Sulphur Mustangs: The Northern Iberian links

A Sulphur Mustang.
A Sulphur Mustang. © Dr Mitch Wilkinson

Dr Mitch Wilkinson, in the third part of his series on the Sulphur Mustangs, explores their ties to Northern Iberian horses.

In a 2016 article, The Legacy of Columbus in American Horse Populations Assessed by Microsatellite Markers, New World Criollo horse populations were compared to Old World horse groups. Criollo means descended from Iberian stock but born in the New World.30

The Legacy of Columbus study was extensive and included 27 Criollo breeds from 12 North and South American countries.  It compared the Criollo breeds to 19 Iberian breeds, such as the Moroccan Barb, Thoroughbred, and Arabian. Distinguished scientists in the field of equine genetics conducted the study. Scientists including Dr Phillip Sponenberg and Dr Jose Vega-Pla were involved.

American Mustangs were included in the study as Criollo horses. The American mustangs were not categorized by group. The results concluded that Criollo horses had a close relationship with breeds from the southern Iberian Peninsula, but the Celtic group of horses from Northern Spain had one of the most profound influences. The results indicate that Criollo breeds have a common ancestry, but each has become its distinctive breed over time. The Legacy of Columbus study found that the contribution of Iberian and Middle Eastern horse breeds to modern Criollo populations in North and South America was around 50% Northern Iberian Celtic pony, 30% Southern Iberian, and 20% Arabian-Thoroughbred.30 These findings correlate with the findings in this study.

The historical records of the first horses from Spain to the New World show that Southern Iberian horses were the first imports. Many of these horses would fit the modern definition of a Spanish Jennet, but not all. Records of the importation of small-statured horses such as the Galician horse (Cabalo Galego) and the Garrano from northern Portugal remain elusive. As discussed earlier, the “Reconquista” of Spain from the Moors was spearheaded by the kingdom of Castille in northern Spain, where Celtic ponies reside.

One of the few records that exist shows that in 1508, the Spanish authorities authorized the transport of 40 northern Spanish Celtic ponies for the expedition organized by Alonso Qjeda and Diego Nicuese to Panama. These animals were designated as workhorses. Horses like these can be ridden but are mainly used for packing goods. A young Francisco Pizarro was a member of the expedition.

The Celtic horses were procured in Spain before the expedition set sail.24 Unfortunately, the Ojeda-Nicuesa expedition, whose purpose was to found a colony near present-day Panama, was a total failure. The fate of the horses is unknown. Although the 40 Celtic ponies may not have contributed to the development of New World horses, historical records show that imports of such horses were happening at that time. This early expedition to the mainland was 11 years before the Cortés expedition to conquer the Aztecs.

Another curious type of indigenous Mexican horse called the Galiceno is genetically very close to the Galician horse. The origin of the Galiceno is shrouded in legend. It has been stated that the Galiceno horse is descended from the first 16 horses brought to Mexico by Cortés in April of 1519 when he established the city of Veracruz. Unfortunately, all these horses died, as stated earlier. Therefore, the Galiceno horse likely descended from later imports of Celtic-type horses that might have been imported from Spain to Hispaniola, Jamaica, Cuba, or directly to the mainland. All the Spanish islands played predominant roles in the conquest of Mexico. So the question is, “Could northern Iberian horses have been imported to the West Indies during colonial times”, even though historical records are lacking? Records need to be located as to the nature of horses imported if they exist. Cortés may have imported work animals directly from Spain during the conquest, but that is unlikely due to expense.

Hernan Cortez’s home in Veracruz, Mexico.
Hernán Cortés’s home in Veracruz, Mexico.

Another possibility that led to the introduction of Celtic pony bloodlines is the origin of the Jennet itself in southern Spain. Could the Moorish breeding programs have incorporated horse blood from northern Spain?

Although the kingdoms of Northern Spain, like Castille, were never conquered, there was trade between Muslims and Christians through the centuries. Without a doubt, horses were traded. Galician ponies are known for having “gait”. Could the Moorish breeders have incorporated Galician ponies into their breeding programs to secure gait in Jennets? Again, we are awaiting archeological samples to test this theory.

At one time, there was a large population of Galiceno horses in Mexico. Many were feral. Sadly, they are almost extinct today. However, history shows that the Galiceno horse may represent a similar horse to those bred on early Mexican horse breeding farms. Cortés probably played a role in Galiceno horse creation, but his first 16 horses to the mainland of Mexico did not.

Fig. 9: Graph showing the relationship between populations of Sulphur Mustangs, Galician horses of northern Spain, and Mexican Galiceno horses.
Fig. 9: Graph showing the relationship between populations of Sulphur Mustangs, Galician horses of northern Spain, and Mexican Galiceno horses.

Regardless of the origin, genetic analysis shows that northern Iberian Celtic horses were incorporated into all the Criollo breeds in North and South America.30 PCoA analysis of Sulphur Mustangs, Galician horses, and Mexican Galiceno horses show a very close relationship with overlapping areas of the plots for each population. The graph above shows the connections.

Left: A Galician Pony; and at right, a Galiceno Horse.
Left: A Galician Pony; and at right, a Galiceno Horse.
A Sulphur Mustang.
A Sulphur Mustang. © Dr Mitch Wilkinson

It can be seen in the photos above that the basic conformation of the three horses is similar. Numerous studies have shown the genetic relationship between groups. The conclusion is that in addition to being related to the now-extinct Spanish Jennet of the 15th century, some components of the northern Iberian Celtic pony also went into the heritage of the Sulphur horse and related Spanish Colonial equines. If the Legacy of Columbus study is any indication, the Celtic pony influence on the future Sulphur Mustang may have been more significant than the Southern Spanish Jennet or ancestral Marismeno.

How and when these bloodlines were introduced into the Sulphur population, and so many other Criollo horse types, can’t be determined.

Fig. 10: Comparison of head shape between Grand Turk Island, Northern Iberian Galician Pony, Baca, Wilbur-Cruce, and Sulphur Mustang. Note: Andalusian and Lusitano have similar head shapes.
Fig. 10: Comparison of head shape between Grand Turk Island, Northern Iberian Galician Pony, Baca, Wilbur-Cruce, and Sulphur Mustang. Note: Andalusian and Lusitano have similar head shapes.


Spanish breeding farms of the West Indies develop a new strain of Iberian Horse

Initially, on the Island of Hispaniola and later on Puerto Rico and Jamaica, mixtures of Iberian horses were being bred. We may never know all the components, but we can discern the major elements between historical records and genetic analysis.

First, we have the Spanish Jennet, which progenerated the modern Andalusian and Lusitano. The Jennet was probably the finest horse of its period. In addition, a component of the ancestral Marismeno horse of the Guadalquivir marshes was added. We know the Marismeno contribution by tradition, historical records, and the presence of the mtDNA haplogroup A542c,666A, which is found in the semi-feral Marismeno horses, American Spanish mustang populations, and South American Criollo horse populations.24 Lastly, a large portion of the Northern Iberian Celtic pony must have been added because of the continued appearance of genetic evidence found in modern Criollo horse populations and some American mustangs implicating Celtic horse ancestry. No historical records corroborate the importation of Northern Iberian Celtic horses. Still, the close relationship of the Mexican Galiceno horse to the Galician Pony of Northern Spain is more than just the name. Genetic studies, including this one, have shown the relationship between the Mexican and Spanish Celtic horse populations. These same populations seem to have a relationship with Sulphur mustangs (see Fig. 9 above).

The horses created on different islands, in multiple island breeding farms, and at different times, were not homogenous. Each breeding operation had its own particular goal. The fact that limited types of horses were available for shipment to the new Spanish colonies precluded a wide variation in types.

We could call this new type of horse created on Caribbean island breeding farms the Caribbean Criollo. Versions of this horse from Hispaniola and Jamaica started the first mainland breeding farms near Mexico City after the defeat of the Aztecs in 1521. As other tribes were subdued throughout Mexico, the horse and Spanish civilization followed. Eventually, the Spanish arrived in what is now Northern Mexico. Consequently, Spaniards and their horses populated New Mexico, California, and the southwestern United States. These were the ancestors of Sulphur Mustangs, Baca horses, Wilbur-Cruce horses, and others not currently identified. Their Caribbean cousins still exist in isolated island pockets. Horses found on Grand Turk Island are similar, but all groups have followed their own development over the past 500 years.

After Mexico was subdued, Colombia, Venezuela, and Peru were conquered and settled with Spaniards and their horses. However, most South American countries were occupied by a mixture of horses from both the Caribbean and directly from Spain and Portugal. Today, the northern Iberian Celtic pony, the Spanish Jennet, and the Marismeno influence still exist in the bloodlines of South American Criollos, but in different proportions than in American Spanish Colonial breeds.30

» Next: The historic links to North Africa


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One thought on “Sulphur Mustangs: The Northern Iberian links

  • May 27, 2023 at 10:35 am

    Again excellent compilation and tracing back the history of the Sulphur mustangs based on historical and genetic evidence. Fascinating that the Celtic Iberian horses is revealed to be such an important part of the ancestry of the Sulphur mustangs. I lived and worked in Colombia as a wildlife ecologist for a few years. Their horse culture is alive and well and I remember attending their “Ferias de Equitacion” in such places as Manizales.


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