Man and his best friend may not have been so chummy 30,000 years ago.
Turns out the genetic evidence used to suggest the domestication of dogs during the Paleolithic era isn’t as reliable as once thought. And a pair of researchers — including an assistant professor of biology at Skidmore College — believe they have compelling data to prove it.
Abby Grace Drake of Skidmore and Michael Coquerelle of King Juan Carlos University in Spain used three-dimensional mapping to measure slight differences between Paleolithic-era fossils found in Europe and ones belonging to domesticated dogs. The slight differences in measurements between the skull samples strongly suggest the fossils — once thought to be dogs and offered as sound proof of the species’ domestication — actually belong to wild wolves.
“I was really surprised actually,” Drake said after their findings were published Thursday. “We checked and double checked and rechecked.”
Though the exact date of the domestication has been widely disputed over the years, testing on fossils unearthed in Belgium and Russia seemed to offer solid proof that the domesticated dog existed as early as 30,000 years ago. But Drake said the scientists making that judgment based their assessment on measurements taken with calipers.
Using such a tool wouldn’t have allowed the researchers to see the slight differences between the wolf and dog skulls, Drake said. Using computerized tomography, however, allows a more thorough mapping of the skull, which then identifies inconsistencies between the fossil finds and other early dog remains.
“The difference between a German shepherd skull and a wolf skull is subtle,” she said. “You need to measure it in 3D to reliably tell which is which and the same is true for these fossils.”
Drake and Coquerelle were able to obtain 3D images from finds in the Goyet Cave in Belgium and the Eliseevichi Cave in Russia. A point-by-point analysis showed differences in bone angles — particularly around the eye sockets, or obits — that make them inconsistent with measurements known to be taken from dogs.
“The difference between a wolf and a dog is largely about the angle of the orbits,” Coquerelle said. “In dogs, the eyes are oriented forward, and a pronounced angle, called the stop, exists between the forehead and the muzzle. We could tell that the Paleolithic fossils do not have this feature and are clearly wolves.”
Also adding doubt is that Paleolithic man left no visual evidence of a relationship with dogs or an attempt to domesticate wolves. Drake said cave paintings are devoid of canines, suggesting the hunter-gatherers didn’t find them very important at the time.
“As we see today, people love to take pictures of their pets,” she said. “Here, there’s not a lot of pictures around showing this close association.”
More likely, Drake said man and dog began building their enduring friendship during Neolithic era, when humans began to form permanent settlements and take up farming. That could mean their relationship started only 10,000 to 15,000 years ago, not 30,000.
If so, Drake said the domestication of dogs was likely a result of them scavenging through the rubbish cast aside by the earliest human settlements. As wolves came in closer contact with humans, they became increasingly tame, she suggests.
“We had to have a dump nearby once that environment was created,” she said. “The wolves would come in to scavenge and then they tamed themselves, essentially.”
Their findings were published in Scientific Reports, an online, open-access journal from Nature Publishing Group. Drake said the reception has been positive from the scientific community, which has long debated the evolution of the human-canine relationship.
“This changes that origin story, which is really fascinating,” she said.