I didn't downvote you.
But, I'm not saying that humans haven't learned anything, but that cognitively we haven't changed. A roman citizen has the exact same brain capacity to reason and adapt as we do today. There is zero separation from ancient human vs. modern human in that aspect.
You are conflating collective knowledge with individual human intelligence. That roman looking at bird entrails to predict the future was using the exact same pattern-recognition ability we use today to look at data visualizations, or trend graphs.
You could go back in time, steal an ancient roman baby, and raise them in today's year and they would be no different from you or I.
Yes, of course that's right. But I thought you were the one conflating collective knowledge with individual human intelligence, when you said "behaviorally". Behaviors being due to ideas, not nature (I don't much rate nature's effect on smarts anyway).
Maybe I need to spell this distinction out next time it comes up, which will be the next ancient history thread, probably. I guess the endless repetition of "they were just as smart as we were you know!" is in order to counteract an unstated idea that the ancients were some other species, like orangutans in bronze armor, I don't know. Maybe it's common to vaguely think that about them? But this gratuitous counter-point should be on a strictly genetic basis, or else you'd be accidentally denying that ideas improve.
I agree with the "steal an ancient roman baby" premise. The "roman citizen" example is not as strong. Cognitive ability is not just genetics. The grown-up roman would be missing a lot of advantages during their upbringing that weren't available back then. Also, limiting it to just "citizens" means limiting it to their upper class.
Compared to Roman times, we've had pretty big advances in nutrition, healthcare, education, and widespread middle class wealth. It's not unreasonable to infer that these would have an impact on cognitive ability similar to the effect they've had on life expectancy.
That being said, there's definitely a present-ist bias, as the McSweeney's article does a good job mocking. I do believe their best thinkers were as good as our best thinkers.