Guinea pigs are manmade creatures, they're bred from South American cavies. I saw someone once frame this exact thought as "Lions aren't brave, they're giant predators with powerful muscles, sharp claws and fierce teeth. Guinea pigs are brave, a guinea pig is a 2 pound meat potato with no offensive capabilities that will scream at a human if his lettuce is too wilty."

And a "meat potato" is almost precisely what they are, they're initially raised for food.