evidence: Humans have short, soft fingernails and small "canine" teeth. In contrast, carnivores all have sharp claws and large canine teeth that are capable of tearing flesh. Carnivores’ jaws move only up and down, requiring them to tear chunks of flesh from their prey and swallow them whole. Humans and other herbivores can move their jaws up and down and from side to side, allowing them to grind up fruit and vegetables with their back teeth. Like other herbivores’ teeth, humans’ back molars are flat for grinding fibrous plant foods. [...] Carnivorous animals swallow their food whole, relying on extremely acidic stomach juices to break down flesh and kill the dangerous bacteria in it, which would otherwise sicken or kill them. Our stomach acids are much weaker in comparison, because strong acids aren’t needed to digest prechewed fruits and vegetables.