Przewalksi’s horse is genetically distinct from modern horses (it has an extra chromosome pair). It went extinct in the wild in 1969, but a small population was introduced to the Chernobyl Exclusion Zone in 1998; they have thrived.
Przewalski’s horse is a genetic curiosity. It has one more chromosome pair than all domesticated horses, for starters. Some taxonomists classify Przewalski’s horse as a separate species, even though it can effectively interbreed with domestic horses. It diverged genetically from other horses thousands of years ago. Estimates of just how long ago vary, from 38,000 to 160,000 years ago, but this certainly comes well before the domestication of the horse.
(Side note: the first culture to domesticate horses was the Botai, about five thousand years ago. They lived in an area that is today part of Kazakhstan. The horses the Botai domesticated were probably Przewalski’s horses, although today’s Przewalski’s horses – and modern horses – are not descended from that Botai horse population.)
Przewalski’s horses ran wild in the Gobi Desert for a few thousand years before finally going extinct in the wild in 1969. Fortunately zoos and wildlife parks have maintained a captive population. For the last thirty years they’ve been reintroducing the horse to the wild. And that “wild” includes at least one rather unorthodox location: Chernobyl.
I’ve written before about involuntary parks, areas that are human-free for political or safety reasons. In the absence of human settlement, nature returns and thrives. The thirty kilometres around the Chernobyl nuclear power plant in Ukraine is an involuntary park; the area is highly radioactive, but is now covered in trees and swimming with deer, moose, badgers, boars, and wolves. And, since 1998, it also hosts a small population of Przewalski’s horses.
From the original group of 31 horses introduced to Chernobyl, more than a hundred are thought to be roaming through the exclusion zone. The effects of Chernobyl’s radiation on the local animals is not positive (mutations are common), but apparently it’s much less negative than the presence of humankind.