Are animals evidenced as having human characteristics?
Assuming consciousness is needed to perceive pain, is there any evidence that agriculturally raised animals can feel pain.
Or, to ask it another way:
Do you think chickens have consciousnesses?
Given that the evidence for this is about as compelling to many people as that for plants... the metaphor seems apt.
Well, are you playing devil's advocate? Do *you* think animals feel as little or as much pain as plants? Also, what is the evidence or lack thereof you're talking about?
Like I said, the problem with consciousness is that you cannot prove anything (well in principle you cannot prove *anything* anyway - like that anything exists apart from you - , but consciousness has something tricky about it on top of that). For example, I cannot be sure that any human around me has a consciousness. Of course, pragmatically speaking, I can be pretty sure.
Now, on that pragmatic level, saying that I'm 100% sure that other humans feel pain (here implying consciously), then I would say you can be sure 99 % or more that other mammals feel pain. Why? Because they are evolutionary, anatomically and behaviourally very close to us (like I said before btw), and pain perception is likely one of the oldest and most basic perceptions there is.
If that helps and gives some credibility to my arguments (of course I could be making this up), I'm doing a neuroscience related PhD, and thus know a little bit about this stuff. And mammalian brains are all very similar. All the basic brain structures are the same, and the differences are mostly quantitative.
It's difficult (ultimately impossible) to say which kind of brain structures create consciousness and which not, but given that those of other mammals are essentially the same as those of humans, and that mammals are so similar in behaviour, I would say that if you want to argue that they do not have consciousness, the burden of "proof" lies on your side.
With chickens/birds it already gets more complicated. If I remember correctly, they do not have a neocortex, which I suppose is mostly indicated to be at least correlated to consciousness. That of course does not mean they do not have it, and there are some structures which are thought to fulfil similar roles as the mammalian neocortex. Taking into account the complex and intelligent behaviour of birds, I think there it is plausible that they have consciousness.
But even in case of doubt, you might as well play it safe and eat plants instead of birds, too....
As far as my real opinion on the matter, I'm an omnivore. If I go fishing and catch fish, I eat them. I don't make them feel unnecessary pain during the process - I always kill them quickly by penetrating the brain with my filet knife, they die pretty much instantly - but I don't feel that there is anything wrong with killing and eating them. I'm fine with eating animals - it's just natural for animals to eat other animals, it's the way the ecosystem works. If we didn't have predators eating prey, the prey animal populations would balloon out of proportion and eat up the food supply until they starve.
I'd just like to point out that
being natural does not imply being ethical . After all, murder and rape are surely natural, too.
Also, we're not talking about the natural balance of the ecosystem here. We're talking about literally billions of farm animals that simply would not exist if we stopped eating meat.
As for the rest of your post, I think I agree with your direction. You say
* you don't think killing for food is inherently wrong.
* you think animals shouldn't suffer unnecessarily.
* there are humane ways to kill animals.
Now, simply based on these points some people would conclude it would be justified to become vegetarians, saying that the amount of suffering involved with farming is simply and plainly unnecessary, seeing as there is an alternative to eating meat (plants), and eating meat is merely a luxury (btw, even if you think eating meat is necessary for health reasons, it surely would be in much lower quantities than it happens today).
And even if you don't oppose killing animals and there exist humane ways to rise and kill them, the question is what methods are *actually* used, and you should base your decision on that. To give an analogue, I think it is justified to boycott "blood" diamonds, and that is not changed by the fact that the mining of diamonds is not in principle unethical, nor that there exist ethically mined diamonds (i.e. if you only boycott the blood diamonds).
Btw, I'm not trying to convince you here to become a vegetarian, but rather that the reasoning behind becoming one can be sound.