How to Build a Dog

Scientists have found the secret recipe behind the spectacular variety of dog shapes and sizes, and it could help unravel the complexity of human genetic disease.

The wearers are attendees of what is undoubtedly the world's elite canine mixer, one that takes place each year on the eve of the Westminster Kennel Club dog show. Tomorrow the nation's top dogs from 173 breeds will compete for glory across the street at Madison Square Garden. But today is more akin to a four-legged meet-and-greet, as owners shuffle through the check-in line at the competition's official lodgings. A basset hound aims a droopy eye across a luggage cart at a wired-up terrier. A pair of muscled Rhodesian ridgebacks, with matching leather leashes, pause for a brief hello with a fluffy Pyrenean shepherd. Outside the gift shop a Tibetan mastiff with paws the size of human hands goes nose to nose with a snuffling pug.

The variety on display in the hotel lobby—a dizzying array of body sizes, ear shapes, nose lengths, and barking habits—is what makes dog lovers such obstinate partisans. For reasons both practical and whimsical, man's best friend has been artificially evolved into the most diverse animal on the planet—a staggering achievement, given that most of the 350 to 400 dog breeds in existence have been around for only a couple hundred years. The breeders fast-forwarded the normal pace of evolution by combining traits from disparate dogs and accentuating them by breeding those offspring with the largest hints of the desired attributes. To create a dog well suited for cornering badgers, for instance, it is thought that German hunters in the 18th and 19th centuries brought together some combination of hounds—the basset, a native of France, being the likely suspect—and terriers, producing a new variation on the theme of dog with stubby legs and a rounded body that enabled it to chase its prey into the mouth of a burrow: hence the dachshund, or "badger dog" in German. (A rival, flimsier history of the breed has it dating back, in some form, to ancient Egypt.) Pliable skin served as a defense mechanism, allowing the dog to endure sharp-toothed bites without significant damage. A long and sturdy tail helped hunters to retrieve it from an animal's lair, badger in its mouth.

The breeders gave no thought, of course, to the fact that while coaxing such weird new dogs into existence, they were also tinkering with the genes that determine canine anatomy in the first place­. Scientists since have assumed that underneath the morphological diversity of dogs lay an equivalent amount of genetic diversity. A recent explosion in canine genomic research, however, has led to a surprising, and opposite, conclusion: The vast mosaic of dog shapes, colors, and sizes is decided largely by changes in a mere handful of gene regions. The difference between the dachshund's diminutive body and the Rottweiler's massive one hangs on the sequence of a single gene. The disparity between the dachshund's stumpy legs—known officially as disproportionate dwarfism, or chondrodysplasia—and a greyhound's sleek ones is determined by another one.

Read This Next

Soils found in Antarctica seem to contain no life

The complex situation for immunocompromised people and COVID-19 vaccines

Champions of wildlife and wild places win prestigious awards

Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet