1/ Cooking was used in an economy of survival since all times. Cooking roots or hard leaves is mandatory but not meat nor fish nor fruits nor other leaves.
2/ It is only in the era of cheap and abundant energy
(one hundred years ago) that our habit of cooking all food and
recooking a substantial amount of them occurred. We cooked to digest non edible stuff like cereals and to increase the amount of calories absorbed by our digestive tract. We also cooked in order
to produce some other factors linked to flavors and Maillard products.
3/ On the other hand modern cooking at high temperatures diminish drastically the content of
non caloric nutrients, oxidised fats and create xenobiotic molecules at a time where we are aging in urban areas and need more micronutrients instead of more calories.
4/ Apart from child mortality the lifespan of hunter gatherer was not ours because of
famine, accidents and severe infections or parasites. Yes some of them
could have died at old ages but they were few because of the uncertainty
of food supply, the dangers of wild life and the absence of efficient
care. So the assumption of a doubling average lifespan in our times is robust. In
this perspective and according to epidemiological studies like those
conducted in Okinawa island it is fact based to warn our population on
the risks of cooking all their food especially at high temperature or directly on fire either because of the destruction of non
caloric nutrients or because of the generation of organic molecules
which have carcinogenic properties.
5/ BTW when I saw paleo eaters
grilling their stuff every day I think they buy paleo but they eat
modern cooked food. The result will not be as they expect it.