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Archive for July, 2019

xolo

The dog world is always an interesting place to observe human behavior.  A few days ago, someone posted a coated Xoloitzcuintli (“Mexican hairless dog”) on an FB group, and I happened to mention the new evidence about the genetics of this dog breed.

This breed has a strong connection to the Mexica/Aztec identity in Mexico. The dog has a Nahuatl name, and when we discuss the Americas pre-Conquest, the civilization that existed in Mexico  was certainly the equivalent of anything in the Old World.

The mutation that causes hairlessness in these dogs has been traced to Mexico around 4,000 years ago. It is conferred by an incomplete dominant allele, and thus, it was able to spread from Mexico into South America, where hairless village dogs still exist in some areas.  Later, these hairless dogs were crossed with various toy breeds to found what has (laughably) been called “the Chinese crested dog.”

Further, we have really good evidence that shows that the indigenous dogs of the Americas were replaced with a genetic swarm of European dogs. This means that the xoloitzcuintli, though it has this mutation that originated in the Americas, is mostly European dog in its ancestry.

What is even more shocking is that a genome-wide analysis that traced the origins of many dog breeds found that the xolo fits in a clade that includes the German shepherd, the Berger Picard, and the Chinook. When a prick-eared regional Italian sheepdog called a Cane Paratore is added to the analysis, the xolo and the Peruvian hairless dog fit closer to that breed than the GSD and Picardy shepherd.

If one thinks about the history of Mexico, the Spanish became deeply involved in turning Mexico into a great place for herding cattle, sheep, and goats, and it would make sense that the typical dog that would have been brought over would have been an Iberian herding dog that is probably quite closely related to the Cane Paratore.

So more analysis was performed with an emphasis on Italian dog breeds. Some of the clades changed position, but xolos and Peruvian Inca orchid dogs remained in this clade closely related to the German shepherd, the various Italian herding dogs, the Berger Picard, and the Chinook.  The Catahoula leopard dog, a celebrated cur dog from Louisiana that is said to have derived from French and Spanish herding dogs brought over by colonists, were found to be closely related to the xolos.

This means that the dog called the xoloitzcuintli is mostly rough pastoral dog from the Iberian Peninsula, and it is not an ancient American breed.

I mentioned all this information on that Facebook group, and it was as if I blasphemed against the Almighty.

Sadly, we have almost lost an entire lineage of domestic dogs. The Conquest of the Americas and the resulting Columbian Exchange changed the genetic fortunes of humans and animals on these continents.

And though people would love for the xolo to be this untouched pure strain of dog. It simply is not.  In fact, it is very heavily admixed with southern European herding dog to the point that the dog is almost entirely that in ancestry. If that hairless trait were not dominant, it likely would have disappeared in the Mexican village dog population, and there would not have been any suggestion that these dogs were anything special.

So by a fluke of the allele, a mostly European herding dog-derived village dog from Mexico became the ancient dog of the Aztecs.

Yep. I ruined that one, too.

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quest fourth of july

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arctic fox crosses from Norway to Canada

The Guardian reports that an arctic fox has been documented walking 2,000 miles across the sea ice from Spitsbergen in the Svalbard Archipelago to Canada’s Ellesmere Island.

The vixen, a blue phase arctic fox, was collared with a tracking device on Spitsbergen. The Norwegian Polar Institute then followed her travels for the next 76 days. She wandered across the sea ice to Greenland, probably scavenging polar bear kills and catching sea birds. She then wandered across northern Greenland, eventually the sea ice again to settled on Ellesmere.

She traveled an average of 46.3 km per day, which is a little less than 29 miles day. On one day, she traveled  155 km or 96 miles across the ice sheet in Greenland.

Arctic foxes are significantly smaller than red foxes, which kill them where their ranges overlap.  The two species have hybridized in captivity, but the offspring are sterile. Arctic foxes are most closely related to the kit and swift foxes of North America, and they probably could produce fertile hybrids with them if they were ever given the opportunity.

Arctic foxes are not extremely dependent upon sea ice for survival, but the sea ice is useful for augmenting their diets in the winter, when they can follow polar bears.

Because it is unlikely that this fox’s journey is but a fluke, sea ice has been essential in retaining gene flow in the species across northern Eurasia and North America. More research must be performed on the genetics of this species, but it would surprise me if there wasn’t at least some gene flow across the arctic.

Arctic foxes are about the size of a toy dog, averaging 6-7 pounds in weight, but they are so well-adapted to long-distance travel that they can make such amazing journeys.

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