I wonder how much we've lost not developing our sense of smell.
And to answer your initial question: my mom, a human, can smell where we, her family, have walked, she can follow the trail of smell. And please, we don't stink Strangers - no. Now when I get older, sometimes I can smell things almost as well as she can. But I always was able to wake up at night from smell of fire, smoke (even neigbours smoking weed at night), burning rubber, electric insulation, etc. Then I run around sniffing to find the source. Proved useful, if not always saving lives, quite often saving some property. Or can smell a little mould on an apple in the trash, I mean, just walking by the kitchen. And sure I can smell where my kids have been and what they have done. No secret smoking or anything.