Recent findings by a University of Massachusetts biologist have significantly altered previous understanding of the developmental rifts between the closely related dog and wolf species.

A study conducted by evolutionary biologist Kathryn Lord focused on what sets dogs and wolves apart genetically, according to a press release.

Dogs and wolves are given separate definitions even though they are very physically similar, and both are subspecies of the same taxonomy, Canis lupus. Wolves typically live in the wild, and it is rare that you would find one being kept as a pet. This is the opposite case for dogs, however, as they are much more apt to be animals bred for human companionship.

By comparing the behaviors of wolf and dog pups, in addition to recording their reactions to various stimuli, Lord confirmed that both species develop most of their sensory abilities such as sight, smell and hearing at around the same time, yet it is during the “critical period of socialization” that the two species’ behaviors diverge, according to the release.

According to Lord’s study, both dogs and wolves go through a month-long critical stage of social development, during which they both begin to explore their surroundings and new senses without fear, familiarizing themselves with their surroundings. At the closing of this “socialization window,” new stimuli are likely to elicit a fear response, the release reported, adding that Lord’s study shows that wolves begin this stage of socialization at two weeks of age; dogs do not begin this stage until they have aged at least four weeks.

The release said that though both dogs and wolves develop their sense of smell at two weeks, hearing at four weeks and vision by six weeks, it is due to this critical stage of socialization that essentially separates the two.

Another point discussed in the study is the correlation between the social development of the two species, including the difference in how long it takes for dogs and wolves to learn to walk. Wolf pups are walking on four legs by the time they are two weeks old, still blind and deaf and relying only on their sense of smell. For dogs, the ability to walk only comes after most of their sensory ability has developed. The critical stage of socialization comes concurrently with their ability to walk, according to the release.

“When wolf pups first start to hear, they are frightened of the new sounds initially, and when they first start to see they are also initially afraid of new visual stimuli. As each sense engages, wolf pups experience a new round of sensory shocks that dog puppies do not,” Lord said in the release. This shock for wolves, and the lack thereof for dogs, is what initially sends the two species on different developmental trajectories, ultimately allowing for dogs to have interspecies relationships with humans, according to the release.

Speaking with the genetic implications in mind, Lord said in the release that “the difference may not be in the gene itself, but in when the gene is turned on,” referring to the wolves’ socialization prior to total sensory development, which is innately what keeps them wild. Since dogs’ socialization period comes when they can see, smell and hear that with which they are familiarizing themselves, according to Lord’s research, this ultimately makes them friendlier.

In the course of Lord’s experiments she observed 43 dogs total from two different breeds, in addition to 11 wolf puppies from three different litters, the release said.

“It’s quite startling how different dogs and wolves are from each other at that early age, given how close they are genetically,” Lord said in the release.

George Felder can be reached at [email protected]