Mules are pretty amazing. In this very special LFPL Teen Blog post, we’ll explore key points of history and biology – as well as thorny ethical issues – all at the same time through the lens of these famous hybrid equines. (Language warning? Or something. It’s all clean in context, but we do need to talk extensively about donkeys, especially jacks.)
The Definition of a Species
A species is all of the living things that can make babies together, whose babies can also make babies without any problems like diminished fertility. That’s it. Easy, actually. That’s why a gray wolf and a toy poodle are members of the same species, even though they look so different. Wolfdogs are a thing, and absolutely can go on to have lots of puppies. Like so:

By Venpia (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
This brings us to equines (the horse family) and mules.
Introducing Mules
There are lots of equine hybrids, actually. You may have heard of mules, hinnies, and even zorses, but one of my favorite equine hybrids is the otherwise fairly rare and obscure zebroid stallion zebra X jenny donkey hybrid, called either a zedonk, a zebronky, a zonkey, or a zebrass.

By Whitney Carpenter. [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
Mules, though, were wildly popular, and continue to be the most commonly bred equine hybrid. They’re reliable to breed, and generally have the best traits of both horses and donkeys. Horses are fast, but tend to panic. Donkeys are strong and sensible, but are usually smaller than horses. A mule (if you choose the parents wisely) can be in the size range of a horse, strong, fast, and sensible. A mule is the offspring of a male donkey, and a female horse. To make all this easier to understand without too much typing, here’s some basic terms!
Horses:
Baby horse – foal
Immature female horse – filly
Immature male horse – colt
Mature female horse – mare
Castrated male horse – gelding
Mature male horse – stallion/horse (We call all horses horses, even though technically it’s just the stallions that are horse horses. Just like we call all cows cows, even though it refers to specifically female cows, which is kind of redundant. Similarly to dogs: only male dogs are dog dogs. I’ll probably do a whole post on the English language and all our weird animal terms. Also, different breeds take different amounts of time to grow up, so the exact years in which a horse is a filly vs a mare or colt vs stallion can change, depending on the breed. Just like humans take different amounts of time to hit puberty or something. Some breeds are just late bloomers, or early ones, depending.)
Donkeys / Asses:
Baby donkey – foal
Female donkey – jennet / jenny
Male donkey – jack
Castrated male donkey – john / gelding
To get a mule, breed a mare to a jack. That’s much easier to say.
Mules
Baby mule – foal
Female mule – molly
Intact male mule (super rare – why put up with behavior issues if they’re sterile anyway?) – horse mule
Castrated male mule – john mule
The trick with mules is that most jacks are tiny, since most donkeys are also tiny. This is about average size for a regular donkey:

By Rod Waddington from Kergunyah, Australia (Oromo Woman, Ethiopia) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
The Famous Poitou Mule
In France over the 18th and 19th Centuries, mules were so important to agriculture that an entire breed of horse AND an entire breed of donkey were developed purely so that farmers could get large, strong mules to pull their farm equipment.
This is a Poitou Horse, or a Poitevin Mulassier (Poitou Mule-maker):

By Poitou (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
There’s also the Poitou Donkey, a giant-sized breed with a long shaggy coat. This is a jennet and her foal at a show:
Again, since the jacks are the ones that people use to make mules, jennet Poitou donkeys are also living gene banks, like stallion Poitou horses.
So, that’s two breeds (each from a different species) of equine, each selected over time just for making mules. When you do breed a Poitou donkey jack to a Poitou horse mare, you get a gorgeous, versatile Poitou Mule:

By Eponimm (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

By Eponimm (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

By Eponimm (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

By Eponimm (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
The Ballad of Idaho Gem / Idaho Star / Utah Pioneer
The setup: cutting-edge science, a wealthy entrepreneur who will “spare no expense” in pursuit of his passion, and a potentially lucrative payoff. This story isn’t a novel or a movie about what could happen with cloning technology. It’s about what did happen, over a decade ago, with the first batch of cloned equines.
Don Jacklin, the President of the American Mule Racing Association, wanted a way to reproduce his best racing mule. Since mules are sterile, this meant enlisting the aid of a crack team of equine reproduction scientists and veterinarians, and cloning his champion mule. Idaho Gem, Idaho Star, and Utah Pioneer were the genetically identical results of this successful quest to clone the first equine. Technically, due to being born first, Idaho Gem was the official first equine clone.
So, as clones of a champion racing mule, did the three duplicates go on to dominate the sport? Interestingly, no. Idaho Star apparently never was that into running, Utah Pioneer remains an educational exhibit entertaining schoolkids, and Idaho Gem – although good at racing – didn’t live up to Jacklin’s expectations as a champion. He eventually retrained for gymkhana.
I guess it makes sense, really, that clones of the original aren’t like the original exactly. After all, the three cloned mules are effectively identical triplets of each other, and identical siblings can be very different from each other in all sorts of ways, including personality.
Genetics literally isn’t everything, and it certainly isn’t destiny.