Quote:
Originally Posted by Flyndaran
Even humans with close to half our mammalian scent genes broken or turned off permanently have over 1000 specific receptors.
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TLDR; While we may have "half" the number of receptors than a mouse or rat, this doesn't seem to have hurt us much. We may just have kept 'only the good ones' and dumped things that made the situation ambiguous, or were enabling pheremones.
Once they actually started
testing human capability (only done recently), they found that
untrained humans are actually better than mice and rats at discriminating between just about every random pair of scents they tried. They actually had trouble finding things that humans
can't distinguish, whereas this wasn't a problem with the animals.
The experimenters even got a human to follow a scent trail through the
air across a field as well as the baseline dog - the trick was finding a scent that humans are particularly sensitive to. They picked chocolate :)
The whole thing about humans have an abysmal sense of smell comes from a rather incoherent chain of "reasoning from random factoids" that got entrenched as "fact" before science really started looking at this seriously.
The initial claim was that we must not be
controlled by smell, as only a small percentage of our brains are dedicated to smell. That was a pretty legitimate idea.
Then the game of scientific "Telephone" began, and the next claim was that because a low percentage of our brain is dedicated to smell, we must be bad at it. No particular research backing this up, it was just stated. This was broadly accepted, probably in part because humans live with dogs, who are smelling rockstars.
Then the genetic assay was done and seen to confirm this "fact", and then nobody bothered to do any more research until recently because clearly this was a "done" field.