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Photo: <a href="http://capl.washjeff.edu/2/l/4348.jpg">Washington & Jefferson College</a>, Creative Commons, some rights reserved
Photo: Washington & Jefferson College, Creative Commons, some rights reserved

Natural Selections: Sense of smell

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Humans aren't naturals at tracking smells like dogs, but they can, in fact, track by scent just like dogs. The main difference is humans get better with practice. Martha Foley and Dr. Curt Stager talk about people's sense of smell.

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MF: I read about this really cool thing in the newspaper and then I heard it on National Public Radio. It's about people smelling. People can track, by scent, like dogs can. I saw pictures of people, down on all fours, sniffing along a lawn.

CS: What could you get people to track? What kind of a smell would it have to be? Of course, chocolate!

MF: Chocolate (laughs)

CS: That's pretty neat. You always hear that we have this lousy sense of smell, and...

MF: And dogs are so good at it.

CS: Well, they are! If you want to have a hunt for a fugitive or something they call in the blood hounds, not the chocolate sniffers or something like that. So it looks like we're actually better at it if we practice, than we often think we are. We don't usually relate to smells that way. We smell the bakery walking by, but you don't have to use your scent talents to locate the bakery. You go by the sign. But it turns out that although the sensors in our nasal passages may not be as abundant or as sensitive as something like a dog would be, we have a larger brain that can process wimpy information and figure out how to use it.

MF: So we compensate for our bad noses with our big brains.

CS: Some of us would not be suprised to hear that this study was done on the west coast, in California, University of California at Berkeley; a very innovative, ground-breaking place.

MF: Thinking out of the box, out there.

CS: Yes. So they laid down a 30 foot trail of chocolate oil across a lawn and they got 32 Berkeley undergraduates and they blind folded them and had them follow the trail on their hands and knees. I don't know if they got a reward at the end or not.

MF: Well that's another thing. We're really not built to get down on the ground and stick our noses on scent like that. They did not look as comfortable doing this as my dog does. Not as fast, either.

CS: They were given 10 minutes and three chances to track the scent trail. About two thirds of them actually succeeded.

MF: Now you said practice a minute ago. Would it really be that you just need to pay attention more.

CS: I'm sure that's a lot of it. I also suspect maybe that your sense of smell may decline as you age. If you're a smoker you'll be burning it out a lot. They even said they could modify this experiment by blocking one nostril or using two of them. And it turned out to be significantly better if they had both nostrils going. 

MF: Do they know why?

CS: Umm...probably not, but the speculation is that you probably get a stereo effect kind of like having two eyes, binocular vision. If you have a stereo smell effect it might help you locate somehthing in space better. Snakes apparently do that with their split tongue. They wiggle it around and they can kind of tell which way the trail is trending by which fork its going on. So maybe it's something like that.

MF: So do you think we actually need a sense of smell. You know, we do have all these other senses; visual, chief among them, and hearing. Do you think it's just sort of a vestige?

CS: It's hard to say. The evolutionary ideas would say we share common ancesters with apes in Africa and most of those are forest dweller type things and they're probably not going to be following a whole lot of scent trails if you're up in the canopy. So, it's really hard to say and behavior doesn't fossilize very well, so maybe in the old days early humans used their sense of smell more for some things. But it's also a possibility that it's a leftover from ancestors way before anything that was like a human, that would have used it more. It hasn't gone away totally, yet.

MF: Just diminished a little.

CS: And we just use it to follow our nose to the bakery, or the chocolate trail.

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