Detrimental just means "negative", at any level.
Jumping off a building is detrimental to your health.
But so is smoking a single cigarette.
They're detrimental to vastly different degrees, but they both impart at least some negativity, so you can call either one detrimental.
If future progress depends on restoring the balance between assertiveness/combat and nurturing/cooperation via more nurturing/cooperation, then assertiveness/combat is detrimental (has at least some negative effect) on progress.
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In regards to (E), I'll admit I'm confused about it too. I think it's too supported an answer to be wrong, even though it is definitely a recklessly strong-worded answer to pick on LSAT.
Maybe you're right that they see a gap between "continuation of the process" vs. "progress in relation to the process". I just have a hard time believing that because the process we're talking about is
evolution. Can you continue the process of evolving and not call that progress?
But I think that is what they were going for: a disconnect between saying in the passage that "X would be required for Y to happen" and saying in the answer "continuing the process of striving for Y will lead inevitably to X".
The passage is trying to say, "in order to get somewhere BETTER with evolution, we'd NEED to have cooperation/nurturance",
and the answer is saying, "as we continue evolution, we are GUARANTEED of getting better (i.e. of having cooperation/nurturance)"
I think we're getting bogged down in a literal definition of 'progress', which could mean anything ... advancing to the next day / next year / next decade, and a figurative definition of 'progress', which would mean 'reaching a BETTER place'.
If we interpret Gilman's comments as saying, "in order to get to a BETTER PLACE, we'd need X",
then we can reject (E) by saying, "as we continue to evolve, there's no guarantee we'll get to the better place".