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.
Plato begs to differ re: philosophy. Ancient people could memorize staggeringly more than folks today. They probably also paid (far) more attention to their surroundings. Like Rangers in D&D, they could read blades of grass and state what/when walked by...
A lot of this is simply due to environment that they live in.
When I was in nautical school, I was taught to always be aware of sea state regardless of where I was/what I was doing so I'd get in the habit of always knowing what the sea was doing.
Now I live on a farm. We are always very aware of the weather and instinctively comparing what we see around us to what the forecasts say.
When I lived in a city, I was barely aware of even if it was supposed to rain later or not. Going from your climate-controlled house to your climate-controlled car, to your climate-controlled job, you simply don't notice those things except superficially.
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.