PH
Identical twins can be extremely difficult for humans to distinguish visually.
Dogs trained for scent identification have demonstrated an ability to discriminate between odor samples from identical twins under controlled conditions.
Environmental factors can influence an individual's odor even when genetics are extremely similar.
Dogs therefore aren't simply recognizing the genetic similarities that make twins look alike to us.
To an excellent canine nose, two nearly identical humans can still carry distinguishable chemical signatures.
© Czech University of Life Sciences Prague