The catch is you have to be smart to take advantage of these things.
On a more serious note, it may be due to similar genetics to humans, specifically the LINE family of transposons.[0] Though, maybe they’re just aliens.[1]
[0] - https://www.livescience.com/jumping-genes-octopus-intelligen...
[1] - https://cordis.europa.eu/article/id/123479-trending-science-...
But we can't actually run down a horse. Only top ultra marathoners can do that.
But walking down a horse? Really?
Horses are incredibly fragile, and over long distances would prefer to be moving at human walking speed.
Horses also require continuous grazing to sustain themselves, and because of how their digestive tracts work, really need time to amass energy.
It's not a question of "running down a horse." It's a question of heat exchange and endurance. Humans are incredibly efficient at maintaining homeostasis "under load." Horses are not.
If you read a histories any war/conflict where there are large numbers of horses involved, a common theme is them just dropping dead of exhaustion along the side of the trail, because they can't sustain the pace of the army marching with them.
This is assuming that most of the army were full of people walking and the horses walking along side were getting exhausted? So an average human can walk down a horse?
Since elephants aren't carnivores I don't think they would get much benefit out of the reasoning skills that enabled us to be really excellent pack hunters, which was probably why more intelligent ancestors of humans managed to out-compete the less intelligent ones.
If elephants gain abstract reasoning skills what does it get them? More efficient harvesting of bananas?
Like maybe if the Wilson Island Mammoths [1] had just a bit easier time of it, or their populations weren't quite as small (or by luck of the dice were much smarter!) then they could have survived.
In fact it would have really helped elephants if some of them were smart enough not to be made extinct by humans! Maybe if humans had been just a little less competent, pressuring but not exterminating the wooly mammoths...
E.g.: humans could reach high technology relatively easily because our environment and physiology enables tool use, etc…
But if “takeoff” is blocked, and evolution continues, then it might still be possible for an aquatic species to overcome the limitations of their environment — but only once they’ve reached the much higher level of intelligence required to find workarounds for their miriad problems!
There would be living ships, of course. This is a Star Maker reference.
It would be fun to imagine a world where the Americas were just out of reach of human migration, but an elephant species on the continents developed speech and abstraction. In my mind it would be a smaller species of elephant, of which there were many, and who may have more need to take advantage of intelligence to prosper.
I also think about r- and K-selected species [1]; whether the survival of a species depends on the fitness of the individual or the fitness of the parent. Humans are incredible parents (being K-selected), and we preserve our line by preserving our children. We're physically decent I suppose, but definitely not as children. Whales are similar, with small numbers of children who require almost heroic parental effort to raise. Elephants are definitely on the same spectrum.
[1] https://www2.nau.edu/lrm22/lessons/r_and_k_selection/r_and_k...