Curiosities of Hybrid Equid History

Contents:

• Part I: Lord Morton's Mare
• Part II: The Kunga
• Part III: George Washington's Mules
• Bonus Part: The Zonkeys of Tijuana

Mule competing at the U.S. Dressage Finals
Image credit: Horse Illustrated

Despite playing an important role in the history of many cultures from ancient times to the modern day, hybrid equids rarely get the credit they deserve for their contributions to humankind. While you are probably aware of the mule (Equus caballus × Equus asinus) and its significance as a draft, pack, and riding animal, you might not be aware of how it, and its hybrid equid cousins, have shaped history.

The short blips in history that you are about to read highlight how equid hybrids have influenced humanity, however, they do not tell the full story. I highly encourage the reader to do their own further research on this interesting topic. Nonetheless, if you win Jeopardy (or family trivia night) because I taught you that George Washington had an obsession with mules, I would like the credit!

Part I: Lord Morton's Mare

Before Mendelian inheritance* was accepted by the scientific community in the late 19th century (recall the dreaded Punnett squares** from your middle school science classes), many theories regarding the nature of heredity were given credence by prominent researchers. Telegony was one of these theories, originally proposed by Aristotle. Telegony describes the idea that the offspring of a female can inherit traits from her previous mates (i.e. not only the father but also prior sexual partners). It doesn't take a genius to reason that this doesn't really make physiological sense but in the mid-19th century, it was considered to be a legitimate hypothesis.

In fact, Charles Darwin included telegony in his 1859 book, On the Origin of Species. Darwin cited the example of Lord Morton's mare in his book, marking this hybrid equid as an important contributor to evolutionary theory.

Quagga in the London Zoo
Image credit: Encyclopedia Britannica

Lord Morton's mare was a chestnut Arabian mare who gave birth in the early 19th century to a cross between the quagga and the domestic horse (Equus caballus × Equus quagga quagga). (Note: the quagga is an extinct subspecies of the plains zebra, although at the time it was believed to be a distinct species due to its unique coloring.) Subsequently, the broodmare was bred to a black Arabian stallion. The foals resulting from this pairing had black striping on the legs similar to the hybrid. After finding this, Lord Morton published these findings alongside his conclusion that the quagga's traits had been passed on to the mare's subsequent offspring, supporting the theory of telegony.

Hybrid filly born to Lord Morton's mare
Image credit: Wikipedia

Today, telegony is regarded as a pseudoscientific theory. Now we know that Mendelian inheritance was responsible - both the mare and the stallion likely carried recessive genes that coded for the striped leg pattern and passed that trait along to their progeny, despite neither of them possessing that phenotype. Rejecting hypotheses, of course, is an essential part of the scientific process, and the hybrid equid in this story is still discussed as an important contributor to the field of biology.

Minecraft mule
Image credit: Minecraft Wiki

FUN FACT BREAK: Did you know there are mules in Minecraft? In Minecraft, mules can be bred by crossing a donkey and a horse. Much like in real life, the resulting hybrid is sterile!

Part II: The Kunga

The kunga was a hybrid equid bred in ancient Mesopotamia for draft, war, and ceremonial purposes. Kungas were a cross between a female domestic donkey and a male Syrian wild ass (Equus asinus × Equus hemionus hemippus). Today, the kunga is regarded as the first animal to be bioengineered by humans, marking a major advancement in the history of humanity.

Watch the following video to learn more:

FUN FACT BREAK: Did you know that equid species vary greatly in chromosome number? These range from 32 chromosomes in the mountain zebra to 66 in the Przewalski's horse. Despite this, likely all equid species are capable of interbreeding (most resulting in sterile hybrid offspring).

Part III: George Washington's Mules

"Pedro Tellez and Royal Gift arriving at Mount Vernon, 1785"
Image credit: Raúl Miguel Barroso (2019)

President George Washington believed strongly in the mule's potential as the animal to build America. Spanish donkeys, which were at the time considered to be the superior breeds for breeding mules (and, by many, are still today), had not yet made it to America. Washington believed that the introduction of these jacks would drastically improve America's mules and, in conjunction, its agricultural output.

Unfortunately for the future president, obtaining Spanish jacks would prove harder than it may seem. These jacks were illegal to export from Spain without royal approval, meaning Washington had to get in contact with the King of Spain, Charles III. In 1784, after four years of unsuccessfully schmoozing through agents sent to Spain, King Charles III gifted Washington two jacks.

Mule plowing on a South Carolina farm, c. 1940s
Image credit: Columbia Metropolitan

Only one jack, aptly named Royal Gift, survived the journey to Mount Vernon. He, and his progeny, bred American mares and expanded mules across the new country. Later, Washington was gifted a Maltese donkey that was included among his mule-breeding stock. These European donkeys were much larger and stronger than the donkeys previously available, creating mules that could work as hard as horses on less feed and water. Fifteen years after Royal Gift's arrival, there were 60 mules working at Mount Vernon.

Today, President Washington is widely credited with creating the foundation for the American Mammoth Donkey, the breed that is used to produce most mules today. A lot of America, especially in the Southern and Western states, was built with the help of the large mules that Washington promoted. 

Disneyland mules c. 1955
Image credit: Yesterland

FUN FACT BREAK: Did you know that, at its opening in 1955, Disneyland's Frontierland hosted an attraction in which guests could ride mules? The Pack Mules attraction lasted until 1973. Today, the space where the mules used to roam is home to Big Thunder Mountain Railroad.

Bonus Part: The Zonkeys of Tijuana

"Zonkey" typically refers to a cross between a donkey and a zebra. (Bonus fun fact: "Zonkey" and "zedonk" were recently added to the official Scrabble dictionary! Have fun winning your next game of Scrabble.) In Tijuana, Mexico, however, a zonkey is just a donkey painted or dyed to appear to have black stripes. So, yes, this bonus section is not, in fact, about hybrid equines. Zonkeys are a common part of the tourist experience in Tijuana - they stand, often clad in stereotypically Mexican attire in front of a stereotypically Mexican backdrop, waiting for visitors to take pictures with them.

Tijuana "Zonkey" eating on the street
Image credit: Los Angeles Times

Tijuana zonkeys possess a significant cultural role in the area and are noted as being highly symbolic of the area. I mention them not only because their existence is a fun piece of trivia, but also because they highlight the intrigue and excitement that humans have exhibited, and continue to exhibit, about equid hybrids. Humans, from ancient Mesopotamian kings to George Washington and even Walt Disney, have been fascinated by equid hybrids for centuries. Their legacy continues to the modern day - when many still rely on their equid hybrids for survival - and others take their mules to the U.S. Dressage Finals.

*Mendelian inheritance describes the inheritance of traits controlled by one gene. In Mendelian inheritance, each parent passes on one allele, and traits are determined by dominant or recessive alleles. An example in horses is the gray gene. If one parent passes on the dominant allele, the baby will be gray. An example of non-Mendelian inheritance is height, which is controlled by multiple genes (polygenic).

**A Punnett square is a simple diagram used to predict the genotype of a certain cross - essentially, a visual depiction of Mendelian inheritance.

References

Bennett, E.A., Weber, J., Bendhafer, W., Champlot, S., Peters, J., Schwartz, G.M., Grange, T., Geigl, E.M. (2022). The genetic identity of the earliest human-made hybrid animals, the kungas of Syro-Mesopotamia. Science Advances, 8(2). https://doi.org/10.1126/sciadv.abm0218.

Coe, A. (2020, February 12). George Washington saw a future for America: Mules. Smithsonian Magazine. https://www.smithsonianmag.com/history/george-washington-saw-future-america-mules-180974182/

Dolce, R. (2014). Equids as luxury gifts at the centre of interregional economic dynamics in the archaic urban cultures of the Ancient Near East. Syria Archéologie, Art et Histoire, 91, 55-75. https://doi.org/10.4000/syria.2664

Endersby, J. (2007, September 14). Equus quagga and Lord Morton’s mare. The Guardian. https://www.theguardian.com/books/2007/sep/14/firstbookaw.gurardianfirstbookaward8

Mount Vernon. (n.d.). Royal Gift (Donkey). George Washington’s Mount Vernon Digital Encyclopedia. https://www.mountvernon.org/library/digitalhistory/digital-encyclopedia/article/royal-gift-donkey/

Kimura, R., Masuda, M., Sheth, F., Sheth, J.J. (2005). Assessment of the traditional production of the hybrids of Indian wild asses (Equus hemionus khur) and jennies (Equus asinus) in Kutch, Gujarat. Journal of Environmental Systems, 32(4), 275-289. https://doi.org/10.2190/ES.32.4.a

Joshi, C.G., Rank, D.N., Jani, R., Tank, P.H., Brahmkshtri, B.P., Vataliya, P., Solanki, J.V. (2001). A case of E. asinus X E. heminous Khur hybrid. The Indian Veterinary Journal, 78(6). https://www.researchgate.net/publication/36447482_A_case_of_E_asinus_X_E_heminous_Khur_hybrid

Miranda, C.A. (2015, November 15). From the archives: How the zonkey got its stripes: Long before Instagram, Tijuana’s tourist donkeys were camera-ready. Los Angeles Times. https://www.latimes.com/entertainment/arts/miranda/la-et-cam-story-behind-tijuana-zebra-striped-donkeys-20151106-column.html

The Livestock Conservancy. (n.d.). American Mammoth Jackstock. https://livestockconservancy.org/heritage-breeds/heritage-breeds-list/american-mammoth-jackstock-donkey/

TRTWorld. (2022). Kunga: The first animal to be bioengineered 4,500 years ago. https://www.trtworld.com/life/kunga-the-first-animal-to-be-bioengineered-4-500-years-ago-53744

Weiss, W. (2023, March 31.) Mule Pack, Rainbow Ridge Pack Mules, and Pack Mules Through Nature’s Wonderland. Yesterland. https://www.yesterland.com/earlymules.html