The Secret History of Dogs

Why do collies have smooth, silky hair while poodles have cute curls? What gives a pooch spots, swirls, or stripes? And how did Great Danes get to be 40 times bigger than Chihuahuas?

Those are the questions Elaine Ostrander wants to answer. She’s a biologist at the National Institutes of Health in Bethesda, Maryland. Scientists in her lab study the evolution of dogs. “We’re interested in what makes different kinds of dogs look so different,” she says.

Why do collies have smooth, silky hair? Why do poodles have cute curls? What gives a pooch spots, swirls, or stripes? And how did Great Danes get so big? They’re 40 times bigger than Chihuahuas.

Those are the questions Elaine Ostrander wants to answer. She’s a biologist. She works at the National Institutes of Health. It’s in Bethesda, Maryland. Scientists in her lab study the evolution of dogs. “We’re interested in what makes different kinds of dogs look so different,” she says.

To learn how various dog breeds came to be, Ostrander studies their DNA. This material is found inside cells, the microscopic units that make up an animal’s body. 

Parents pass down DNA to their offspring. Every living organism has slightly different DNA. These differences are what determine an animal’s traits, such as fur color, face shape, and body size.

Ostrander’s team recently analyzed the DNA of more than 1,300 dogs around the world (see Decoding Dogs, below). This enormous project took almost 20 years. The result is the most detailed doggy family tree ever made. It reveals how DNA mixed and matched over hundreds of years to create the huge variety of canine companions we see today.

Ostrander wants to learn why there are so many dog breeds. She studies their DNA. This material is found inside cells. They’re the microscopic units that make up an animal’s body. Parents pass down DNA to their children. Every living thing has slightly different DNA. These differences control an animal’s traits. Traits are things like fur color, face shape, and body size.

Ostrander’s team recently studied dog DNA. They collected it from more than 1,300 dogs (see Decoding Dogs, below) around the world. This huge project took almost 20 years. The result is doggy family tree. It’s the most detailed ever made. It shows how DNA mixed and matched. This took place over hundreds of years. That created the big variety of dogs today.

Dogs were first domesticated at least 15,000 years ago. They lived with humans before we started keeping chickens, cows, or cats. Scientists think dogs were first domesticated somewhere in Asia or Europe.

Domestic dogs are the descendants of wolves (see Fido’s Family Tree). In ancient times, wolves and humans hunted the same prey, such as wild horses. Some wolves started to feed on meat that people left behind. These animals learned to feel comfortable around people and became less aggressive.

Dogs are domesticated. People first tamed them at least 15,000 years ago. Dogs lived with humans before chickens, cows, or cats. Scientists think they know where dogs first began living with people. It was likely in Asia or Europe.

Domestic dogs are related to wolves (see Fido’s Family Tree). Wolves and humans hunted the same prey long ago. That included animals like wild horses. People left behind meat. Some wolves started to feed on it. These animals learned to relax around people. They became less aggressive.

“A dog is basically a wolf that has evolved to live off human trash,” says Adam Boyko. He’s a dog expert at Cornell University in Ithaca, New York. In fact, dogs and wolves are still the same species.

Eventually, people realized that they could pair up dog parents to pass down particular traits to their offspring. People started to breed dogs for qualities like size, speed, or intelligence.

Tall, lean dogs became racing breeds like greyhounds. Dogs with fierce barks and big bodies were bred into guard dogs like mastiffs.

“A dog is basically a wolf that has evolved to live off human trash,” says Adam Boyko. He’s a dog expert. He works at Cornell University. It’s in Ithaca, New York. In fact, dogs and wolves are still the same species. 

People eventually learned they could pair up dog parents. The dogs could pass down specific traits to their pups. People started to breed dogs for certain traits. They included things like size, speed, or intelligence.

Some dogs were tall and lean. They became racing breeds like greyhounds. Some dogs had fierce barks and big bodies. They became guard dogs like mastiffs. 

As humans moved around the world, they brought their dogs with them. In the Arctic, sled dogs pulled people and their belongings across the snow. In Mexico, people used hairless lapdogs as heating pads to soothe aches and pains. Native Americans in the Pacific Northwest even kept a longhaired breed called the woolly dog. People sheared the dogs like sheep and knitted their fur into blankets!

Today, dogs are the most popular pet in the world. There are 70 million of them in the U.S. alone. Breeders recognize more than 400 official breeds. So how are all these pups related?

Humans moved around the world. They brought their dogs with them. Sled dogs pulled people through the snow in the Arctic. They carried their belongings too. People kept hairless lapdogs in Mexico. They used them as heating pads. The dogs helped soothe aches and pains. Native Americans in the Pacific Northwest had a longhaired breed. They’re called the woolly dog. People sheared the dogs like sheep. They knitted their fur into blankets!

Today, dogs are the most popular pet in the world. There are 70 million of them in the U.S. alone. There are more than 400 official breeds. So how are all these pups related?

To find out, Ostrander’s team traveled to dog shows, Frisbee-catching contests, and other events. They collected thousands of samples of blood and saliva from 161 different breeds. Then they examined the samples in the lab.

First, the scientists used chemicals to extract DNA from the dogs’ cells. Next, they put the DNA in a machine that copies and analyzes it. The scientists knew that the more DNA two breeds share, the more closely they’re related.

Ostrander’s team traveled to dog shows to find out. They also went to Frisbee-catching contests and other events. They gathered thousands of samples of blood and saliva. The samples came from 161 different breeds. Then they looked at the samples in the lab. 

First, the scientists removed DNA from the dogs’ cells. Next they put the DNA in a machine. The machine copied and analyzed the DNA. The scientists knew closely related breeds would share more DNA.

Ostrander’s analysis turned up several surprises. For instance, you might think that pugs have few close relatives. With their unique scrunched faces and curly tails, they don’t look like many other dogs.

In fact, pugs share a remarkable amount of DNA with other small dogs across the globe, such as shih tzus and Pekingese. This suggests that pugs were one of the earliest miniature dog breeds, says Heidi Parker. She’s a scientist in Ostrander’s lab.

Ostrander’s study turned up several surprises. For instance, you might think that pugs have few close relatives. They don’t look like many other dogs. They have squished faces and curly tails.

But pugs share a lot of DNA with other small dogs around the world. They include shih tzus and Pekingese. Pugs were likely one of the earliest miniature dog breeds, says Heidi Parker. She’s a scientist in Ostrander’s lab.

The team also identified some breeds with ancient roots in North America. The first dogs in the Americas migrated from Asia around 10,000 years ago. But in the 1500s, European settlers brought new breeds. By modern times, people thought the old North American breeds had died out.

The new family tree tells a different tale. Ostrander and Parker discovered that seven breeds, including Chihuahuas and Mexican hairless dogs, share DNA that other dogs don’t have. They concluded that these breeds must have descended from ancient American pooches.

“That’s what makes this work really fun,” says Parker. “Every time we [study] a new breed, we find a new story.”

The team also found breeds with roots in North America. The first dogs there came from Asia. That happened around 10,000 years ago. But European settlers brought new breeds in the 1500s. People thought old North American breeds had died out by modern times. 

The new family tree tells a different tale. Ostrander and Parker found seven breeds that share DNA. They include Chihuahuas and Mexican hairless dogs. Their shared DNA isn’t found in any other dogs. The scientists believe it must have come from ancient American pooches.

“That’s what makes this work really fun,” says Parker. “Every time we study a new breed, we find a new story.”