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As you see my other question What would be the major changes to our body if we were herbivores?. Instead of being herbivores, what would happen if we were obligate carnivores?

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Unmodified humans can survive on a animal-only diet (see: Inuit diet). Turning humans into obligate carnivores would require removing the digestive enzymes for dealing with plants, but would not require any changes to the large-scale anatomy.

Humans who evolved from an obligate-carnivore ancestry would likely have differently-shaped teeth, with the incisors better adapted for dealing with meat, but this would not be the case with humans who recently lost the ability to digest plant matter (the advantage of more efficient teeth is only a minor one, and does not provide a strong evolutionary pressure).

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  • $\begingroup$ ...particularly if we assume the humans are still cooking their meat, human teeth are just fine for dealing with cooked meat (and great for meat preserved as jerky). $\endgroup$ – T.E.D. Mar 18 '16 at 15:05
  • $\begingroup$ The article you link says that the diet of the inuit includes plants. $\endgroup$ – gburton Mar 19 '16 at 10:22
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If humans had evolved to be obligate carnivores, then there would be some differences in dentition and digestive system, as well as possibly in our hands and feet.

Teeth:

A carnivore's dentition is, put simply, sharper. Incisors tend to be pointier, there are typically long, pointed canines (rather than the small, typically blunted set humans have), and instead of molars, there are carnassials, teeth designed to cut flesh like a pair of scissors. A carnivore does not need to grind their food, as meat is easily digested even if it is swallowed in relatively large lumps. Their dentition is designed to separate meat from bone and to reduce it to a size that can be swallowed as rapidly as possible.

Guts:

An obligate carnivore has a large stomach that is used to store as much meat as possible, making a meal last as long as possible. The effort needed to digest meat is relatively low, and carnivores have shorter intestines than omnivores.

An obligate-carnivore human's belly might not look too much different to that of a normal human, perhaps flatter when hungry, and more bulging after a meal. They may eat only once each few days rather than several times each day.

Hands and feet:

Carnivores tend to have claws to facilitate the capture of prey. An obligate carnivore human may have claws rather than nails on their fingers and toes to facilitate capture of prey. Such a beings limbs would likely also be more heavily muscled, as they may be required to hang on to struggling prey animals - the disadvantage with carnivory is that the meal can fight back. This may also mean that the skin would need to be tougher.

Some carnivores have very strong jaws to facilitate cracking bones to extract marrow, however for tool-using humans, this can be achieved with the expedient of being able to grip bones and smash them against a hard surface, or by pounding on them with rocks. Hence, such human-like carnivores would make good scavengers too.

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  • $\begingroup$ Humans practice persistence hunting, which doesn't require subduing the prey, but rather chasing it to exhaustion. When your prey has just dropped dead of overheating, you don't need claws or strong muscles. $\endgroup$ – Mark Nov 30 '14 at 22:34
  • $\begingroup$ @Mark, Agreed, but I am positing what would happen if humans had evolved as more active obligate carnivores. Also, persistence hunters still typically finish off their prey when the prey is sufficiently exhausted as to be unable to flee further. $\endgroup$ – Monty Wild Nov 30 '14 at 22:37
  • $\begingroup$ Just to add on to the answer, one thing not to overlook is that we are tool users. Do not underestimate just how much our evolution has been affected by the simple fact that we know how to use sharp rocks and bones to strip meat from bones and fire to cook raw meat into something easier to digest. $\endgroup$ – Brian_Drozd Nov 30 '14 at 22:44
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    $\begingroup$ @Brian_Drozd, I am positing that intelligence evolved after the obligate carnivory. Intelligence and ability to use tools would mean that the hyena niche could be added without requiring exceptionally powerful jaws. $\endgroup$ – Monty Wild Nov 30 '14 at 22:48
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    $\begingroup$ The intestinal tract of a carnivore is shorter than that of a herbivore, so the gut would not need to be as large as a humans or a cow. $\endgroup$ – Oldcat Dec 5 '14 at 22:14

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