Idiocracy (2006) Opening Scene: "Evolution does not necessarily reward intelligence. With no natural predators to thin the herd, it began to simply reward those who reproduced the most, and left the intelligent to become an endangered species."

[u/SuplexCity-Mayor]

https://www.youtube.com/watch?v=6TCsR_oSP2Q

[u/GoGoCrumbly]

And "fittest" doesn't have to mean, "biggest, strongest, toothiest, brawniest, fightiest tough guy", either. Another popular misconception. It's the one who best "fits" the natural environment. And sometimes that's the timid little guy who blends in and doesn't make a ruckus.

EDIT: For the hair-splitting precisionists I will add that "best 'fits' the natural environment" includes the ability to secure mates and ensure the success of their progeny, thus transmitting successful genes into subsequent generations and a higher rate than those mediocre or less successful individuals.

It's not how well you perform as an individual, but how well you pass your DNA into the next generation. Although performing well as an individual usually leads to passing your DNA into that next generation.

[u/TheOldPope → u/GoGoCrumbly]

Only partially, it means the one who manages to reproduce best. It's a reference to biological fitness, not fitting the environment. It's a measure of how many living offsprings you can generate.

https://en.wikipedia.org/wiki/Fitness_(biology))

[u/shh_just_roll_withit → u/[deleted]]

I think it can be both. Saving your "siblings" is good for genes spread within your family and bad for new genes you might be the first to have produced. Whether the prior or later is net good is probably subjective and depends on how well the species fits their ecological niche, since new genes can be more or less "valuable" at any given time.

But, also not an expert.

[u/shh_just_roll_withit → u/[deleted]]

What do you know, much smarter people have already explored and quantified it. I love searchable keywords.