Okay? I wasn’t trying to make any claim in contravention of what you just said.

My points were these:

1. the steppe mammoth specifically (i.e. the one everyone means when they reference humans hunting mammoths to extinction) existed as it did because of the mammoth steppe’s unique biome;

2. megafauna that were endemic to the mammoth steppe are not transplantable to any biome we have today, because they were adapted specifically to those conditions (thus the being-endemic, rather than ranging elsewhere), and we no longer have those conditions. (They might survive, but they would quickly adapt out of the phenotype we recognize. You’d just get another elephant.)

I made no claim about the survivability of megafauna that did range outside of the steppe. Clearly, if they were out there, they were able to be out there; and we do have equivalent biomes to those today.

> 1. the steppe mammoth specifically (i.e. the one everyone means when they reference humans hunting mammoths to extinction)

The steppe mammoth became extinct 200,000 years ago, it likely never encountered homo sapiens. The name is also a bit of a misnomer - they were associated with the steppe but were not confined to them.

When people talk about mammoths hunted to extinction by humans, they are usually referring to the woolly mammoth, which had a much wider range. They've been found from southern Spain to Kentucky. They might also be talking about the Columbian mammoth which resided in lower latitude parts of North America as far south as Costa Rica. Both the woolly and columbian mammoths are descended from the steppe mammoth, and both went extinct at the end of the Pleistocene with pygmy populations surviving on islands into the Holocene. Both survived numerous previous interglacial periods.

The "mammoth steppe" is just a poetic name for a biome common at the time, indeed the most common biome on Earth during the age of the woolly mammoth, it's not actually a term for a region the woolly mammoth was endemic to. It is by definition distinct from currently existing steppe climates, but the differences are mostly academic and does not explain the extinction of the mammoths. Indeed it is believed that the decline of the steppe was likely caused by the extinction of the mammoth (and other large herbivores), as they prevented trees from becoming too large or numerous, and in their absence much of the steppe turned into forest.

I’m not sure the distinction you have between mammoth steppe and northwestern US wood bison habitat.

Wood bison are practically identical to steppe bison so the conditions must be very similar. Elephants aren’t cold adapted running into issues well above freezing (~42f), so anyplace that gets midwestern cold like say Mongolia isn’t going to result in them evolving into something roughly equivalent to elephants.

The wood bison's range included tundra! I.e. they were hardier than the steppe-endemic megafauna that were killed off by the retreat and vanishing of the steppe, being able to survive (though probably not thrive) on the sort of scrub brush that grows at the taiga-tundra perimeter (which in turn is all that grows there, because of the lack of enough sun-warming for much of the year.)

Note that maps that claim to depict the "mammoth steppe", that you might find when searching, mostly aren't; they are actually usually maps depicting the range of the set of megafauna we associate with the steppe. But many of those megafauna have ranges that exceed the extent of the mammoth-steppe biome — i.e. they're not endemic to the steppe. So these depictions exaggerate the size of the steppe.

For example, these maps show areas within the arctic circle as part of the steppe — but they definitely were not part of the steppe biome. They were tundra then, just as they are now.

If you divide "megafauna you could find on the mammoth steppe" into "endemic to the steppe" vs "ranged to other biomes, such as tundra", I'm not sure what the precise ratio of the two groups would be; but AFAIK, the species that vanished along with the steppe (mostly not from human predation!) constituted at least a majority of such megafauna.

Which should be obvious — we'd have a lot more megafauna otherwise!

Also,

> Wood bison are practically identical to steppe bison so the conditions must be very similar.

This is an argument from phenotype, and that really doesn't work.

Species that happen to present identically when put into the same habitat, are just doing (over the course of a generation or two) the epigenetic equivalent of convergent evolution — flipping all the methylation switches to activate similar developmental strategies that they both happen to have evolved at some point in the past, either independently or in some common ancestor. (In the case of the wood and steppe bison, that would be the "it's cold, but there's lots of food; so I should get big, get strong enough to defend myself, grow lots of heavy fur, and minimize surface area per volume" strategy.)

But if you take two such "phenotypically identical" species out of the same habitat, and place them into a different habitat, they may have wildly different responses to that adaptive pressure. One species may not have the adaptations the other does, and so one species may do well while the other fails to thrive. Or the two species may have very different adaptations, such that they end up inhabiting different ecological niches in their new habitat, when previously they fit into the same slot.

Which is to say: steppe bison died out (long before the sort of en masse human predation that drove the plains bison to extinction), but wood bison survived. There's probably some good reason for that. (I'm not a zoologist, but I would hazard a guess that it has something to do with the wood bison also being known as the mountain bison — i.e. with their ability to range beyond flat plains/steppe!)

> Species that happen to present identically when put into the same habitat,

Your argument suggested that these are very different environments. “You’d just get another elephant.”

If convergent evolution is pushing the same adaptations then that suggests something already evolved to exist in a similar environment would be reasonably stable especially across human timescales. Kansas gets cold but it’s hardly the Arctic Tundra.