People were also a lot harder back then because life was harder through the entirety of their existence. Obesity was rare, the average level of fitness was much, much higher, and the teens and adults probably showed a bunch of survivorship bias for hardiness because the weakest died during childhood pretty routinely. I suspect environmental conditions that would kill the average diabetic, obese 45 year old today was just a normal summer day to people back then and was well mostly well tolerated.