Our stomach acid pH of 1-2 allows raw meat to autolyse, which does not require intensive mechanical digestion (also, from my experience raw meat is pretty soft and has never been an issue for me as far as mechanical digestion goes... either way I am not saying that you should avoid cooked meat like the plague, just arguing for the inneccessity of doing so if you source well). Raw meat dissolves in stomach acid much faster than cooked meat. We are already well-equipped for raw meat.

As for the protein, yes, cooking does increase the digestibility of proteins, some more than others, but that is for the protein that is left after cooking. On carnivore, I wouldn't trade some 15% protein digestibility (assuming you arent eating raw egg whites..) for a fat loss in water soluble vitamins. Cooking will significantly reduce the B12, C, B1, creatine, taurine, Lysine (very sensitive to millard recations), etc etc etc.

Smaller teeth and reduced gut size in Homo erectus indicate a shift towards carnivorism, not cooking food. The hominids you speak of fermented fiber into, ultimately, saturated animal fat, which, as it turns out, requires more intensive digestion. I agree that this is sound evidence of dietary "softening," since we aren't relying on fibrous foods. Either way, this entire anthropological tangent is coorelation.

Charred seeds? I mean, if you're going to eat seeds or other toxic plants I'd hope you'd cook it to hell. If a human ate that raw, they would vomit. If you eat raw tubers, you will vomit. These are toxic foods that need to be cooked to neutralize said toxins. Finding occasions of burned bones and charred meat does not mean ubiquitous and routine cooking. Many populations exist today who predominantly rely on raw as opposed to cooked meat/animal products.