[glecedric]

I read somewhere that the human intestines are not well fitted to digest protein (as we are omnivorous). They start to "rot" as soon as digestive fluids attack them. So the proteins are correctly absorbed in the first meters. After that, the proteins are just wastes going downward (can't find the source back sr).

That's why carnivorous have short but large intestines: they digest proteins as quickly as possible before they turn useless.

Maybe a key point is to span a large amount of proteins intake across several hours (as bodybuilders do, if I am not mistaken).

[dtech]

I highly doubt that without a reliable source. Proteins don't "rot", they fall apart into amino acids which are absorbed. I have never heard amino acids becoming unusable due to long digestion tracts.

The reason I've always heard about carnivores having shorter digestive tracks is that animal matter is much easier to digest than fiber-and-cellulose-laden plant material. In most organisms (expect humans) digestion takes the most % of energy so shortening the digestive tract if it's not necessary is a no-brainer for evolution.