It seems like we have two disagreements. The first is whether there are living conditions to which death is preferable, and the second is over how bad the conditions wild animals live in are. About the first:
I'm not a negative utilitarian, I don't think suffering should lexically override happiness. I just think the suffering outweighs the happiness here because there is more of it. I definitely don't think humanity should be wiped out too. Humanity wouldn't otherwise be living in conditions worse than nonexistence, and has a good chance of living in better conditions in the future. Humanity is also the only potential manifestation of good in the universe, as far as we know.
If you have a problem with wanting to kill someone to put them out of their misery in general, what if you were going to be tortured forever? Wouldn't you want to die then? If staying alive seems like it should lexically override pain when you look at a single individual, think about all the future individuals who you probably don't think have any special claim to life that comes with already existing, whose suffering you would be preventing by killing the present generation. If the species is expected to continue long enough, barring time-discounting, they should vastly outweigh the cost of killing the current. And no matter how long the species is going to continue, it's going to die some time, so you're really only moving an event forward in time, not introducing it from nowhere.
About the second:
I see no reason to expect that if animals have reduced awareness and other neurological faculties that reduce their ability to suffer, it wouldn't also limit their ability to experience positive things too. Even if with what they're lacking, they suffer only 1/10 as much as humans, the vast numbers of animals in the world seem to outweigh that.
The possibility of a hedonic treadmill in animals is something to keep in mind, but I suspect that it is not as evolutionarily helpful in short lived animals that aren't likely to live for many years after a major negative event. The Wikipedia article said it took weeks in humans for the treadmill to kick in and make it so "positive emotions actually outweighed their negative ones."
There is an obvious evolutionary force that would push animals like humans that can live for decades to mentally recover from terrible circumstances, but there is nothing for all of the animals that are hit by something they have a low chance of surviving. If a gazelle breaks a bone in its leg, it is basically dead, and there is no selective pressure to keep its mind in operable condition.
And most animals don't live the kind of lives that shape the genes of their species. Most animals die before reproducing. I expect that the genes of most animals are tailored to benefit the lucky ones who aren't infected by some parasite, and who can find enough food.
It seems like we have two disagreements. The first is whether there are living conditions to which death is preferable, and the second is over how bad the conditions wild animals live in are.
I agree that there are circumstances to which death is preferable, although I've argued a number of times on this site that people who're making that decision with respect to themselves are usually in a bad position to do so.
I strongly disagree that the conditions on wild animals are that bad.
There's a very strong selective pressure for animals to be adapted to thei...
Assume for the time being that it will forever remain beyond the scope of science to change Human Nature. AGI is also impossible, as is Nanotech, BioImmortality, and those things.
Douglas Adams mice finished their human experiment, giving to you, personally, the job of redesigning earth, and specially human society, according to your wildest utopian dreams, but you can't change the unchangeables above.
You can play with architecture, engineering, gender ratio, clothing, money, science grants, governments, feeding rituals, family constitution, the constitution itself, education, etc... Just don't forget if you slide something too far away from what our evolved brains were designed to accept, things may slide back, or instability and catastrophe may ensue.
Finally, if you are not the kind of utilitarian that assigns exactly the same amount of importance to your desires, and to that of others, I want you to create this Utopia for yourself, and your values, not everyone.
The point of this exercise is: The vast majority of folk not related to this community that I know, when asked about an ideal world, will not change human nature, or animal suffering, or things like that, they'll think about changing whatever the newspaper editors have been writing about last few weeks. I am wondering if there is symmetry here, and folks from this community here do not spend that much time thinking about those kinds of change which don't rely on transformative technologies. It is just an intuition pump, a gedankenexperiment if you will. Force your brain to face this counterfactual reality, and make the best world you can given those constraints. Maybe, if sufficiently many post here, the results might clarify something about CEV, or the sociology of LessWrongers...