Arable land and climates comfortable for people tended to have a very large overlap until the the invention of modern irrigation techniques like center-pivot ir

Arable land and climates comfortable for people tended to have a very large overlap until the the invention of modern irrigation techniques like center-pivot irrigation. Before that, you need pretty special conditions to be able to successfully farm in many of the places in discussion. Arable land that isn't habitable for weeks or months out of the year wasn't terribly valuable or sought out.