I think you've taken my cynical description as some mathematical claim which it isn't.
> Why should an unsatisifability instilled in us by evolution be reckoned as more ethically valuable than our actual well-being?
It shouldn't, but it still means that people might do potentially bad things even if everyone's physical well being is ensured, because contentment trumps ethics. I'm not saying it's right jus that it is.
> What evidence shows the unsatisfiability is even there?
The only specific study that I remember off-the-cuff is the one mentioned here [1] (search for "Mike Norton"), but, of course, I think this "unsatisfiabilty" is what brought us here to begin with. Without it, we'd still all be hunters-gatherers. Some of it probably has to do something with social comparison[2]
EDIT:
This is a published study: http://jeffreypfeffer.com/wp-content/uploads/2011/10/DeVoeMo... (overview here: http://www.upworthy.com/why-do-rich-people-seem-to-always-ne...)
> Long-term studies have showed that many people live contented lives for what appear to be understandable psychological reasons.
The problem with that is that much of that contentment appears to stem from the fact that others have less [2],[3]
> Provided it is, why could you not find or produce genuinely engaging challenges
Perhaps. But it is also possible that we have destructive urges that require satisfaction. Freud spends half of his Civilization and its Discontents exploring the "death urge". It isn't science -- far from it -- but it's pretty compelling.
> argument that simply solving one human problem will not immediately bring about utopia ...
I wasn't discussing a specific utopia (even though I personally dream of both a communist utopia and an anarchist utopia), but my thought experiment is meant to doubt that any kind of utopia is possible for a significant period of time. Imagine not how to get there, but what there looks like, and then, think for a while on whether people will really be happy for long in your utopia. That is not to say that we shouldn't strive to build our utopia -- in fact, the impossibility of achieving it is what ensures we'll always have something to do.
> claiming ... that human happiness is categorically impossible
Again, my "approximation" wasn't a well specified law of nature. People are happy with their achievements for a while -- until they're not. In fact, most people are happy some of the time, and some people are happy most the time, but I don't think all people can be happy all -- or even most -- of the time. It's quite possible that people's happiness depends on others' misery. I don't think happiness is impossible; I think utopia is.
[1]: http://www.newrepublic.com/article/120092/billionaires-book-...
[2]: http://en.wikipedia.org/wiki/Social_comparison_theory
[3]: http://www.nytimes.com/2011/07/02/your-money/02shortcuts.htm...