Edward was a mule who famously surprised the scientific community in the 1920s by giving birth to two foals. As a mule, Edward was expected to be sterile, yet somehow managed to reproduce. Mules are the hybrid offspring of a male donkey and female horse, and are generally considered incapable of producing viable offspring themselves. However, Edward’s case shows that mules reproducing is rare but not impossible.
What is a mule?
A mule is the offspring of a male donkey (jack) and a female horse (mare). Mules inherit traits from both parents, having the hardy body, sure-footedness and stamina of the donkey, along with the stronger back, higher intelligence and faster pace of the horse.
| Parent 1 | Male Donkey (Jack) |
| Parent 2 | Female Horse (Mare) |
| Offspring | Mule |
Mules are almost always sterile, meaning they cannot produce viable offspring themselves. This is due to having an odd number of chromosomes, which prevents the chromosomes from pairing up properly during meiosis. A normal horse has 64 chromosomes while a donkey has 62 chromosomes. When they mate, the mule ends up with 63 – an uneven number that cannot divide evenly during reproduction.
Why are mules usually sterile?
Mules have 63 chromosomes due to their mixed parentage, whereas horses have 64 chromosomes and donkeys have 62. During meiosis, the cell division process that produces sex cells like sperm and eggs, each parent donates half their chromosomes to the offspring. For reproduction to be successful, the chromosomes donated from each parent need to pair up properly.
| Animal | Number of Chromosomes |
| Horse | 64 |
| Donkey | 62 |
| Mule | 63 (32 from horse + 31 from donkey) |
With their uneven number of 63 chromosomes, mules end up with unpaired chromosomes during meiosis, leading to the production of abnormal and non-viable sex cells. This results in mules being sterile and unable to reproduce, with extremely rare exceptions.
The exceptional case of Edward the Mule
In the 1920s, a mule named Old Beck gave birth to two foals in Colorado. This was an exceptional event, given the sterility of mules. Old Beck was owned by a farmer named Ubo Eichorn who later changed the mule’s name to Edward.
Edward was sired by a jack named Ned and born to a mare that Eichorn owned. Despite Edward’s mixed parentage and odd number of chromosomes, he was able to sire two healthy foals with two different mares from Eichorn’s farm.
The two foals, named Utah Pioneer and Idaho Pioneer, both went on to lead long and healthy lives themselves. Utah Pioneer lived to be 25 years old and Idaho Pioneer lived to be 28 years old.
Edward’s foals
| Name | Mother |
| Utah Pioneer | Mare owned by Eichorn |
| Idaho Pioneer | Different mare owned by Eichorn |
Edward’s ability to reproduce caught the attention of scientists and led to new insights into mules and reproduction.
Scientific Explanations
Edward’s remarkable case led to much interest from geneticists and the scientific community in understanding how he was able to overcome hybrid sterility and reproduce. Several theories emerged:
Chromosomal Translocation
One theory is that Edward may have had a chromosomal translocation, meaning that some of his chromosomes were fused or rearranged. This could have resulted in him having an even number of chromosomes, enabling successful chromosomal pairing and reproduction.
Genetic Mosaicism
Another possibility is genetic mosaicism – Edward may have been a mosaic mule that had some cells with a normal chromosomal makeup alongside some hybrid cells. This could have enabled him to produce some viable reproductive cells.
Parthenogenesis
Some scientists proposed parthenogenesis as an explanation – that Edward reproduced asexually without a female mate, resulting in offspring that were genetic clones. However, this was ruled out as Edward’s foals had traits distinct from Edward himself.
Back-crossing in Parents
It was also suggested that Edward’s parents may have had some cross-breeding further back in their lineage that made their own genetic makeup compatible for reproduction. This could have enabled Edward to inherit a chromosomal makeup with an even number of chromosome pairs.
Later Examinations
Decades after Edward amazed the world, his preserved hide was sent in the 1960s to the University of California Davis for examination. Cytogenetic analysis found that Edward did indeed have 63 chromosomes, ruling out theories that he had an even number.
However, the analysis was unable to determine conclusively why Edward was fertile. The mechanisms behind Edward’s miraculous reproduction remains somewhat of a mystery to this day.
Significance of Edward the Mule
While extremely rare, Edward’s case shows that mules reproducing is biologically possible, albeit under special genetic circumstances that defy the odds.
Some key impacts of Edward’s remarkable case:
Advancement of Genetics
Edward furthered scientific understanding of animal reproduction and genetics, shedding light on how hybrid sterility can sometimes be overcome.
Proof of mule fertility
Edward proved that mules are not absolutely 100% sterile, opening up further research into reproductive anomalies.
Increased mule demand
Edward created a frenzy of interest in fertile mules, greatly increasing mule prices as buyers hoped to own another rare fertile specimen.
Other fertile mules
While extremely uncommon, a handful of other fertile mules have been recorded both before and after Edward:
1876 – Jim the Mule
Jim the Mule produced a foal named Telegraph in Iowa in 1876.
1945 – Krause’s mule
A mule owned by Hans Krause of Germany mated with one of his mares in 1945, producing a foal.
2015 – Maple’s Marvel
A mule mare named Maple produced a foal sired by a donkey jack in Colorado in 2015. Genetic testing confirmed the foal was indeed Maple’s.
However, these cases all number among the rarest of anomalies, with mules overwhelmingly being sterile. Edward remains the most famous case capturing public imagination about the possibility of fertile mules.
Conclusion
Edward the Mule demonstrated that the reproductive barriers between horses and donkeys can rarely be overcome, albeit under special genetic circumstances. His ability to reproduce despite his hybrid nature defied expectations and advanced scientific knowledge.
While the mechanisms behind Edward’s fertility remain murky, his case continues to fascinate as an extraordinary example of hybrid vigour exceeding the limits imposed by hybrid infertility. Edward left a legacy that mules should not be defined absolutely by their sterility. With the right genetic conditions, a few exceptional mules may retain fertility and achieve what was thought impossible.