DNA analysis, radiocarbon dating, and advanced measurement techniques are helping scientists understand the origins of dogs and when they became close companions to humans.
According to National Geographic, the evolution of domestic dogs took place over a long period.
Humans have been friends with dogs for tens of thousands of years. (Source: National Geographic).
When examining fossilized dog samples, researchers check characteristics such as size and arrangement of teeth, muzzle length, lower jaw structure, and skull shape. They compare these features with similar parts of modern dogs and wolves.
Ancient dog fossils display several traits such as short skulls and muzzles, crowded and smaller teeth (due to the short muzzle), and wide palates and skulls.
Moreover, scientists can employ advanced bone measurement techniques to analyze skull contours, making it easier to compare individual specimens.
It is not always easy to accurately determine what type of bones are being examined.
Some Ice Age wolf fossils have been classified as “primitive dogs,” indicating they were in an early transitional phase of development: neither fully wolf nor fully domesticated dog, but “somewhere in between [the two species].”
These fossils of “primitive dogs” resemble wolf-dog hybrids – the earliest ancestors of domestic dogs.
The oldest of these fossils – a large skull – was excavated in a cave in Goyet (Belgium) in the 1860s. Radiocarbon dating indicates that this ancient fossil is nearly 36,000 years old.
Belonging to a Paleolithic dog species, the Goyet dog skull resembles prehistoric dogs more than modern wolves. Radiocarbon dating and anatomical analysis of another fossilized skull – discovered in a cave in the Altai Mountains of Siberia in 1975 – suggest that this skull is approximately 33,000 years old.
Researchers concluded that the dog-like skull found in Siberia belonged to a dog in an early transitional stage of development.
Family Members
We can learn a lot about the relationship between ancient humans and dogs through the analysis of dog fossils.
For instance, the oldest known dog fossil, called the Bonn-Oberkassel dog, is believed to be just over 14,000 years old. The bones of this dog were discovered in 1914 in an ancient grave in Oberkassel (Germany), alongside the remains of a man and a woman.
In fact, Bonn-Oberkassel was a puppy around seven months old. A recent examination of this fossil concluded that the dog suffered from Canine Distemper – a viral infectious disease affecting dogs – and that humans had kept and cared for it prior to its death.
Gray wolf. (Source: National Geographic Kids).
This fossil also represents the oldest confirmed evidence of domestic dogs being buried alongside humans. Whether buried alone, with other dogs, or with humans, dog burials indicate a close bond between dogs and humans.
This suggests a “transition” of dogs from wild animals to “pets” within households.
In the 1970s, archaeologists excavated the bones of three domestic dogs at a site called Koster in the Illinois River Valley near the Illinois-Missouri border. The bone fragments were found in shallow pits, indicating they were intentionally buried.
Since no signs of tool marks were found on the bones (which would indicate they may have been killed by humans), it is believed that these dogs died of natural causes. Radiocarbon dating later revealed that the dog bones at Koster are approximately 10,000 years old.
The title of the oldest domestic dog fossil in North America belongs to a bone fragment dating back 10,150 years found in Alaska. Initially thought to be the remains of an ancient bear, DNA testing confirmed it belonged to a domestic dog.
Further analysis of this fossil suggests it is closely related to the ancestors of dogs that lived in Siberia around 23,000 years ago.
All of this indicates that Siberian hunters from the Ice Age may have domesticated dogs, and that humans – along with their canine companions – migrated from Siberia to North America approximately 4,000 years earlier than previously hypothesized, before the glaciers melted.
“Tracing the paths” of dog movement helps us better understand how humans migrated.
Looking further back, researchers analyzed the mitochondrial DNA of previously sequenced dogs and found that all ancient American dogs might share a common ancestor with dogs that lived in Siberia around 23,000 years ago.
Ancient dogs in North America largely disappeared after a few thousand years. This may be due to European settlers arriving in America with their own breeds of dogs, which quickly dominated the new lands.
Where Do Dogs Come From?
Many studies have focused on three main geographical areas – Asia, the Middle East, and Europe – as the origins of domesticated dogs. Some scientists believe that dogs may have been domesticated twice in different geographical regions, while others argue that dogs were domesticated only once.
Science has not yet accurately determined the origins of dogs, but each new study brings us a step closer to solving this mystery.
(Illustration: Alaska Wildlife Conservation Center).
Ancient dog-like fossils found in Belgium, Siberia, and the Czech Republic – all estimated to be between 36,000 and 33,000 years old. This indicates that wolves may have been domesticated in multiple locations.
Some DNA studies also suggest a “double lineage” of dogs. For instance, a large study in 2022 analyzing the DNA of ancient wolves provided evidence of possible dual domestication events in East Asia and the Middle East.
Two other studies published in 2021 also provided evidence regarding the “origins” of domestic dogs. One study indicated that dogs originated from Siberia around 23,000 years ago, while the other identified the extinct Japanese wolf as the closest relative to domestic dogs – suggesting that the ancestors of domestic dogs may have lived in East Asia.
Diving into DNA
Scientists have made significant strides in studying the evolutionary process of domestic dogs, but much of the research remains contradictory. We still do not know exactly when wolves became domestic dogs, nor is there a consensus on the origins of domestic dogs.
Mitochondrial DNA analysis, using a highly sensitive technique to examine a specific type of DNA found in ancient fossils, has opened up a new world of information for researchers trying to establish a timeline for the origins of modern dogs.
Since dogs and gray wolves share 99.9% of their DNA, researchers can analyze genetic variations. However, DNA analysis is not always straightforward, making it difficult to draw certain conclusions.
Scientists have not yet reached a consensus on the origins of domestic dogs. (Source: Guide Dogs Australia).
It is also challenging to use observable traits (such as body size, length and color of fur, head and leg shape) within individuals of the same species to compare modern dogs with their ancestors – a subspecies of gray wolves that remains unknown.
Although fossil evidence indicates that the domestication of dogs occurred around 14,000 years ago, DNA-based research often suggests that the “separation” between wolves and domestic dogs happened much earlier.
A 2022 DNA study analyzing 72 ancient wolf genomes spanning 100,000 years concluded that dogs likely emerged around 40,000 years ago, closely aligning with the timelines established by some earlier studies.
For example, in 2017, researchers analyzed genomes from three ancient dog fossils in Germany and Ireland. After comparing these ancient genomes with genetic data from over 5,000 modern dogs and wolves, the research team estimated that the “split” between dogs and wolves occurred between 37,000 and 41,000 years ago.
This study also identified that dog species divided into two populations between 17,000 and 24,000 years ago: Eastern breeds (ancestors of East Asian dog breeds) and Western breeds (which later became modern dog breeds in Europe, South Asia, Central Asia, and Africa).
Based on these timelines, they estimated that the process of dog domestication occurred approximately between 20,000 and 40,000 years ago.
Science and technology continue to provide new resources that assist researchers in their quest for answers. The more we explore, the more we will uncover about the origins of dogs.
