Most mammals "eat" a lot of fat.
For example, a gorilla's diet is 60% fat.
Its voluminous large intestines ferments fibrous plants into short chain fatty acids, and thus a high fat diet.
Compared to the great apes, humans have vastly diminished large intestines. We can't ferment fiber like they can. We traded the metabolically demanding gut for an energy expensive brain.
Since we don't have the endogenous fat-producing-capabilities of great apes, it makes sense to replace this with exogenous fat consumption from animals.
Who would have thought...?
