Funny coincidence: I was watching tv late last night (well, actually listening to it in the background while sewing on my 'mid shelter) and it was a show about what kind of life foms aliens would be potentially like, so they took a quick look at life forms on earth... First, they looked at grass and how it gets its engery- from the sun. Fine and dandy, but ti doesn't produce that much energy so it isn't able to do much. Which is why vegetables are, uh, "vegetables". Next they looked at a sheep that was eating the grass. It gets more energy from the grass than so it's able to do stuff like run, jump, etc. They showed on a plate how much grass (I think- was actually sewing) it needs to eat to power its brain for a day (or whole body? sorry). Then they showed in comparison how much grass it would take to power our brain- and it was a lot. Like a giant burlap sac's worth. The point was if all we ate was grass, we wouldn't have time to do much else besides eat. Or - we could just eat some meat, at which point they brought out a leg of lamb for the guy in the demonstration to eat. Which I that was in poor taste (pun) to eat a leg of lamb right in front of another lamb...kind of cold hearted. So their conclusion was that alines with enough intelligence to travel across space to get here would most likely be carnivorous and might look at us and our planet as another food source (paraphrasing).
But a few years ago I watched another discovery channel show where the scientists were arguing that our early monkey ancestor's (if you believe in evolution) rapid brain development that put them ahead of the other monkeys was because they ate red meat, and the rest stayed herbivores. Apparently the nutrition in red meat gave their brains a developmental kick start. So, according to them we'd still swinging from the trees if we didn't eat meat.
And that leads into an anecdotal story which is an issue I've heard can happen to vegetarians- and that's memory loss. I had a co-worker who, him and his girlfriend, were vegetarians. They ended up going to their doctor because of memory problems and their doctor's prescription was to eat some red meat.
Anyway- I just thought it was funny to see that show the same day after stumbling across this thread, and how it ties into other things I've run across regarding brain development and meat eating.