For over a decade, my family shared our home with a short, fat beagle named Kayla Sue. She had big floppy ears, a tail as straight as an exclamation point, and a coat of fur that was a patchwork of white, brown, and black splotches. Her love of chasing small animals was matched only by her enthusiasm for eating, napping, and belly rubs. One of my best friends growing up, on the other hand, had a mean-spirited Dachshund named Rocky who would not let anyone outside his family touch his long, brown, sausage-shaped body. Meanwhile, one of my brother’s close childhood friends had two humongous, overly-friendly, black-and-brown German shepherds that would immediately bowl you over when you walked through the front door.
It doesn’t take a particularly sharp observer to notice that, despite being the same species, the more than 300 breeds of dog have remarkably different physical and behavioral traits. But what remains less clear even today are the specific biological roots that produce these widely varying attributes. And, perhaps more importantly, scientists seek to understand how learning about that immense diversity might help us improve the health of our canine companions – and ourselves.