For years now, the evolution of the horse to the domesticated animal it is today was thought to be a fairly straightforward path. So straightforward, in fact, that the steps from ancient to modern horse could be a simple t-shirt graphic. But as the 1960s American comedy “Mister Ed’s” theme song puts it, scientists “went right to the source and asked the horse” to find out if that was indeed the case. A 700,000-year-old horse to be exact and what they found shattered everything we believed about the evolution of the farmer’s most beloved work animal.
A fossilized bone of an extinct and ancient horse was found in permafrost near Thistle Creek, Canada in 2003. It was the source of the now oldest complete genome ever to be sequenced. Previously, the record was held by an 80,000-year-old cousin of humans.
Anyway, a multinational team of scientists were able to time-travel back through the evolution of the horse and see exactly how it got here. The trip the horse made forward was anything but simple, straight and sure-footed. The path branched in many directions, sometimes leading to dead-ends, swelled in places where it appeared certain horse-kinds would prevail but some died off nonetheless, and the lineage otherwise pitched and turned until the modern horse was forged.
It now appears that all modern horses, zebras and donkeys came from the same ancestor that pounded across frozen grasslands twice as long ago as we originally thought – about 4 million years ago. But our sequenced DNA horse evolutionary record goes back only 700,000 years – that stretches further back than the evolutionary records we currently have on man or other beasts though.
Along the way the researchers were able to confirm that Przewalski’s horse, an endangered species found on the Mongolian steppes today, is the last of the truly wild horses. All others on the planet are of a domesticated variety.
The researchers think that the population boons and busts throughout time may soon be explained by large scale geological and climate changes. In other words, tracking the evolution of the horse tells us a great deal more than just the history of horses. It can also tell us a great deal about the history of the planet and the evolution of man.