogma" is tearing society apart and paves the way for the next world war and/or total technological enslavement.
I blog a lot about it
Not "fit", as in does a lot of exercise... but "fit" in the sense that it best fits its environment, is better suited or adapted to the environment, as you put it.
for humans it does not work that way... empathy and mental flexibility are key. Competition (theory of the fittest) is antagonist to that. Look at all these ideologies, none will survive. Humans are meant to collaborate peacefully. Voluntarily.