The Bleeding Ledes

[Ken]

Turns out people haven't actually been living in the entire world in large numbers until the invention of air conditioning.

Probably true. I'm just pointing out that it isn't "coastal" that is the most important factor here. Boston, London, Venice, Tokyo are all coastal cities that have existed for centuries but they are all in temperate climates and latitudes. The coastal tropics and subtropics have not been very hospitable places to live due to heat and disease until the modern era. And the Gulf Coast of the US would be included.