GeneBites

Long before dogs became part of our families, they were wild wolves. A small change in their DNA may have helped them take the first step toward friendship with humans.

Image from iStock.

I truly wish I could talk to my dog. Though in some ways, I already do.

Dogs do pick up on the meaning of certain human words – commands like “sit” and “down”, or more exciting ones like “walk” and “treat” (my dog’s personal favorites). They may not reply in sentences – unless you count “Woof!” – but they have their own way of talking back. A wagging tail says “Yes!” A head tilt says “Wait…tell me more.”

Let’s take a look into what genetics and evolution say about the silent understanding between us and our pups.

A recent study looked into a tiny piece of DNA that could help explain how dogs and humans can be so sociable, without ever sharing a common language. This tiny piece of DNA is called a transposable element (TE). Unlike the parts of our DNA that code for proteins to tell our cells what to do, TEs act more like a backstage crew in a play. They don’t perform on stage themselves, but they control when and how the main actors (genes) make their appearance.

Researchers found a special piece of “jumping DNA” inside a gene called GTF2I, which is linked to social behavior and communication. In wolves, this DNA piece helps the gene bend into a loop as the DNA folds up inside the cell. Scientists call this folding pattern chromatin architecture. The loop acts like a docking station where proteins can attach and switch genes on or off. Interestingly, most dogs don’t have this DNA piece, so their GTF2I gene folds differently, without that loop or the protein docking spots it creates. Without the ability to switch these genes on and off, most dogs show altered patterns of social behavior and communication, becoming more naturally social and trusting, compared to their wolf ancestors.

Interestingly, there’s a human parallel. Losing one copy of the GTF2I gene is linked to Williams syndrome, a rare genetic condition with a hallmark trait being extreme friendliness and sociability. The researchers propose that the missing TE in GTF2I in domesticated dogs creates a canine version of this hypersociability.

Over time, early humans likely preferred wolves that were less aggressive and rather more trusting, friendly, and attuned to our cues. Therefore, wolves that demonstrated these traits, presumably lacking the TE, would have been more successful living alongside humans and passed their traits on. Generation after generation, this gentle social bias created our lovable, 4-legged friends.

It’s worth noting that historically, genetics research focused mostly on the parts of DNA that code for proteins, the exome. For context, the human exome is only estimated to be about 1-2% of the genome, all of our DNA. All of this other DNA, including things like transposable elements, were dismissed as “junk”. But studies like this one demonstrate that the so-called “junk” can be powerful and influential. If just one small TE can shape a species’ personality and success at domestication, imagine what else is occurring in that other 98% of our DNA. 

As much as I sometimes wish I could speak to my dog, it’s still amazing the ways we can silently communicate. We have transposable elements to partly thank for the wags, nudges, and puppy dog eyes. Try reading this article aloud to your dog. They won’t answer in words – and honestly, that might be for the best – but you might just get a tail wag in reply.

Edited by JP Flores & Jayati Sharma