Human Journey

Dogs Can Sniff Out the Differences Between Identical Twins

Twins chow down at the Mule Skinner Saloon in Oxford; photo by Joel Sartore


Who is who in this picture?  Maybe you can’t tell the difference but your canine friend, Rover, might be able to help you out.  According to recent study conducted by scientists in the Czech Republic, some dogs are able to distinguish between identical twins even when a DNA test cannot.  Dogs in the experiment sniffed samples from sets of both identical and fraternal twins between the ages of 5 and 13 years old.  Samples from unrelated children were included as well.  In every trial, researchers found that the dogs could both match the twins’ scents and distinguish them from one another — indicating that even people with identical genes have their own unique scent.

Rover might need a little practice before performing this trick, however.  All the dogs used in the experiment were German Shepherds and highly trained.

The scientists have published the results of their study online in the journal PLos ONE.

For all the latest science news, check out our twice-weekly news rundown, Earth Current.

Alyson Foster works in the National Geographic Library where she purchases books for the Library’s collection and assists NG staff with finding research materials.
  • samgoldencoffee

    wow….things the four-legged friends can do.
    very amazing.

  • Warren Levine

    LOL! Obviously, if the one on the left has a burger with his mountain of waffle-fries, he’s gonna smell different than the one on the right who’s eating a fish sandwich with his (slightly larger) mountain of waffle-fries

  • Susan Pierce

    Did they try the same experiment with younger children? If so, How young?

  • Daphne Gagnon

    I have a blind dog and I am an Identical Twin. When both my sister and I walk into my appartement my dog sniffs my sister and waggs her tail, then she sniffs me and goes nuts, jumping and vocalizing. So yes she can tell differences between us

  • Abhishek kumar

    i love food

  • Beverley Sutton

    @Warren … the photograph above is merely an illustration showing identical twins … and has nothing at all to do with the experiment which the article reports was done in the Czech Republic and not at “at the Mule Skinner Saloon in Oxford.”

    I haven’t read the study, but one assumes that the researchers corrected for obvious scent differences such as those caused by diet, personal and laundry soaps … or they would not have been published.

  • Saqib Khan

    Even dogs are able to detect cancer long before it is confirmed by a laboratory. I read long time ago that a dog kept on licking a particular part on his master’s leg that made him curious and consulted his doctor. They found out through blood test that he was suffering from early stages of Melanoma.

  • Stephanie

    Not really a surprise, people all have their own scents, regardless of how much we cover it up with deodorant and perfume. It’s not an awful one, but you know how certain houses smell different and girls keep boyfriends’ sweaters because they smell like them? Same thing, it isn’t surprising that two people have different smells, regardless of genetic makeup.

  • Arbie

    I wonder…. has there been any case where a wife mistakenly took his bro-in law for her hubby ? If its ‘done’….wow….thats serious !

  • Shab

    Are you kidding? DNA test cannot?
    That is amazing that dogs can do that, but who says that DNA test cannot distinguish such a simple difference!

  • Red Twin

    Guess what? Anyone can tell the difference if they actually know the twins. My husband can hardly see the similarities between me and my identical twin.

  • […] Dogs Can Sniff Out the Differences Between Identical Twins Twins chow down at the Mule Skinner Saloon in Oxford; photo by Joel Sartore […]

  • James Smith

    The test is very unscientific. Differences in scent can be from many factors, diet, aftershave, degree of physical activity, type of clothes worn, aftershave, soap, other people in their normal proximity, many other factors.

    Until all variables are eliminated, this “experiment” means nothing.

  • Me

    Its not about what aftershave you wear or what you had for lunch. Dogs can smell internal disease. They can detect brain tumors. Their sense of smell goes deeper than skin level. Plus they can detect subtle changes in energy. Humans beings are electrochemical machines.when a DNA telld can’t detect these differences but a dog can, you have to look at the notion that its more than just smell.

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (

Social Media