thethingthatlurks said:
Uhm, no? Spinach is just an example with which all of us would be familiar. The same is true for other leafy vegetables. Also to the best of my knowledge, spinach hasn't been selectively bred for its iron content, which isn't even available for you unless you know what you are doing. As for lemons, any citrus fruit will do. Or berries. Or root veggies like carrots. Oh, and broccoli. Do you really think lemons are special? Or for that matter artificially selected to provide even more vitamin C? Sorry mate, you're full of crap.
Yes, yes they are. Not for those specific things no, because when they did that they didn't even know vitamins existed. Fact is, humans have picked certain plants and have cultivated them for millenia, selectively breeding them in the proces. Pretty much every vegetable we eat at the moment doesn't exist in nature in that form, they're all cultivated species. Citrus fruits, beans and broccoli are excellent examples of that actually.
But even without that, you're assuming that you can find them in large enough quantities to survive on. You're also assuming you can easily find combinations like spinach and citrus fruits together, and you're assuming you can find them easily enough so that you spend less calories gathering them than you get from them. Why do you think herbivores have huge digestive tracks? It's pretty damn hard getting enough energy from pure plant material.
Humans have never lived on plant material alone, hell, there are strong indications that eating animal products was one of the forces in our evolution [http://berkeley.edu/news/media/releases/99legacy/6-14-1999a.html]. So why on earth do you think you could do something that humans have pretty much never done? You're not a deer.
But let's try something else. How well would you survive? Let's just try a simple test. One of the following will kill you in a horrible way, the other one is quite delicious. Can you guess which one?
Honestly I'd just set traps for rabbits and other small critters. But I'll play your game; they're cuttlefish, the first one is poisoness, the second is edible. The warning colours are a dead giveaway.
But it's not something to be smug about, plants and mushrooms have the same problem.