Balto’s DNA Provides a New Look at the Intrepid Sled Dog

In early 1925, a relay of sled dog teams carried a lifesaving serum to the town of Nome, Alaska, where a diphtheria outbreak was spreading among children. The dogs and drivers transported the medicine 674 miles through gale force winds and whiteout conditions. They reached their destination in less than 5.5 days, making the delivery without a single broken vial.

One of the dogs, Balto, remains famous to this day, living on through animated films and a Central Park statue.

Now, scientists have immortalized the intrepid sled dog’s legacy in a new way—in a study published Friday in the journal Science, researchers analyzed his DNA. The study compares his genomic data to that of nearly 700 other dogs, as well as a new collection of mammalian genomes, to learn more about Balto and compare him to modern canines.

The study is one of 11 new papers analyzing data from a mammalian genome collection called Zoonomia, which contains the complete set of genetic material for 240 mammalian species. From here, researchers aim to identify the specific genes that mammals share—and hopefully learn more about ourselves.

“They will be an amazing resource for future studies,” Tatiana Feuerborn, a paleogeneticist at the National Human Genome Research Institute (NHGRI) who wasn’t involved in the work, tells Science’s Elizabeth Pennisi.

“This is really an unprecedented view of the evolutionary history of mammalian genomes,” Maria Chikina, a computational biologist at the University of Pittsburgh who did not contribute to the research, tells the Washington Post’s Mark Johnson and Dino Grandoni. “We now know which parts of the genome are important in building a mammal.”

As for Balto, researchers sequenced his genome using DNA from his taxidermy remains at the Cleveland Museum of Natural History. They then compared his DNA to genetic material from a range of other canines, including wild species, contemporary sled dogs and various breeds. His genes provide a window into an era before humans bred dogs to look a certain way.

They found that Balto was genetically diverse and shared only part of his DNA with modern Siberian huskies. He was less inbred than today’s dogs, which could explain why he had fewer genetic mutations that might cause health problems, writes the New York Times’ Emily Anthes.

“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 [physical traits] that breed dogs are now held to,” Katherine Moon, a co-author of the Balto study and a genomicist at the University of California, Santa Cruz, tells Scientific American’s Lauren J. Young.

The researchers were also able to predict Balto’s appearance from his DNA. His genome suggested that he was 21.7 inches tall at his shoulders and had a double-layered coat of fur that was mostly black with a bit of white. The predictions match historical photographs and the taxidermy remains, according to the paper.

In this way, Balto provides a rare case in which researchers can actually check the original specimen see if their conclusions based on DNA are accurate. “It was great to be able to see that phenotype that we predicted from his genotype is sort of consistent with what we knew about Balto already,” Moon tells Scientific American.

In some ways, Balto was a specimen in between wolves and modern dogs—the researchers found he had a greater ability to digest starch than wolves and Greenland sled dogs do, but he was less capable at starch digestion than modern breeds are. Lots of commercial pet foods today contain starch, according to the Washington Post.

Balto also had genes that would have helped him build strong bones and muscles for pulling sleds, according to Science.

The breadth of work done with Balto’s genome is “extraordinary,” Elaine Ostrander, a dog geneticist at NHGRI who did not contribute to the study, tells Science. “It gives us a very clear picture of dogs who were selected for [sled dogs] at that point in time.”

Balto’s genome, along with those of the other mammals in Zoonomia, could help scientists uncover new knowledge about a wide range of creatures. Balto’s genes could be a blueprint for promoting healthier dogs today, Ostrander tells Science. And the mammalian genomes could provide insights about the evolution, special behaviors and vulnerability to extinction of other species, writes the Times.

The sequenced genomes will be publicly available so that other researchers can build on that knowledge, according to Inverse’s Elana Spivack.

“I hope people use [the data] for a million and one applications,” Moon tells Inverse. “I think one of the coolest things about genetics is that every time we step forward, we step forward as a group.”

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.