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Something Wild: Smell that Olfactory

Courtesy Tony Alter via Flickr/Creative Commons.
It wasn't easy picking a topic this week.

We know…we’ve been remiss, and it’s time to talk about the elephant in the room. Something Wild, as you know, is a chance to take a closer look at the wildlife, ecosystems and marvelous phenomena you can find in and around New Hampshire. But over the years there is one species in New Hampshire that we haven’t spent much time examining. A species, I think that has been conspicuous in its absence. Humans.

So we’re grabbing the bull by the horns and digging in to a complex species that is an important part of the ecosystem. And we thought we’d start with a particular trait that’s been with us almost since the beginning: olfaction. The sense of smell among other sensory systems are relatively unchanged throughout mammalian history. As Nate Dominy, professor of anthropology and biological sciences at Dartmouth, says, “a lot of the traits we see in mammals are retention of those basic traits.”

Dominy suggested our olfactory sense was really important to our proto-mammalian ancestors. Picture it, it’s 70-80 million years ago, “dinosaurs and bird ancestors were dominating the diurnal landscape, so mammals are thought to be the subordinate creatures. There’s no way they could compete, so the only recourse was to be active at night.” And since there wasn’t a lot of light to see by, “they would have been highly dependent on olfaction for navigating through their environment, for detecting food resources” and just about everything else.

When the dinosaurs expired there was a void in the daylight hours. And without that competition early mammals became diurnal. Switching from the night shift to the day shift like that is bound to result in some changes in the organisms. And one of those changes was a shift of sensory emphasis. They began emphasizing their visual cortex, to better process all that light. And began de-emphasizing their olfactory bulb, where we process scents.

Some scientists think that there were other factors contributing to that de-emphasis. Kara Hoover, professor of Evolutionary Biology at University of Alaska specified migration. “Once we started moving out of Africa to new places in Eurasia, especially colder northern latitudes, the odor-scape shifts completely again to a very different sort of environment. Where it’s colder and drier as well. We don’t have as rich an odorscape at certain times of the year.”

These many factors contributed to the de-emphasis of the olfactory sense by early humans, and it kind of stopped developing. But then why is scent still such a powerful sense? Just a whiff of a particular scent can take you back in time to you grandmother’s kitchen, your first haircut or a bad night with tequila.

Hoover explained that’s probably because scent is processed in a different area of the brain from all of our other senses. “Olfaction gets process in multiple places in the hippocampus, where memory is located, and the amygdala where emotions are processed.” It’s easy to see how this would be an evolutionary advantage, “if you have a negative reaction to a new food or a bad food then it’s embedded in your memory, and that helps you avoid that food.”

All of this is relatively new science, as Dominy pointed out, much of what we know about olfaction has only come to light in the last 20-30 years.

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