The Botai culture (3700 – 3100 BCE), in present-day Kazakhstan, represents an uncommon mode of subsistence: equestrian hunting. The fact that the Botai folk have domesticated horses makes them different from most hunters and gatherers, while the fact that they depend heavily on hunting makes them different from later herders in the region.
The most famous equestrian hunters are the American Plains Indians of the seventeenth to nineteenth centuries. These were a varied assortment of tribes, with origins among more settled Indian groups, who took up riding after Spaniards reintroduced the horse (which had gone extinct in North America, along with other megafauna, twelve thousand years earlier). Plains Indians depended on hunting bison for most of their diet. The Botai folk were not hunting bison of course, but wild horses. Horses supplied the overwhelming part of their diet; 90% of animal bones in their settlements come from horses. There was an argument for a while about whether the Botai folk really had domesticated horses. However, this has been settled by the discovery of pottery containing residues of mare’s milk; obviously no one is arguing that they were milking wild horses. So unlike American Indians, Botai folk milked their horses. It is also likely that they were riding horses and using them for traction. There is evidence for bit wear on the teeth of some of their horses, and it’s hard to see how they could have gotten whole wild horse carcasses back home (as they did) without having tame horses to pull the carcasses, probably on sledges.
The fact that the Botai folk had horse milk in their diet, along with lots of horse meat, is interesting. Horse milk is sweet (6.3% lactose vs. 1.3% fat, close to human milk), sweeter than cow’s milk (4.6% lactose vs. 3.4% fat). Any Botai individual who carried the lactase persistence allele, which allows carriers to digest lactose (milk sugar) past infancy and into adulthood, would presumably have had a strong fitness advantage. The ability to digest lactose might have been particularly important for kids making the transition from mother’s milk to horse meat.
Horses and horse riding and horse traction play an enormous role in Eurasian history. They are probably a major factor in the expansion of speakers of Indo-European languages. The Botai folk were almost certainly not the original Proto-Indo-European (PIE) speakers – the PIE vocabulary doesn’t fit – but they or people like them might have played some role in Indo-European origins, even if their language didn’t prevail.