More than man's best friend? Dogs and humans have undergone parallel genetic changes over the last 32,000 years, according to a new study.
The research found that dogs split from gray wolves about 32,000 years ago, and that since then, domestic dogs' brains and digestive organs have evolved in ways very similar to the brains and organs of humans.
The findings suggest a more ancient origin for dog domestication than previously thought. They also hint that a common environment drove both dog and human evolution for thousands of years, LiveScience reported.
"As domestication is often associated with large increases in population density and crowded living conditions, these 'unfavourable' environments might be the selective pressure that drove the rewiring of both species," the researchers wrote in the journal Nature Communications.
It isn't clear precisely when wolves were tamed and transformed into man's best friend, and the date has been hotly debated.
An ancient, dog-like skull uncovered in the Siberian Mountains suggested that the first dogs were domesticated around 33,000 years ago from gray wolves. But genetic analysis suggested dogs in China were domesticated only about 16,000 years ago.
Most researchers agree that by about 10,000 years ago, dogs were firmly ensconced in human society.
Guo-dong Wang, a genetics researcher at the Chinese Academy of Sciences, and his colleagues analysed the DNA of four gray wolves, three indigenous Chinese dogs and a German shepherd, a Belgian Malinois and a Tibetan mastiff.
The DNA suggested that the gray wolves split off from the indigenous dogs about 32,000 years ago, the researchers said.
"Chinese indigenous dogs might represent the missing link in dog domestication," the researchers wrote.
The team compared corresponding genes in dogs and humans and found both species underwent similar changes in genes responsible for digestion and metabolism, such as genes that code for cholesterol transport.
Those changes could be due to a dramatic change in the proportion of animal versus plant-based foods that occurred in both at around the same time, the researchers said.
The team also found co-evolution in several brain processes - for example, in genes that affect the processing of the brain chemical serotonin.
In humans, variations in these genes affect levels of aggression, the study found.
