3-D analysis of dog fossils sheds light on domestication debate

September 20, 2017 by Lindsey Hadlock, Cornell University
3D plot of PC1–3 mandible shape variation. Black: dogs, dark grey: Alaskan wolves, light grey: European wolves, dark red: Ivolgin fossils, green: Ust’-Polui fossils, purple: Pleistocene Alaskan wolves, cyan: 1600CE fossil dogs, orange: unknown Alaskan fossil canids, pink: 1600CE fossil wolf. Credit: Scientific Reports (2017). DOI: 10.1038/s41598-017-10232-1

In an effort to settle the debate about the origin of dog domestication, a technique that uses 3-D scans of fossils is helping researchers determine the difference between dogs and wolves.

In the ongoing debate, one camp believes dogs were domesticated in the Paleolithic age (more than 17,000 years ago), when humans were hunter-gatherers. The other camp believes domestication occurred in the Neolithic age (17,000 to 7,000 years ago), when humans first established agriculture and civilizations.

Abby Grace Drake, a senior lecturer in the Department of Ecology and Evolutionary Biology (Cornell University), and her colleagues have been analyzing 3-D scans of ancient fossil canid mandibles to determine whether they belong to dogs or wolves. The answer, they find, is not so simple.

The researchers found that in the early stages of domestication, the skull changed shape but evolution of the mandible lagged behind and did not co-evolve with the skull. Their study is reported in the Aug. 25 issue of the journal Scientific Reports.

"A lot of the fossil evidence for the date of dog domestication is based on morphological [structural] analysis of mandibles," said Drake, the paper's first author. Robert Losey, an anthropologist at the University of Alberta, Canada, is a senior co-author of the paper. "Our study shows that when you measure modern dog mandibles and wolf mandibles using 3-D measurements you can distinguish them, and yet when we looked at these fossil mandibles, they don't look like dogs or wolves."

Wolves have fairly straight mandibles while dog mandibles are curved, structural features that become evident in a 3-D scan. In a proof of principle, when analyzing the 3-D structures of mandibles of modern dogs, Drake and colleagues correctly classified 99.5 percent of the samples as being dog or wolf.

However, 3-D analysis of fossil records from four ancient sites, two from Russia and two from Alaska, found that most of those fossil mandibles could not be classified as either dog or wolf, even though features in canid skulls from the same sites as well as other data proved that the samples were dog remains.

Other evidence also showed that these canids were domesticated: The remains were found within human dwellings, remains at both the Russian sites revealed butchery marks, indicating that they were eaten, and isotope analysis of canid and human remains from one of the sites - Ust'-Polui, in the Russian Arctic - showed canids and humans were both eating fish, and humans were feeding their canids.

Since mandibles do not appear to evolve as rapidly as the skull, the results show they are not reliable for identifying early dog fossils, Drake said.

Four of 26 fossil mandibles from Ust'-Polui, which was occupied from 250 B.C. to 150 B.C., were identified as dogs, while three of the mandibles from the site were identified as wolves.

At another site, Ivolgin, in southern Russia, occupied between 300 B.C. and 200 B.C., none of the 20 were identified as dogs, though 8 were identified as wolves. All of the skulls found at these sites, 12 from Ivolgin and five from Ust'-Polui, were clearly identified as dogs.

Canid fossils of wolves and dogs from the Alaskan sites from 1600 CE were used as controls and to compare genetic testing against the structural 3-D data.

2015 paper by Drake and Michael Coquerelle, an anthropologist at the University Rey Juan Carlos in Alcorcon, Spain, and a co-author on the current paper, used the 3-D technique to refute a claim that dogs existed 30,000 years ago. That claim was based on linear caliper measurements of skulls. Linear measurements are inaccurate because dog and wolf skull sizes overlap, Drake said. On the other hand, 3-D analysis of skulls uses landmarks across the to identify differences between dogs and in the angle of the muzzle, or snout, and in the angling of the eye orbits.

"The earliest I've seen in my analysis are from 7,000 to 9,000 years ago," Drake said.

Explore further: Science dates old dogs with new tricks

More information: Abby Grace Drake et al, Three-Dimensional Geometric Morphometric Analysis of Fossil Canid Mandibles and Skulls, Scientific Reports (2017). DOI: 10.1038/s41598-017-10232-1

Related Stories

Science dates old dogs with new tricks

February 5, 2015

Man's best friend has not been around for nearly as long as thought, according to a study Thursday that brings the emergence of modern dogs forward by some 15,000 years.

Study throws dog domestication theories to the wolves

July 18, 2017

From the tiny chihuahua to the massive Saint Bernard, domestic dogs today trace their roots to a single group of wolves that crossed the path of humans as long as 40,000 years ago, researchers said Tuesday.

Modern domestic dog has a single geographic origin

August 7, 2017

By analyzing the DNA of two prehistoric dogs from Germany, an international research team led by Krishna R. Veeramah, Ph.D., of Stony Brook University in the USA has determined that their genomes were the probable ancestors ...

Recommended for you

Meteorite source in asteroid belt not a single debris field

February 17, 2019

A new study published online in Meteoritics and Planetary Science finds that our most common meteorites, those known as L chondrites, come from at least two different debris fields in the asteroid belt. The belt contains ...

Diagnosing 'art acne' in Georgia O'Keeffe's paintings

February 17, 2019

Even Georgia O'Keeffe noticed the pin-sized blisters bubbling on the surface of her paintings. For decades, conservationists and scholars assumed these tiny protrusions were grains of sand, kicked up from the New Mexico desert ...

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.