Dogs First Drawn to Humans for Food (Surprise!)
Widespread dog domestication coincided with the emergence of agriculture (and the food humans grew), finds an analysis of dog genomes.
Ever feel tickled as a dog approached you -- tail wagging, friendly face -- only to realize he was after that half-sandwich you had stashed in your bag? It turns out that food may also have been the original lure as dogs first became domesticated.
A detailed analysis of the dog genome has linked widespread dog domestication with the emergence of agriculture. Dogs were likely attracted to humans -- and our food -- as opposed to humans bringing dogs to settlements.
The genetic clues, outlined in the latest issue of the journal Nature, reveal how dogs adapted to a starch-rich diet, possibly around 12,000 years ago.
"Our findings show that it was crucial to early dogs to be able to thrive on a diet rich in starch," lead author Erik Axelsson told Discovery News. "That indicates that dog domestication may be linked to the development of agriculture. It is possible that dogs may have been domesticated independently at locations where agriculture developed early, such as the Fertile Crescent and China."
Axelsson, who works in Uppsala University's Science for Life Laboratory, and his team made the determination after comparing DNA from 60 dogs representing 14 diverse breeds with DNA from 12 wolves of worldwide distribution.
While wolves have no genomic signature associated with starch consumption, dogs possess at least 10 genes that mutated to provide functional support for improved starch digestion. Wolves can digest starch, but the mutations allow dogs to do this much more efficiently.
"It is possible that waste dumps near early human settlements supplied early dogs with a substantial fraction of their nutritional needs," Axelsson explained. "If so, they would have been eating leftovers of the food we were eating. That food might have included roots, cereals and food made from cereals, such as bread and porridge, in addition to some meat and bone marrow from discarded bones."
Solidifying the link between humans and dogs, our species also looks to have evolved adaptations for a starchy diet at about the same time.
Dog DNA additionally reveals an early shift in brain function, likely tied to behavioral changes associated with living around humans. Since all dogs descend from one species, the grey wolf, (with some breeding with other closely related canines) it's possible that natural selection favored certain types of wolves.
"Being an efficient scavenger included being less shy so as to not waste energy on running away frequently," Axelsson said.
Natural selection therefore already started the process of separating wild wolves from their settlement-scavenging counterparts before direct human domestication of dogs began.
The precise moment when dogs first evolved from wolves remains in question, however.
Susan Crockford, a researcher at Pacific Identifications Inc. and author of the book "Rhythms of Life," believes that dogs were domesticated by at least 33,000 years ago, but these canines did not generate descendants that survived past the Ice Age.
She told Discovery News that the "right wolf/human conditions suitable for getting domestication started were present at least 33,000 years ago. However, such conditions would have had to be present continuously -- stable -- for many wolf generations, perhaps 20 over about 40 years for the domestication process to generate a true dog."
The 33,000-year date remains controversial, with some researchers saying that supposed dog remains dated to that time might just reflect natural variation in wolf morphology. Bones buried in Israel and dated to around 12,000 years ago "are generally considered reliable as dog remains," Axelsson said.
He added that research on the dog genome could benefit human health in the future.
"Dogs and humans share the same environment," he explained. "We eat similar food and we get similar diseases. This, together with our finding that humans and dogs have adapted to a similar environment, makes the dog an excellent model for understanding the genetic causes of human diseases."
What's not to love? Dogs likely approached humans some 12,000 years ago for our food.
Detroit: The City of Roaming Dogs
May 1, 2012 -
Roaming dogs have been a part of the city of Detroit for a long time. It's estimated that the city has the most homeless dogs in the nation at anywhere from 30,000 to 50,000. The city, the poorest major city in the country, has a hard time controlling the issue. Many residents find that they can no longer pay to feed their dogs and just let them loose on the streets. A recent Rolling Stone article chronicled the issue in detail, along with the man who is on a mission to help the dogs and help his city. Photo: A pack of stray dogs located on Detroit's Westside.
The Rapper and the Dogs Rapper Daniel "Hush" Carlisle grew up seeing stray dogs roaming the streets of his city. In 2010, Carlisle uploaded a video to YouTube about the stray dog problem in Detroit. It quickly gained a lot of attention. The video came after the city failed to give Discovery Channel the rights to film a show about Detroit's stray dog situation, for which Carlisle was a location scout. Since then, Carlisle, along with filmmaker Monica Martino, says the city has been supportive of the group they founded, Detroit Dog Rescue. Photo: Detroit Dog Rescue co-founder Daniel "Hush" Carlisle taking possession of an owner surrender dog in Detroit. The dog was later adopted out to a family outside of Michigan.
Finding Homes Along with three other volunteers, Carisle and his team drive around the streets of the city fielding tips and looking for stray dogs who need help and who they can rescue. "About 80 percent of all the dogs we find have been rescued," Carlisle said. Carlisle's mission is to start the first no-kill shelter in the city. Photo: DDR field agent Shance Carlisle examining a mixed breed pit bull. The dog belonged to a family who lost their home to foreclosure on the Eastside of Detroit. The dog was killed a week later in a dog fight.
Cash Finds a Home DDR supporter Christopher Altman with a boxer left abandoned in a home located on the Eastside of Detroit, after the owner passed away. The dog was left in the basement for eight months and fed occasionally by the owner’s son. This boxer was adopted to a family in Monroe, Mich. The family gave him the name Cash.
Honey Gets a Groom and a New Owner Honey, a Chow/Terrier mix, was abandoned by her owner on the east side of Detroit. She was found tied up to an awning. Here , Honey is getting her first grooming. She was adopted by her groomer and now lives in Utica, Mich.
Chained Up DDR responded to a stray dog in the neighborhood. This American pit bull mix on the east side of Detroit was found with a double chain on its neck. The dog's owner eventually claimed the dog.
The City's Bravest Help Out a Stray This Pit bull/hound mix, found resting on a bed in an abandoned industrial area on the Eastside of Detroit, was being fed by Detroit firefighters whose department was nearby.
Creating Trust DDR field agent Patrick Ward gains the trust of a pit bull stray on Detroit’s Southwest side. The dog was taken in and fostered by Animal Welfare Society.
Joany Detroit Dog Rescue field agent Shance Carlisle rescues an American pit bull mix dog left abandoned on the Eastside of Detroit. After being treated for having a severe case of the mange, "Joany" was adopted out
"Completely Wild" "A lot of these dogs are just completely wild," Carlisle said. "And they are hard to rehabilitate because they have been on the streets their whole life and have never had to deal with people or owners." His passion for his city and for the dogs is what motivates Carlisle. He has made himself known to the community and gets calls regularly from people about tips, stray dog sightings and he even from owners who can't afford their dogs anymore. "I talk to everyone from postal carriers to drug dealers," he said. "I do it because I want to help these animals and these people and my city." Photo: A pack of stray dogs located on Detroit’s Eastside in an abandoned industrial park.
The Stray Chow A recent article in Rolling Stone has helped give Detroit Dog Rescue some attention, along with some funding. Carlisle hopes that the momentum can keep going and that he can create a no-kill shelter. Photo: A Chow stray on Detroit's Eastside. This dog eluded DDR field agents and was not rescued at the time of this photograph.
Adopt Yogi This is one of the dogs available for adoption via DDR's website. Yogi is a 9-week-old Terrier mix who is ready to come home with you.
Joey This is Yogi's brother Joey, who is also up for adoption. Follow Detroit Dog Rescue on Facebook and on their site here.
PHOTOS: Record-Breaking Dogs