Decoupling happiness from state of the world: Useful? Against human nature?

This is a very well known sentiment in Buddhist circles. The canonical metaphor for this is "leather shoes" -- you can't cover all earth in leather but you can cover your feet.

There are certainly two paths, and you're right that the path of least resistance in following our greed for ease and comfort has brought us to all these great inventions. The question is, are we psychologically more satisfied than we were in old times? The quality of life has improved without doubt, but do we feel better? (and do we feel better specifically due to that, or could there be something else going on hand in hand)

It would be a truism to say that lovers are happy in hovel and that the rich also cry. These days people in affected ethnic neighborhoods probably enjoy higher basic living standards than the elite in medieval times. Do they feel happier?

In Buddhism, happiness/suffering depends on a match between "is" and "should", or your perception of the situation on one hand and your expectations on the other. If the two mismatch, one will feel unhappy no matter how good the situation is, objectively. In other words, Buddhism defines happiness as a mental/emotional state conditional on one's values ("attachments").

So the Buddhist way of making "the leather shoes" for the mind, is to learn to transcend any fixed idea of the world, as well as any fixed set of expectations, and learn to dive into the spontaneity of life as is, with infinite openness and no sense of conflict. This is subjectively experienced as acceptance (aka love) of oneself and the world, or the perfect ease and spontaneity. This stateless state of having no ego, no fixed position, and therefore no suffering, is what we call Nirvana, and the Christians call unity with God.

Is it desirable to have entire population of Earth to get into this state of spontaneous freedom and what would happen to society and the very civilization? Until I experienced it first-hand I used to think that civilization would die out from the lack of activity. Now I have all reasons to believe that once the mind lets go of its conceptual boundaries, it gets to see that the nature of reality is not as fixed as we used to believe. So, in my opinion, when we are all free, instead of dying out the civilization will enter a phase of increased playfulness and creativity. Instead of being victims in our collective nightmares, we will be dreaming our own dreams, collectively and individually. I want to be around when that happens.

A canonical explanation for why Buddhism is necessary or desirable is told in the story of the four messengers (see here or here).

My paraphrase of the story is that Siddhārtha Gautama was born a prince; it was prophesied that he'd become a Buddha or a World-Ruler; his father preferred the latter and so tried to keep the existence of "suffering" a secret frm the young prince, who lived secluded in a luxurious palace. Eventually the prince went outside and discovered that the world includes sickness, old age, and death; and, either poverty, or the life of a monk (or both, depending on how the story is told).

Anyway on discovering this the prince was something like, "how can I be happy when everything is impermanent, everyone is going to die, etc.?"

So he set off (literally, i.e. he left the palace and his family) to discover the antidote to (the escape or liberation from) suffering and so on; and eventually discovered enlightenment or became enlightened, including how to teach that, and for the rest of his life he taught people Buddhism so that they could be liberated too.

Anyway, Buddhism as taught in the Pali canon includes doctrine that you cannot expect permanently satisfying feelings from sensual perceptions, therefore it's unwise or ignoble to seek sensual pleasure, that it's better to have Right View and so on, and pursue the Threefold Training.

Maybe Buddhism would say that this is not against human nature but is against animal nature: i.e. pursuing wisdom and morality and concentration is something that a human can and should do, that an animal typically can't and doesn't; and that a human who doesn't is not unlike an animal.

Also I think the "hedonic treadmill" you mentioned might be more-or-less analogous to "samsara".

Also I think that Buddhism expects that there will be lay people (lay society) and monks. Everyone needs various basic "necessities": especially food and medicine, maybe clothing and shelter -- not to mention intangible and social goods like education etc. Lay people are expected to engage in some form of livelihood, to everyone's benefit (their own, their family's, their teachers', their employees and employers). One of the Buddhist ideals is a "Middle Way" between sheer hedonism and consumerism on the one hand, and asceticism and starvation and so on on the other.

Chris’s answer maybe alludes to this, but I want to highlight why the question you are asking is tangential to the teaching of the Buddha.

The primary aim of the Buddha’s teaching is not inventions, technological progress, comforts, certain social structures one might consider preferable etc. It is the end of suffering, a goal that, he taught is independent of these things.

Second, whether something is natural is not relevant. What is relevant is whether it contributes to an increase or decrease of suffering. Something being natural doesn’t even mean it’s good. All our defilements are natural. In fact, it is taught by the Buddha to view these arisings as mere nature (not to impute “my” onto them). Much of our animal nature points us to acts that would not be considered wholesome by the wise. The Teaching encourages us to understand nature as it is and act wisely in accordance with that understanding, not to act out whatever urge naturally pops up in our mind. Whether to phrase it as animal nature vs. human nature or as the animal nature of humans is a matter of choosing words.

This point was beautifully summarized in a little booklet by Lama Yeshe I read years ago. I can’t recall its title now, but there was a small section in it that was titled “Don’t be yourself” and that was the message of the section, that you can do better than that.

Please note that nature and evolution optimized us for survival and procreation. They did not endow us with tools to not suffer. The latter is the territory of the Teaching and is the reason why a Buddha had to arise and teach us. In fact, much of our stress is from primal reactions bestowed on us by nature for the two goals it cares about. The Teaching actually doesn’t care to understand origins and evolution and how we got to be endowed with all the urges and reactions we naturally have. Just to understand that they are present, know them exactly as they are and skillfully use this knowledge to relieve the suffering.