alt Hacker NewsI 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.
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Well no, not even as good. For instance, your comment invokes the idea of prejudice, and the value of being unprejudiced. Did Romans know about that, and consider it important? Maybe, I couldn't say offhand, but my point is that they might not have had some valuable idea like that. I think we can say with certainty that they must have lacked some idea of great value to thinking. That makes the ancients all worse at thinking, all of them. This doesn't of course mean that their best ideas were bad though!
Same religions. Same political structures. Same engineering - we've only recently duplicated their concrete, and man, could they build roads and aqueducts. Yeah, they had a dodgy number system, but they had military and political organizations that lasted 1000+ years. They had worldwide trade, and unified far more territory than anybody today.
Life expectancy didn't change that much, what changed is infant mortality.
And for cognitive ability: plenty of firsthand accounts from Enlightenment thinkers about thesuperior reasoning abilities of average members of hunter-gatherer/American Indian tribes compared to the typical European at the time, and they arguably already had better access to nutrition/education/healthcare.
Cognitive ability is for sure related to some extent to these factors, but actual practice of reasoning (through public debates, leisure time, storytelling) seems to have been much more influential on the actual realisation of cognitive potential, and I'm not sure there'd be a stark difference between a typical human today, or even a typical Westerner, vs a typical Roman citizen.