I did not know that modern humans can not survive on a diet of raw food - but apparently
eating raw plants and meat requires much more energy to digest. Cooking food makes it much easier to digest. Indeed,
just breaking food down into smaller particles makes it easier to digest - so tenderizing meat by pounding it with rocks
means less chewing is involved. (Or pureeing your food in blender would work too, but only if you want to go through life getting
your nourishment from "shakes")
A diet of cooked food means that humans did need to spend as much time eating. This allowed them to range
further from camp, allowing them to hunt longer. If the hunt was unsuccessful, the hunters can return to a meal of gathered
roots, fruits and seeds - because these foods are cooked, the meal can easily and rapidly be consumed in the evening light.
If the gathered plant food was all eaten raw, it would take much longer to chew and digest. Apes spend hours chewing on their leafy diets.
There are a number of studies that show density of the food eaten matters - for example, two sets of rats were fed pellets of food
with exact same caloric value, but one set of rats got dense hard food stuffs while the second set of rats had their pellets granulated for
easy consumption - the second set of rats gained more weight. Chewing and digesting consumes calories.
Because cooked food is softer and easier to chew and digest, humans lost their big teeth and mighty jaw muscles. Apes have bones on
top of their skulls to anchor their chewing muscles, but the human jaw and corresponding muscles, and teeth are all much smaller - next time you see a photograph
of a chimpanzee, look at how big its teeth and jaws are. The human
stomach and intenstines are also much smaller than digestive tracts of primates of corresponding size.
When our early ancestors became meat eaters, they began ingesting high caloric food that allowed them
to grow bigger brains. This explains why gut size decreased, a stomach and intestinal tract of a meat eating human is more like a wolf
than like a gorilla - but this eating meat does not explain why human tooth and jaws shrank, when one would expect the opposite in
a creature that evolved into a meat eater. It is the fact that humans cook their meat, while wolves eat theirs raw, that explains why human teeth and jaw shrank over the generations.
Wild animals prefer cooked food, if they can get it.
Modern humans still prefer to eat soft, easy to digest food. Who wouldn't prefer a chocolate eclair over a salad of raw carrots and kale? Now food is so plentiful that it leads to
rampant obesity and diabetes.
Control of fire also allowed humans to fend off larger predators. Control of fire allowed humans to evolve into
the hairless primate that we are today; with only one significant patch of fur, which is on the top of our head. The hairless human body allows for
more efficient cooling in hot environments, a great benefit to humans who chased after furred prey, who overheated more quickly
in the dry savannah environment. Other animals can't shed fur during hot days because they need to keep warm at night, whereas
control of fire meant humans could survive cold nights without fur.
This fascinating book is only 200 pages long, the rest is footnotes. Short though
it may be, it makes an interesting read.