When it comes to heroic dogs, Balto is high on the list. The famous Siberian husky inspired a 1995 animated film and was immortalized as a statue in New York City’s Central Park for being part of a dogsled team that delivered lifesaving antitoxin to a remote Alaskan town that was struck by diphtheria in 1925. And now Balto’s DNA is offering new insight into how genetic diversity affects the health of dogs—past and present.

In a study published on Thursday in Science, biologists found that Balto’s genome is more diverse—and ultimately healthier—than that of most dog breeds today. His genes also suggest that he and his intrepid canine comrades in the 1920s had multiple traits that made them more fit to travel and survive in a harsh environment. The results reveal shifts over time not only in dogs’ genetics and ancestry but also in their genetic health.

“What we found is that Balto is more genetically diverse and genetically healthier than your breed dog of today but similar to those working Alaskan dogs that we have now—which is what you expect from a group that is still bred for work rather than the aesthetic phenotype that breed dogs are now held to,” says Katherine Moon, a postdoctoral researcher at the University of California, Santa Cruz, and co-lead author of the study.

Balto was part of an imported population of Siberian huskies bred for their speed, fitness and relatively small size. In January 1925 an outbreak of diphtheria (a serious bacterial infection that can be deadly if untreated, especially for children) was spreading in Nome, Alaska—a town that could only be reached by dogsled during the winter. Sled dog teams, including Balto’s, transported vials of diphtheria antitoxin in a 674-mile relay from Nenana, Alaska, braving intense winds and wind-chill temperatures of –85 degrees Fahrenheit. Using Balto as a representative of the 1920s Siberian huskies, Moon and her colleagues wanted to find out if that population had specific variations to their genes that made them such capable sled dogs.

The Lifesaving Sled Dog Balto Had Genes unlike Those of Dog Breeds Today
Musher Gunnar Kasson and his dog Balto are seen in close-up at the unveiling of a statue to honor Balto. Kasson led a dog team that saved many lives in Nome, Alaska, when he arrived there with diphtheria antitoxin. Balto was the leader of the dogs. Credit: Bettmann/Getty Images
When it comes to heroic dogs, Balto is high on the list. The famous Siberian husky inspired a 1995 animated film and was immortalized as a statue in New York City’s Central Park for being part of a dogsled team that delivered lifesaving antitoxin to a remote Alaskan town that was struck by diphtheria in 1925. And now Balto’s DNA is offering new insight into how genetic diversity affects the health of dogs—past and present.

In a study published on Thursday in Science, biologists found that Balto’s genome is more diverse—and ultimately healthier—than that of most dog breeds today. His genes also suggest that he and his intrepid canine comrades in the 1920s had multiple traits that made them more fit to travel and survive in a harsh environment. The results reveal shifts over time not only in dogs’ genetics and ancestry but also in their genetic health.

“What we found is that Balto is more genetically diverse and genetically healthier than your breed dog of today but similar to those working Alaskan dogs that we have now—which is what you expect from a group that is still bred for work rather than the aesthetic phenotype that breed dogs are now held to,” says Katherine Moon, a postdoctoral researcher at the University of California, Santa Cruz, and co-lead author of the study.

Balto was part of an imported population of Siberian huskies bred for their speed, fitness and relatively small size. In January 1925 an outbreak of diphtheria (a serious bacterial infection that can be deadly if untreated, especially for children) was spreading in Nome, Alaska—a town that could only be reached by dogsled during the winter. Sled dog teams, including Balto’s, transported vials of diphtheria antitoxin in a 674-mile relay from Nenana, Alaska, braving intense winds and wind-chill temperatures of –85 degrees Fahrenheit. Using Balto as a representative of the 1920s Siberian huskies, Moon and her colleagues wanted to find out if that population had specific variations to their genes that made them such capable sled dogs.

The researchers sequenced DNA samples from Balto’s taxidermied specimen at the Cleveland Museum of Natural History. They compared the sequences with those of current living dog breeds, including three 21st-century sled dogs that ran in the Iditarod—a modern annual dogsled race that traces some of the trails of the 1925 antitoxin run. Balto’s ancestry is not very dissimilar from that of today’s Alaskan sled dogs, with dogs of Arctic origin sharing 68 percent of his ancestry. He also shares a small amount of common ancestry with Asian dog lineages.