Io and Frank

Dogs are the most varied species of mammal on earth, largely because of us. Thousands of years of intimate association with humans means some were bred to chase small animals into dens (Io, who has some serious Dachshund genes, is of this blanket-burrowing ilk), while others are perfectly suited to retrieving ducks from frigid lakes (Frank’s coat is too thick to see his skin, and he jumps into every body of water he can, even when he has to break ice). The variation isn’t just physical—any dog owner knows that whether or not their pet will embarrass them in a given situation owes as much to personality as to training efforts.

That variation is part of why canine research is growing. Dogs are susceptible to many of the same ills as humans—from Lyme to cancer to diabetes—and go home at night with their owners, eliminating the ethical and regulatory complexities of housing them in a lab. Human and canine genetics have much in common; Io’s stubby 6-inch legs are likely the result of the same family of genes that regulated my bone development. Finally, there’s a pawsitive plethora of research subjects: 65 million U.S. households include one. “We have a responsibility to deeply understand these animals if we’re going to live with them,” Monique Udell, who directs the human-animal interaction lab at Oregon State University, told the New York Times. “We have this great potential to learn a lot about them and a lot about ourselves in the process.”