This is pretty neat.
Police dogs can distinguish identical twins
In twelve trials per dog, none of them ever identified the wrong twin as a match, … even though the children lived in the same home, ate the same food, and had identical DNA. No word yet on whether these dogs will be getting their own CSI spinoff.
What is it that dogs use to tell us apart? Why would our scent be different from that of someone with the same DNA raised in the same environment? Is it nature, or nurture? Or something else entirely?