If people today believe this is something that happens to a terrible level, they'd just truly get a mouthful with all the myriad ways in which premodern life killed us and made us sick. The mortality rates for the prehistoric societies and hunter gatherers that the author mentions was absolutely atrocious by modern standards, based on archeological evidence..

The fundamental problem with many of these analyses is that they're basically stating: "things aren't ideal, boo hoo". Being human in a complex world full of threats internal and external, and both natural and artificial, by default will always make us sick as we individually make our choices to make it worse or better where we have any control at all.

How well we mitigate this compared to how well we mitigated it at any time in the past, and how many completely new options we have for mitigation are much more important than bemoaning the essential reality of the situation.

For example, a hunter gatherer could only do so very little to change any aspect of their diet, daily living habits or basic survival needs. Inside that range was their life and their death. An average modern human, saturated by junk food that their body isn't adapted to handling well, canon the other hand at any time completely remake their diet into something entirely new, or change their career, or take up all kinds of different exercise and sleep options.