I looked back at cognitive aging papers, but I found that there's significant doubt that the longitudinal tests are actually accurate: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4219741/

So I think it's unclear whether the differences are consistent with the Flynn effect.

Regarding whether g is just analytic ability, I think I spoke a bit too imprecisely. g is defined to be a whole range of things and is correlated with all of them (not just "fluid intelligence" as you quoted Peterson as saying). It's clear that our environment, in addition to on average supplying better nutrition, has also become much more demanding of analytic ability, as you say. My question is really: why is that not enough to drive the change in g? Do you have good reason to believe that the correlation between analytic ability and other things is now lower than it used to be?

The whole thing seems rather like an argument from incredulity to me. Maybe we really are just that much smarter, in these ways, than we used to be.