Biology Reference
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domestic dog cannot keep up in the heat with a fit human athlete. Since they hunted (bone marks
from demeating butchered bones with stone tools, like the long horned Pelorovis buffalo bones
in Olduvai, are overlaid by carnivore tooth marks of lions, hyenas, and wolves suggesting they
did their own hunting and kept at bay other carnivores from their kills) or scavenged food was
high in fat and protein, they cooked it in order to break it down into smaller better absorbable
particles improving digestion and absorption. Cooking made food absorption more efficient.
Furthermore, meat and fat, particularly from bone marrow from scavenged or hunted carcasses
that Homo erectus undoubtedly ate would have had a lot more energy per calorie expended to
find food in comparison to tubers or nuts. Conversely, gorillas have to spend a lot of time
eating to consume enough vegetation to satisfy their protein and calorie needs. Their colons are
80% longer than ours to bacterially ferment fiber and cellulose into fatty acids that are then
absorbed for energy. For every gram of fiber they eat only about 1.5 calories is produced. For
example in comparison to other large apes, we have an intestinal system that is a third smaller
than would be expected. Humans cannot naturally survive on carbohydrates alone and develop
health problems, less fertility and amenorrhea with pure plant food diets. Hunter-gatherers get
a return of 3,500 kjoules (836 calories) to 6,500 kjoules per hour compared to 60,000).
kjoules per hour of effort for killing a large herbivore. While carbohydrates may have
provided about 15-20% of energy, protein could not make up the rest because as humans we
cannot obtain more than about 50% of calories from protein because our livers are not large
enough to handle the protein and amino acid/urea/nitrogen loads of higher protein content diets,
hence the high-protein diets that result in weight loss. To make up the difference we have to
obtain the additional calories demanded by our brains from fat. In other words, we are to some
extent obligatory fat eaters for one quarter to half our energy needs. There is ample evidence
from Africa, Europe, Asia, and the Levant that erectus preferentially hunted primitive
elephants, hippos, rhino, probably because of the higher fat content of elephants, ease of
hunting them along their regular game trails to water by spearing them or cutting their tendons,
or killing them in pits as the Bantu were doing when Harris came across the Bantu hunters in
the Okavango swamps (apart from hunting also weaker tribes). Per gram, carbohydrates yield
about 4 kcal/gram, protein about 4 kcal/gram but fat yields 9 and of note, alcohol yields 7,
hence beer paunches from the combination of alcohol and carbohydrate. In medical school we
had experiments to calculate the calorific content of food - which was not that difficult.
Soaking ground up food in an emulsifier or lipophilic solvent like acetone, xylene, chloroform,
ethanol, benzene, toluene, or ether and measuring the additional weight tells how much fat is
present; protein content can be determined by nitrogen content and carbohydrate content by
burning a sample of the food, weighing the residue and then calculating the carbohydrate
content by subtracting the protein and fat content. However, how much is absorbed in a diet is
dependent on how raw the food is, how big the particles are, and how much it has been
cooked. Thus, for example, in a hamburger with processed flour and minced meat that is well
cooked, absorption is maximal. The calorie counts on food packages do not take into account
these differences in absorption. Be that is it may, the digestive system is designed for maximal
absorption in an efficient small intestine of about 22 feet for all fat, most protein, and
depending on fiber content, carbohydrates to provide the energy for the very high demands of
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