Before Spot reached Petco or the pound and went up for adoption, he had already taken quite a journey. New research places the evolutionary origins of the common dog as far away as Eastern Asia. A Cornell-based research group has taken a new approach to finding answers to difficult questions in canine genetics.
Current theories suggest that the domestication of dogs could have occurred for a range of reasons, including security and even as a source of food.
Popular theories exist that place the earliest domestication of the common dog in Eastern Asia. However, there is support for separate cases of domestication occurring worldwide in areas such as Europe.
While research is available on domesticated dogs and American Kennel Club breeds, scientific knowledge concerning stray dogs has traditionally been lacking. Human-driven artificial selection of dog species may have crippled the population of certain communities in events known to geneticists as population bottlenecks.
According to research associate Adam Boyko, biological statistics and computational biology, genes from these dogs are probably closer to those of the first domesticated dogs than those from modern dogs.
Researchers have gathered samples from stray dogs in more than 20 countries on six continents — all with the central goal of figuring out where dogs originated and why. The 1,317 samples are held in Cornell’s extensive veterinary DNA bank (among 6,300 other samples ranging from cats to cows).
According to Dr. Marta Castelhano, a veterinarian at Cornell’s College of Veterinary Medicine, many of the populations being examined have never been scientifically studied. “They are a footprint of human domestication,” she said.
The project started when Prof. Carlos Bustamante, biological statistics and computational biology, returned from a trip to Venezuela. He noticed how the stray dogs there appeared to be smaller. This observation sparked his interest in the genetic diversity expressed in stray dogs around the world.
While other studies have used mitochondrial DNA — a single genetic marker that can be biased by interbreeding — Boyko and his researchers are using hundreds of nuclear single-nucleotide-polymorphisms, which paint a more accurate picture. These are locations in the genome where there is known variation in different dogs, or between dogs and wolves. This reference point allows scientists to make insights into the individual’s genetic origins with less variability.
Castelhano has personally collected samples from Portugal. For her, there is a unique look to village dogs from different countries. “I would be able to recognize a Portuguese dog in comparison to any other,” she said.
These geographic distinctions occur, Boyko explained, because of the different environmental factors and selective conditions that produce characteristic physical features. Local customs and preferences may also affect physical features such as size.
Castelhano said that variation in size, color or behavior may indicate ancient mutations in the individual’s DNA. These mutations may appear today as diseases as a byproduct of intensive line breeding over many generations. “When selecting traits for breed characteristics, often disease genes accumulate along with the trait-specific genes,” she said.
One of the projects goals is to better understand the genetic mechanisms that cause disease in both wild and domesticated populations.
Apart from gathering DNA, the project team also provides veterinary care to all of their canine volunteers — from vaccine shots to medical attention, aiding both the dogs and the community.
For those curious about their Spot’s particular origin, Boyko’s team also accepts submissions of DNA samples for inclusion in the study.