The Yukon horse and the Nevada horse represented the last traces of a North American phenomenon that has perplexed us for generations-the evolution and the loss of recent horse species. The Yukon, Equus lambei resembled Przewalski’s species, Equus ferus przewalskii, while the large Nevada, Equus scotti, is thought to be close to the basic zebra line. This species could even stretch its ancestry to the very early European Equus stenonis, which was also a big species.
While some recent horse species evolved in America, then migrated 11mya to Eurasia and Africa, those remaining in their “native” land area eventually became extinct. The reasons are not hard to imagine. Most of the so-called megafauna died out at the same time, because of climate change in the form of global cooling, grass species change and/or human disruption. Unfortunately, horse meat was very popular on the menu of early humans in Eurasia, at least, and still is. The modern domestic horse, Equus ferus caballus, the domestic donkey (also found in the wild as the ass), the ass’ cousin the onager, the tarpan, kiang and zebras are all we have left, with none in North America, save a few remnants of “ferals” that the ranchers allow from the once-thriving mustangs brought in by the Spanish. Most successful in the wild are the plains zebra, Equus quagga (not the extinct quagga)
Strange discoveries may still remain in the opposite direction from Eurasia, which the equines reached via the link area known as Beringia (after the Bering Strait.) In South America, which was already connected via the Panamanian isthmus, Equus andium and 4 other small species are thought to have survived well from the Middle Pleistocene (1mya) to the early Holocene (700,000ya.) They could not have replaced horse species that lived there before them, as it is likely they crossed over when the isthmus formed, around 3 million years ago.
The reverse of the usual scientific process is happening here. More often than not, we allow information about wild species to illustrate how domestic species have changed. The rich genetic information we have used from 59 horse genomes in
Horses Look Back informs us about how wild species may have evolved.
The graphs and detail in that paper give a real feel of the background science.
What makes horse sense is that the modern horse species’ teeth, longer legs and neck, one-toed hoof and digestion suit the plains of America, Eurasia, Africa and even the pampas, it seems. We can be grateful that magnificent creatures like these still remain on the planet at all. Many are disappearing fast, as we read. They can be saved with real appreciation of what horses mean to humans, not only in our history, but at an iconic, almost religious level.