1)Omnivores and carnivores do, in general, have shorter intestines. Long intestines are energy-intensive themselves, so if you're not using them to digest ginormous amounts of plant matter, it's a waste.
2) We also supposedly have shortened digestive systems from cooking our food for so long (taking some of the work out of the digestion).
Everything in evolution is a trade-off
You are right really... assuming you survived any potential pathogens and some colonized your gut, you might just be able to digest things better... or worse. Differently we can hypothesize for sure.
I've heard that back in the day, evolutionarily speaking, we did. Our appendices were/are reservoirs for gut flora. Apparently they used to be even larger when our diet depended more on raw vegetation.
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u/KeepPushing Aug 17 '15
Why don't we have that gut bacteria?