We often wonder how people of the past, including the most revered and refined, could have universally engaged in conduct now considered unconscionable. Such as slavery. How could the Founders, so sublimely devoted to human liberty, have lived with — some participating in — human slavery? Or fourscore years later, how could the saintly Lincoln, an implacable opponent of slavery, have nevertheless spoken of and believed in African inferiority?

While retrospective judgment tends to make us feel superior to our ancestors, it should really evoke humility. Surely some contemporary practices will be deemed equally abominable by succeeding generations. The only question is: Which ones?

I’ve long thought it will be our treatment of animals. I’m convinced that our great-grandchildren will find it difficult to believe that we actually raised, herded and slaughtered them on an industrial scale — for the eating.

To be sure, there has been a salutary turn in our attitude toward animals, especially their display and confinement. To its credit, Barnum & Bailey is retiring its elephant acts. Festooning these magnificent creatures with comically gaudy costumes and parading them about, often shackled, is a reproach to both their nobility and our humanity.

Or consider those SeaWorld commercials reassuring us how well their orcas are treated. The tone is contrite and almost apologetic, as befits a business that trains splendid creatures to jump high on command for fish — and for our amusement.

And although some of these measures are market-driven — SeaWorld has been hemorrhaging customers and Cirque du Soleil has been thriving without animals — they are nonetheless welcome. As are the improvements in zoos. The zoo animals I remember from my childhood were so sadly caged, so restlessly pawing the ground, so piteously defeated. Today, the enclosures are more forgiving, the bars largely gone, the running space more ample.

It’s understandable. The zoo used to symbolize man’s dominion over his menacing adversaries, his competitors for living space. Tigers still roamed, and could eat you. Now the competition is over. Our rivals have either been wiped out or driven back to the bush. Except for the occasional shark dining on some intrepid surfer, the threat is gone — and with it, the thrill of conquest.

No need, therefore, to display wildlife bound and tamed, King Kong-like. The overriding mission of today’s zoo is conservancy — the care, study, preservation and propagation of the various species, some of them endangered.

Another advance, and not just for them but for us. One measure of human moral progress — amid and despite the savageries we visit upon each other — is how we treat the innocent in our care. And none are more innocent than these.

Which brings us to meat-eating. Its extinction will, I believe, ultimately come. And be largely market-driven, as well. Science will find dietary substitutes that can be produced at infinitely less cost and effort. At which point, meat will become a kind of exotic indulgence, what the cigar (of “Cigar Aficionado”) is to the dying tobacco culture of today.

As a moderate carnivore myself, I confess to living in Jeffersonian hypocrisy. It’s a bit late for me to live on berries and veggies. My concession to my qualms is a few idiosyncratic distinctions (of no particular import). And while I don’t demand that every chicken I consume be certified to have enjoyed an open meadow and a vibrant social life, if I can eat free range, I will.

No. I’m not joining PETA. Indeed, I firmly believe that man is the measure of all things. Sometimes you have to choose. I cringe at medical experimentation, but if you need to study cats’ eyes in order to spare some humans from blindness, do it. (Though not to test cosmetics.)

If the Delta smelt has to die to conserve 1.4 trillion gallons of water for the parched humans of California, so be it. If the mating habits of the Arctic caribou have to be disturbed so we can produce 1 million barrels of oil a day — on a drilling footprint the size of Dulles Airport in a refuge the size of Ireland — I say: Apologize to the amorous herd, then drill.

But some things are unnecessary. Caging beautiful creatures. Displaying them for spectacle. It’s good that these are being rethought.

The cheeseburger question we leave to our progeny. Though, when their time comes, they should refrain from moral preening. They will, by then, have invented abominations of their very own. Humans always do.

© 2015, The Washington Post Writers Group