Those of you who spend much time around guides and outfitters know that from time to time, a small fib or a slightly embellished hunting story may pass through their lips. That’s why if I’d heard from my old buddy Larry Amos—a Colorado outfitter for a quarter century—that one of his pack mules had given birth, I would have just chalked it up as another of his whopper tales.

That’s before I saw the story in today’s Denver Post.Amosmule_3

Sure enough, a mule belonging to Amos, who operates Winterhawk Outfitters near Colbran, Colo., achieved a genetic impossibility and baffled scientists three months ago when it gave birth to a foal. Subsequent genetic testing has confirmed that Kate the pack mule is indeed the mother of the yet-unnamed youngster.

Here’s today’s News Hound science lesson: As a hybrid of two species–a female horse and a male donkey—mules have an odd number of chromosomes, rendering them sterile. A horse has 64 chromosomes and a donkey has 62. A mule inherits 63. An even number of chromosomes is needed to divide into pairs for reproduction to take place.

When he discovered the newly born foal in a corral this April, Amos (like many outfitters, a hard-core mule guy) knew he was witnessing something that science considered virtually impossible.

The Post story said that upon researching the occurrence, Amos and his wife, Laura found about 50 documented cases of mules giving birth in the last two centuries—and only two have been scientifically proven using DNA testing.

And those, friends, are some pretty incredible odds.

It’s an event so rare that the Romans had a saying, cum mula peperit, which translated means “when a mule foals.”

Its modern equivalent is “when hell freezes over.”

Or, “when you can believe everything a hunting outfitter tells you.”

I’m just kidding about the last one, Larry. Really.