These questions are not being posed to offend anyones nutritional needs or macronutrient requirements.
All plants have a season/time of year when they can be eaten, this season is even shorter outside the range of the equator- so how would Pleistocene man have a decent supply of glucose 9-11 months out of the year? Even when in season, hiking in the Northeast of the U.S. I'm surrounded by berries, some veg, and tons of meat/animals. But i could probably dig for weeks without finding a single tuber that contained a decent amount of starch. Plus I've read that a hard frost of 24 degrees or lower will end the season for a potato.
I'm not saying starch isn't a great fuel, because it is and I run better on it, but every time I'm in the wild and then go eat dinner, I say to myself "Theres no starch out there to survive/thrive on. European HGs left Africa way before agriculture and its storage of winter grains, into a seasonal, often cold environment,why am I eating this starch/potato and why does my body perform so much better with it? Hell pemmican is pretty starch free!"
We gorged on fructose, available tubers and maybe late fall vegetables (squash and pumpkins,etc…) which gave us some great pounds for winter survival but theres not much fructose or starch till later in the next year ( i doubt we were getting substantial glycogen from gorging on the spring onions in March)
So did man thrive in a cave/forest eating fatty meat and run on gluconeogenesis for fuel 9-11 months out of the year?-maybe. Did people trek with potato sacks on their backs or have 1000s of pounds of potatoes stored in our caves/tipis- probably not, at least not for more than maybe a few weeks. Did we only perform glycogen depleting activities during the months where we could obtain a decent level of starch? (9 months out of the year-no sprinting, no heavy lifting more than once in a blue moon or significant hoarse playing?-doubt it .Did we huddle and hibernate (humans can't really) for most of the year till starch was available and only then start taking down animals, running around, and digging -probably not.
Lastly, maybe we slept and rested so much when not active (12 hours of sleep and extremely low glycogen depleting exercise volume) that nucleogenisis was less stressful and really was the primary fuel for us? How would that be possible when matched with significant physical activity? -(some have compared the hunting, gathering, animal butchering.etc… life our paleo ancestors to that of a modern day construction worker) Many modern HGs have a rest day or two after a very strenuous day and many of these groups have access to a decent amount of starch. What were we doing in the absence of starch? Were our bones frail from ketosis? Did we have tons of issues like, hair loss,etc… from VLC?- probably not
Our very very close cousins, Neanderthals were mostly carnivorous and were insanely strong/active. Did they eat mostly raw meat (possibly making gluconeogenisis easier?) The real question-How did we survive most of our months and thrive without starch?