Is it natural for us to eat meat?

A thought has just occured to me. A lot of meat eaters argue that it is natural for humans to eat meat. That we would have the instinct to go out and hunt our food (or select it from Tesco) regardless of what other food is availabe. I don't know about you, but if I was living in the prehistoric world where I had to fend for myself, I would find it a lot easier to dig up a plant than to hunt and kill an animal. Maybe our predecessors only went to the trouble of chasing down other mammals because their plant supplies had dwindled.