Casy, as I said, perhaps hunting and eating meat did play a significant role in human evolution. But have a look at this interesting piece:
http://paleovegan.blogspot.com/2010/08/rip-eth.html
Whatever the truth of the matter may be, few people today have to eat meat in order to live and flourish. If we want to reduce the amount of suffering and death we inflict on the rest of the animal world, we can.
As for plants feeling pain:
http://en.wikipedia.org/wiki/Plant_neurobiology
http://www.dowebsites.net/linv/images/about_pdf/Trends%202007%20Alpi.pdf
Those who claim that plants can feel pain are on very shaky ground. But let’s suppose for the sake of argument that plants can indeed feel pain. The question then is, how much pain is there and what kind of plant “self” exists that experiences this pain? We would have to decide who suffers more: a cow or a cabbage. Even on the unlikely assumption that plants can feel pain, I’m pretty sure we would be inflicting less suffering, and less loss of valuable future experiences, on plants than on animals. But if more suffering and loss were caused by eating plants, then I might have to eat meat instead — however yucky that prospect would be.