Never said we were actually herbivores. Said we were more like herbivores who supplemented their diet with animal protein than a carnivore. And what Harari said he sourced with biologists' research. I'm in work now, so I can't actually access the book, but listen - while I'm not saying we're some sort of ruminant, I am saying we can easily survive (and thrive) on a plant-based diet (our hunter-gatherer ancestors had to for periods of time). We can not survive our lifetime eating just meat unless we are people like the Inuit ,who eat all the internal organs too, and their whole lifestyle is dedicated to that. But they are not typical at all of humankind.
I'm neither a vegetarian nor vegan, btw. I was a pescatarian from my late teenage years to my early 30's when I used to do cross-country running. But I love chicken and bacon, tbh. And liver and onion too. And Greggs pies. Which is why I'm a fat bastard now, I suppose.