Except that when you replace "physical strength" with "cognitive strength", you start having sentences that are very obviously false, like this one: "Whereas previously our intelligence determined how much food we ate and how warm and dry we stayed, it now merely determines how well we function in these new surroundings we have crafted for ourselves as our culture has accumulated."
I think that sentence is perfect as-is. Which part do you disagree with?
First of all, pre-civilized humans (and especially our pre-human ancestors) were highly dependent on intelligence for acquiring food, and staying warm and dry. The part before the comma is obviously true.
Second of all, modern humans in civilization do not usually require intelligence to eat and stay warm and dry, just like we don't require strength. Many humans do well because of inheritance, or because of familial support (this one was available to pre-civilized humans too), and some modern humans benefit from society-level support (admittedly a minority). And many many humans need only minimal intelligence to contribute to their economy enough to buy food and shelter.
The only tricky part is arguing that intelligence helps us function today. For some people it helps, for some people it seems to hurt. Was that your complaint?
I guess we need to define precisely what we mean by cognitive strength. Living in the modern world successfully requires you to understand things like understanding interest rates, monthly payments, and logging into your bank website to check the balance on your account. The amount of intelligence required for that is either greater, or we are talking about a different kind of intelligence, than the kind that required you to hunt and find shelter in caves.
No, modern life provably does not require any of those skills in order to stay fed and warm and dry. For example, zero of my cousins (I have two cousins) have ANY of those three skills, and both of them have survived into their thirties. I wouldn't be shocked if one of them had reproduced, in fact (if so, I pity the female involved).
On the other hand, all three of those skills help to "determine how well we function in these new surroundings" of modern culture.
The minimum intelligence requirements to stay fed and warm and dry, in modern society, are far lower today than any time in the history or pre-history of "humanity". Just like with the minimum requirements for strength. This isn't even a claim about social safety nets. Society is just so rich, food is just so cheap, that you can be a pretty crappy contributor, and even so some other smart guy will figure out how to put you to work, to his profit, and give you just enough to live. It's a good time to be a loser. (It's a great time to be a winner.)
(Oh, and also, I happen to disagree that the intelligence required to understand monthly payments or logging into a website is greater than that for reliably hunting or finding reliable shelter. Interest rates, I'm not sure. But this whole paragraph is beside my main point.)
