Smell This: A Study in Scent

Sniff, sniff – there’s something in the air.

Is it fresh cut grass, the aroma of borscht cooking? Is it the stench of durian?

When compared with our other four senses, our sense of smell goes rather unnoticed.

Sight, sound, taste, touch – they all get plenty of play.

But smell…

Unless there’s a strong repulsion or attraction to an odor, this sense wafts under the radar.

And, yet, it’s one of our most powerful senses.

A Rose By Any Other Name…

Rockefeller University’s Andreas Keller conducted research on smell perception that demonstrated just how sensitive our sense of smell can be.

There’s a diverse complexity in scent that is unrivaled by sight and sound. The scent composition of a rose, alone, contains around 275 elements.

And humans can differentiate between trillions of these scents, according to Keller.

Keller’s study, published in Science Magazine in 2014, tested the capacity of humans to determine differences in various odor mixtures that had different shared components.

Their conclusion that humans can discriminate between upwards of a trillion odors far surpassed previous scientific literature, which determined 10,000 odors was our limit.

Comparably, we can only see somewhere between 2.3 to 7.5 million colors, and we can only hear 340,000 sounds.

As quoted in Keller’s abstract:

“[This research] demonstrates that the human olfactory system, with its hundreds of different olfactory receptors, far outperforms the other senses in the number of physically different stimuli it can discriminate.”

When it comes to the schnoz, the ear and eye can’t compare.

Evolution of Scent

Darwin knows the reason we can discriminate minute differences between odors: evolution.

What’s evolution got to do with it?

It turns out that smell is a handy tool for survival.

For instance, when we take week-old leftovers out of the fridge and give them a sniff, we can tell whether or not they’ve gone bad. If we crack that egg over the frying pan, and there’s a rancid odor, we know not to eat it.

So, if it’s a matter of life or death, the nose knows.

Another key factor in the study was that, when discerning scent, women regularly out-performed men. This may be because, throughout history, they most often prepared meals and had to know when food was rotten.

Animal Olfactory: How Do Humans Compare

After taking all this in, the human sense of smell may seem like a super power, but it falls way behind that of dogs and other animals.

Really, in the food chain of smell, we’d be on the bottom rung.

Think about it: this is the reason we use drug dogs at airports. Have you ever seen a customs officer sniff out a balloon of cocaine?

Regardless, our sense of smell is still incredibly sharp, and we’ll talk next week about how that sharpness impacts memory.

Coloring the World: The Evolution of Color Perception

What colors do you see here?

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What about here?

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Here?

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Here?

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It might surprise you to know that in Homer’s famed works, The Iliad and The Odyssey, he described the sea as wine-dark.

He described sheep’s wool as violet.

And the color of honey? Green.

All of this seems to imply that either the world’s color palette has changed…or, more likely, the human perception of color has.

Old Testament Eyesight

We assume that our world has and will always appear visually the same to everyone. In fact, that is not the case at all.

Guy Deutscher explains in his book, Looking Through the Language Glass, why the world looks different in other languages. 

Deutscher highlights philologist Lazarus Geiger’s 1867 discovery of strange color descriptions in old text.

Along with Homer’s descriptions, listed above, the Old Testament also describes faces that turn green with panic, red horses, and dove feathers in green gold.

These color descriptors are unusual today, and that may not be due to artistic license; rather, the evolution of eyesight may be at play here.

Evolution of Eyesight

Color perception and evolution walk hand-in-hand, according to one of the first research theories into what links the two.

As color perception became more important in developed civilizations (like the ancient Greeks), the human eye’s color sensitivity enhanced across generations.

Take blue, for example.

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The color blue was absent in early text (see the wine-colored sea above). Yet, the color red was everywhere, as distinguishing red was paramount to survival.

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Why?

Red=blood = danger.

Red appears in most old languages and has long appeared in garment dyes. Blue, on the other hand, has always been rare in nature and difficult to manufacture, thus our unnecessary sensitivity to it and its description.

Absence of Color

“The more delicate cones of the retina, which impart the higher color-sense, have probably developed gradually only during the last millennia.”

– biologist Ernst Haeckel, 1878

Darwin’s co-discoverer of natural selection, Alfred Russel Wallace, agreed with Haeckel. He said in 1877 that our “perception and appreciation of color” was a recent acquisition.

When researching language of color in traditional cultures – like that of the Klamath Indians in Oregon and the Nubians in Africa – scientists found similar color descriptors used as in old scriptural languages.

At the time, many in the scientific community assumed this similarity in language between old scriptural color descriptions and those used by what they called “primitive societies” was due to the assumed physical and intellectual inferiority of these groups (a popular belief at the time).

But they would soon discover they were very wrong to assume. Tune in next week to find out why.