I think that last "would" was supposed to be a "wouldn't"
I meant "we, people without Williams syndrome".
If everyone had Williams syndrome, we wouldn't have a civilisation.
Plausible, but reversal test: there's a saying among certain autistic groups that if there were no autistics, we'd still be gossiping over a raw mammoth leg in a cave. In the everyone-is-an-autie world, maybe AlternateRichardKennaway is saying "If everyone had neurotypicality, we wouldn't have a civilisation". Still, yeah, it's quite possible that we're on average just smart enough for civilisation but no smarter. (Also autism isn't a raw intelligence increase, whereas raw intelligence decreases are common and Williams causes one, so that's another asymmetry.)
Still, yeah, it's quite possible that we're on average just smart enough for civilisation but no smarter.
We evolved to this level of intelligence gradually, not in a single hop. Given that the length of time we have had a civilisation for is pretty much nothing in evolutionary terms, I would guess that we are pretty much exactly at the minimum level of intelligence necessary for a civilisation.
Link: abcnews.go.com/Health/friendly-extreme-meet-kids-adults-williams-syndrome/