Unlike in Mongolia, where there were large numbers of wild horses available for capture, it seems that most Native Americans on the Plains were reliant on trade or horse-raiding (that is, stealing horses from their neighbors) to maintain good horse stocks initially. In the southern plains (particularly areas under the Comanches and Kiowas), the warm year-round temperature and relatively infrequent snowfall allowed those tribes to eventually raise large herds of their own horses for hunting and as a trade good. While Mongolian horses know to dig in the snow to get the grass underneath, western horses generally do not do this, meaning that they have to be stall-fed in the winter. Consequently in the northern plains, horses remained a valuable trade good and a frequently object of warfare. In both cases, horses were too valuable to be casually eating all of the time and instead Isenberg notes that guarding horses carefully against theft and raiding was one of the key and most time-demanding tasks of life for those tribes which had them.

So to be clear, the Great Plains Native Americans are not living off of their horses, they are using their horses to live off of the bison. The subsistence system isn’t horse based, but bison-based.

At the same time, as Isenberg (op. cit. 70ff) makes clear that this pure-hunting nomadism still existed in a narrow edge of subsistence. From his description, it is hard not to conclude that the margin or survival was quite a bit narrower than the Eurasian Steppe subsistence system and it is also clear that group-size and population density were quite a bit lower. It’s also not clear that this system was fully sustainable in the long run; Pekka Hämäläinen argues in The Comanche Empire (2008) that Comanche bison hunting was potentially already unsustainable in the very long term by the 1830s. It worked well enough in wet years, but an extended drought (which the Plains are subjected to every so often) could cause catastrophic decline in bison numbers, as seems to have happened the 1840s and 1850s. A sequence of such events might have created a receding wave phenomenon among bison numbers – recovering after each dry spell, but a little less each time. Isenberg (op. cit., 83ff) also hints at this, pointing out that once one factors for things like natural predators, illness and so on, estimates of Native American bison hunting look to come dangerously close to tipping over sustainability, although Isenberg does not offer an opinion as to if they did tip over that line. Remember: complete reliance on bison hunting was new, not a centuries tested form of subsistence – if there was an equilibrium to be reached, it had not yet been reached.

In any event, the arrival of commercial bison hunting along with increasing markets for bison goods drove the entire system into a tailspin much faster than the Plains population would have alone. Bison numbers begin to collapse in the 1860s, wrecking the entire system about a century and a half after it had started. I find myself wondering if, given a longer time frame to experiment and adapt the new horses to the Great Plains if Native American society on the plains would have increasingly resembled the pastoral societies of the Eurasian Steppe, perhaps even domesticating and herding bison (as is now sometimes done!) or other animals. In any event, the westward expansion of the United States did not leave time for that system to emerge.

Consequently, the Native Americans of the plains make a bad match for the Dothraki in a lot of ways. They don’t maintain population density of the necessary scale. Isenberg (op. cit., 59) presents a chart of this, to assess the impact of the 1780s smallpox epidemics, noting that even before the epidemic, most of the Plains Native American groups numbered in the single-digit thousands, with just a couple over 10,000 individuals. The largest, the Sioux at 20,000, far less than what we see on the Eurasian Steppe and also less than the 40,000 warriors – and presumably c. 120-150,000 individuals that implies – that Khal Drogo alone supposedly has [in Game of Thrones]. They haven’t had access to the horse for nearly as long or have access to the vast supply of them or live in a part of the world where there are simply large herds of wild horses available. They haven’t had long-term direct trade access to major settled cities and their market goods (which expresses itself particularly in relatively low access to metal products). It is also clear that the Dothraki Sea lacks large herds of animals for the Dothraki to hunt as the Native Americans could hunt bison; there are the rare large predators like the hrakkar, but that is it. Mostly importantly, the Plains Native American subsistence system was still sharply in flux and may not have been sustainable in the long term, whereas the Dothraki have been living as they do, apparently for many centuries.

Bret Devereaux, “That Dothraki Horde, Part II: Subsistence on the Hoof”, A Collection of Unmitigated Pedantry, 2020-12-11.