All good and such, but this dude's forgetting the plague modern humans have proven to be, now imagine the population was not even controlled during the middle ages with the pandemics we suffered, we'd not even be alive now probably, we're barely better than most animals with the pollution we generate even with all our knowledge and he wants to give that life expectancy and numbers to medieval humans that have yet less understanding of the world, it's like giving a nuke button to a monkey, realistically speaking he's becoming humanity's demise. (If he only advances pharmaceutics in that world, obvs)