- The Equus genus, which includes all modern horses, zebras and donkeys, first evolved 4.0 to 4.5 million years ago. That's about twice as old as the oldest Equus common ancestor fossil that's ever been found.
- Horse populations changed a lot with climactic changes over the past 2 million years. "Basically, when it's really cold, it's good to be a horse," one of the lead scientists, Eske Willerslev, said during a press conference recorded in Sweden. "When it's warm, it's pretty bad." Willerslev is a geneticist with the Natural History Museum of Denmark.
- The Przewalski's horse really is a wild species; it hasn't interbred with domestic horse.
- The genes for smelling and the immune system seemed to be especially important for horses' survival over generations.