There seem to be some rather dubious assumptions there, notably that hunting is a more efficient way of acquiring nutrition than gathering. I'm not a specialist in the field, but my understanding was the opposite.
And sentences such as "[...] baboons [...] devote almost all their daylight hours to feeding [...] while adult Ache and Hadza men spend only a third of the day in food acquisition, preparation, and feeding"? I probably wouldn't go there…
It's kind of convenient that one of the author appears to be selling an app that has just the right diet for the modern troglodyte: https://nutrita.app/author/raphael-sirtoli/
For prehistoric nomads hunting would definitely be a more reliable source of food. Think of winters, when there's little to gather but you can still hunt a mammoth or some other large prey. This way, you take advantage of the muscle/fat the animal built while eating stuff you can't eat.
So, I could see prehistoric nomads being mostly carnivores for a whole season. Which would also leave enough evidence on their remains.
But I agree that the authors seem to have a bias/motive (entrepreneurial and academic) to overstress the importance of eating meat, perhaps cherry-picking on the available evidence.
Hunting small game is reasonably reliable. Hunting primarily big game, as the study is suggests, is the textbook example of unreliable high risk, high reward strategies we teach undergrads about.
What modern human foragers often do is exploit a huge variety of strategies all at once. They're also highly opportunistic and social mechanisms are used to distribute the successes across a large number of people. For instance, if a bunch of Hadza hunters come across a beehive full of honey, they'll stop hunting and eat it. Such finds end up being a significant source of calories for the Hadza, but the study's argument is that this sort of omnivorousness is a recent innovation.
Most of the human population resides in places that don't have harsh winters or winter at all. I have a hard time believing the carnivore diet was required to sustain life anywhere but the northern hemisphere even during the ice ages, eurocentrist bias here?
Those mammoths suggest the presence of rather substantial amounts of greens, unless they belonged to a rare variety of ketogenic mammoths (an ecosystem consisting of mammoths all the way down?).
And sentences such as "[...] baboons [...] devote almost all their daylight hours to feeding [...] while adult Ache and Hadza men spend only a third of the day in food acquisition, preparation, and feeding"? I probably wouldn't go there…
It's kind of convenient that one of the author appears to be selling an app that has just the right diet for the modern troglodyte: https://nutrita.app/author/raphael-sirtoli/