You seem to be trying to convince pre-agricultural hunter gatherers who did not even eat meat all that often and had to work hard for every calorie of food they consumed to put a substantial extra effort into cooking their meat

They didn't have to work hard, and they ate meat more than most humans could eat. I just finished reading the part of Clark's A Farewell to Alms where he covers how hunter-gatherers where far better off than basically any farmer. Going through my notes, I see:

The surprise here is that while there is wild variation across forager and shifting cultivation societies, many of them had food production systems which yielded much larger numbers of calories per hour of labor than English agriculture in 1800, at a time when labor productivity in English agriculture was probably the highest in Europe. In 1800 the total value of output per man-hour in English agriculture was 6.6 pence, which would buy 3,600 kilocalories of flour but only 1,800 kilocalories of fats and 1,300 kilocalories of meat. Assuming English farm output was then half grains, onequarter fats, and one-quarter meat, this implies an output of 2,600 calories per worker-hour on average.32 Since the average person ate 2,300 kilocalories per day (table 3.6), each farm worker fed eleven people, so labor productivity was very high in England. Table 3.13 shows in comparison the energy yields of foraging and shifting cultivation societies per worker-hour. The range in labor productivities is huge, but the minimum average labor productivity, that for the Ache in Paraguay, is 1,985 kilocalories per hour, not much below England in 1800. The median yield per labor hour, 6,042 kilocalories, is more than double English labor productivity....Primitive man ate well compared with one of the richest societies in the world in 1800. Indeed British farm laborers by 1863 had just reached the median consumption of these forager and subsistence societies.

In contrast [to the monotonous English diet] hunter-gatherer and subsistence cultivation diets were widely varied. The diet of the Yanomamo, for example, included monkeys, wild pigs, tapirs, armadillos, anteaters, alligators, jaguar, deer, rodents, a large variety of birds, many types of insects, caterpillars, various fish, larvae, freshwater crabs, snakes, toads, frogs, various palm fruits, palm hearts, hardwood fruits, brazil nuts, tubers, mushrooms, plantains, manioc, maize, bananas, and honey.

It's not that much extra effort, and if I ate more meat at the time I would have discovered the (substantial) effect much sooner. Also, if I'd been taught to cook by a human being instead of teaching myself from cookbooks, I would never have made the faulty assumption about that step being skippable. The insight about browning meat fully is easy to discover, and once discovered is normally transmitted to other cooks as part of their training.

Respectfully, you seem to me to be clinging rather hard to an unevidenced theory.

I couldn't find it, but I would guess when we moved from bronze to iron.