You might not know this, but there are two distinct arguments about when dogs were domesticated. One group believes dogs were domesticated in the Paleolithic age (more than 17,000 years ago), and another believes dogs were domesticated much later, in the Neolithic age (17,000 to 7,000 years ago).
So, when exactly were dogs domesticated?
A team of researchers from Cornell University set out to find out which camp is right. They used 3-D scans of fossils to help determine the difference between wolves and dogs by studying ancient fossil canid mandibles (jaw bones) to determine if they were dogs or wolves.
How does mandible evolution distinguish a dog from a wolf? Wolves have fairly straight mandibles, while those of dogs are curved. These features become evident in 3-D scans.
The researchers, led by Abby Grace Drake, a senior lecturer in Cornell’s Department of Ecology and Evolutionary Biology, found that in the early stages of domestication, canids’ skulls changed shape, but the evolution of the mandible lagged behind.
“A lot of the fossil evidence for the date of dog domestication is based on morpohological [structural] analysis of mandibles,” said Drake, the paper’s first author. “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.”
Although the team could distinguish 99.5 percent of modern dogs’ mandibles from those of wolves, a lot of the fossil mandibles couldn’t be classified as either dog or wolf. However, other data proved that the fossils were dog remains.
Other evidence from two Russian sites showed that the canid remains were found with human dwellings, and there were marks that revealed butchery—meaning that the dogs were eaten. In addition, isotope analysis of canid and human remains at both sites indicates that canids and humans both ate fish, and that humans were feeding the canids.
Drake said that since mandibles don’t appear to evolve as rapidly as the skull, they are not reliable for identifying early dog fossils.
However, 3-D analysis of canid skulls uses landmarks across the skull—differences in the angle of the muzzle, snout, and eye orbits—provides more evidence of dogs’ domestication time.
“The earliest dogs I’ve seen in my analysis were from 7,000 to 9,000 years ago,” Drake said.