Gorillas, like cows, have a digestive system that allows them to synthesize saturated fat from plant material. I wouldn't challenge their diet because they are naturally eating what gives them size, strength and optimum health.

If you tried to eat what a gorilla or cow eats, you would wither away, because you can't make that conversion.

Humans, like dogs, need to eat animal fat for optimum health. Dogs fill the same ecological niche as humans. Once we started hunting together, it was a pretty deadly combo.

That's symbiosis (opposite of parasitism) where two species working together benefit each other.

Except under certain conditions. It is illegal in most US states to hunt with dogs. Because it is just too effective.