Dropped a line in above. I'm assuming a normal distribution of intelligence from a nature perspective that has not changed much in the last 2k years, and then on top of that an enormous nurture influence.
Right now there are a lot more people, with a lot more access to reading and writing education, and food - than there have been in the past. 90k legal graduates/y is a huge output. If you assume the filters that put folks into clerkship are a mix of meritocracy and then some elbow-rubbing noise - the end outcome should still be extremely talented compared to other groups of thinkers in the past. This does also imply that the same should be true for other current intellectual institutions that filter from large pools.
The assumption breaks down to the extent the filters aren't meritocratic. I'm not super qualified to speak to that - and there's at least one qualified opinion above expressing that the mix maybe leans more towards work and networking than ability - so maybe I'm wrong here.