i agree with simple simon about the meat issue it is very costly and wastefull to produce meat for the current population. as far as humans are concerned we are the most highly effective predator this planet has yet seen and we are highhly adaptable killers. we have hunted and ate all known large mammals for thousands of years from elephants to whales the weapons and marks on bones from arrow and spear strikes are evident as far back as recorded history goes we are clever and also scavenge and farm but to say humans are not extreamly effective hunters is a stretch i think. it is believed that a number of the large mammals and some predators were hunted or outcompeted by early humans all the way to extinction in north america like ground sloths/saber tothed tigers etc... you can eat raw meat if you want we have been cooking for thousands of years because things are better that way and easier to consume and digest plants also. we use to eat things raw the appendix once helped with this and we produced stronger digestive enzymes thousands of years ago these traits are slowly going away because they are no longer needed. as an example dogs can bury raw meat and eat it weeks later without problems early humans also had this ability