In an award-winning paper, Kohl, et al (2001) observed that humans are relatively much smellier than other primates, an observation that might seem counter-intuitive until one compares our hygiene maintenance requirements with those of other primates. Why this is indeed the case, the authors noted, was unclear.
Yet educated guesses about reasons for our smelliness are well within reach; when we look at what makes human responses to putative pheromones remarkable and relatively unique. At first, with the discovery of the active VNO in humans, almost nothing seemed unique. But the human VNO is a fraction of the relative size of the same organ in other mammals. And thus far we can\'t account for much, if any, everyday sexual behavior by accounting for changes in VNO output.
Participants in the ongoing controversial debate over the function of the vomeronasal organ (VMO) have tended to assert mutually exclusive extremes: that either the VNO is a relic of a pre-homosapienic past (most researchers in the past); or, that not only is the VNO functional, it\'s evoked electrical activity is the only distinguishing characteristic of pheromones (or \"vomeropherins\": Berliner and the \"Erox gang\").
Both positions are untenable. The VNO is tiny in humans, but pumps out the micro-voltage. Androstadione (A1) and other chemicals reliably evoke vomeroactivity, as compared to androstenone, muscone, and other \"failed\" vomeropherin candidates. Such signals travel directly to the hypothalmus.
But the above and other putative pheromones do whatever they do to our sexual endocrinology (e.g., leutinizing hormone, testosterone) changes in sensual biology (e.g., skin conductivity) and behavior (e.g., judgements of attractiveness, more sexual partners), regardless of our recognition, thank you very much. At this relatively naive stage of enquiry, we ought to be humble enough to recognize such activity. Later we can stick on labels.
These putative pheromones take typical conscious (if we smell them) and unconscious (if we don\'t), olfactory pathways on their way to our psyche. They demand relatively more higher-order processing or cognition than do vomeropherins (at least one of which nonetheless still requires extra-vomero processing for its effect). Yet many of these chemicals have demonstrated more compelling sexual effects than \"true\" pheromones. Do we care? Yes!
Pragmatically speaking, then, there are two ways for a substance to act like a pheromone, via the VNO (or \"Va va va VNO!\")and via olfaction (stinkin\' thinkin?).
Humans very likely \"stink\" because they have to attract mates through two pheromonic channels (smell and VNO/hypothalmus communication), and not just the VNO.
Smell is richer, but much less sensitive than, vomeropheric response, and requires a \"stronger\" signal. This stink is relatively noxious to other animals who would be our predators ( -- were we not so unpalatable. Sorry, human ego! Ask not why the dog wanders out of the room.); or otherwise intrude on our survival space. With fewer such \"rapid auto-response\" survival concerns and demands, homosapiens is now freer to engage in cognition which is slow, unreliable, and \"high maintenance\" (we have to pay attention) for ensuring survival/reproductive fitness. But cognition is delightful for other uses. And it still works adequately in many or most survival or reproductive selectionsituations, and can even supplant \"lower brain\" survival responses. For example, if someone were unable to sense hunger normally, they might still look at a watch and know when it is time to eat. And perhaps it is more incredible than the \"moon-walk\" that Michael Jackson, the man with the disppearing nose, may have managed to produce offspring, and almost drop them on their heads, without any VNO!
We process conscious smells with the whole of our memories, present awareness, and imaginations (ask any perfumer.). We make cognitive decisions based on it\'s input. But at the most, our sexual behavior is ambiguously determined by it, added together with other nature-based determinants of our behavior.
Is this bimodality adaptive for humans? You bet! We have two phero-pathways we utilize for survival and making reproductive decisions. If environmental trends proceed as they are proceeding, of course, we will need both of them. This is perhaps both good, as our success at dominating and enslaving nature has evinced, and bad, as our success at dominating and enslaving nature has evinced.
Descartes credo should have read, then, \"I stink therefore I think!\" Thinking may be, in part, a by-product of our past victories over immediate, natural survival threats; and our odiferous bodies\' clearing out of space in which we might think. And with this greater reliance on higher order neural processing, comes greater freedom.
Did nature intend such human freedom? Or is freedom instead a merely accidental byproduct of smell, which is, in turn, merely a back up system for ensuring reproductive success?
Now that\'s something to stink about.
(c) DrSmellThis, 2003