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Did The Evolution of Dogs Coincide With Early Garbage Dumps?

MYLES GOUGH
18 FEB 2015

Man’s best friend may have evolved from wolves as recently as 15,000 years ago, around the time humans were establishing their first permanent settlements, new research suggests.

 

Using sophisticated 3D imaging techniques that can detect subtle differences in skull shape and size, an international research team has determined that two 30,000-year-old canine skulls, that had been previously identified as belonging to dogs, instead belonged to wolves.

The finding, published in Nature Scientific Reports, introduces new evidence into the long-standing and sometimes heated debate about whether modern dogs evolved in the late Palaeolithic Age, sometime between 20,000 and 30,000 years ago, when humans were still hunter-gatherers, or more recently, in the Neolithic Age, between 10,000 and 15,000 years ago, when humans had begun settling down in one place.

Abby Grace Drake, a biologist at Skidmore College in the US, who the led the study, told CBS news that, in addition to her finding, there is cultural and genetic evidence supporting the view that wolves transformed into domestic dogs during the Neolithic.

“The dog remains from the Neolithic are found buried with humans and adorned with ornaments such as necklaces of deer teeth,” Drake told CBS.

“Whether dogs were domesticated in the Palaeolithic or the Neolithic creates two different scenarios for how domestication may have taken place,” she explained. “In the Palaeolithic humans were hunter-gatherers. In the Neolithic is when we started to build permanent settlements that would have required 'dumps.' These piles of food and human waste would have attracted scavengers. Some scientists propose that wolves that scavenged at these dumps would have access to valuable food and those that could tolerate the presence of humans would be more successful.”

The two skulls that Drake and her team re-analysed were found in Russia and Belgium. They are roughly 32,000-years-old and were identified as belonging to dogs. However, in their paper, the authors say “new genetic studies contradict the identification of these specimens as dogs” and call into question the old method of measuring canine skulls - using only a caliper.

Drake told CBS that caliper measurements “do not distinguish between dogs and wolves and miss important aspects of the skull such as the angle of the orbits and angle of the muzzle.”

Her team’s 3D imaging technique examines 36 points on the skull, including the muzzle, teeth, and the braincase, and incorporates CT scans. Once her team analysed the two 'controversial' skulls, they compared their measurements to the skulls of more than 100 other dog and wolves. 

Their verdict was that the skulls belonged not to dogs, but to wolves.

“I was curious as to how these early fossils would compare,” Drake told CBS. “Would they appear as primitive dogs? Dog-wolf hybrids? I was surprised when I discovered they were shaped like the wolf skulls."

There has been some intense debate about when modern dogs first evolved. In 2013, a trio of papers were published all suggesting different timelines. One paper, which identified a gene in dogs that helps them break down starches – a gene that wolves don’t possess - suggested dogs might have evolved as recently as 10,000 years ago. Another said their evolution from wolves could have taken place 30,000 years ago – in southern China. 

This picture is made even murkier by the view held by several researchers that domestication may have occurred at different times in different places, and that ancestors of modern dogs may have continued inter-breeding with wolves, even after they buddied-up to early humans.

The findings of Drake's study have already been scrutinised by one researcher who is a proponent of the Palaeolithic timeline. Evolutionary geneticist Olaf Thalmann of the University of Turku in Finland wrote in an email to CBS that: “every new measurement of the remains reveals a different story” and that "the authors simply use a potential 'misclassification' of two samples to reject a hypothesis that has been supported by independent research before." 

It seems, until new evidence comes to light, the debate about when man's best friend actually evolved will continue to rage. 

Sources: CBSNature