food and water in scarce environments.
Astonishingly, the human nose can detect 1 trillion odors,
including many we don’t even realize we are detecting. It’s well
known that women living together in dorm rooms are able to
synchronize their menstrual cycles; the reason is they are nasally
detecting each other’s pheromones. Women may have a keener sense
of smell than men, and it sharpens during pregnancy, when they must
be alert to subtle hazards. Diane Ackerman writes in A Natural
History of the Senses that mothers can identify their babies by scent
alone, but fathers can’t. My sense of smell is my sharpest sense, for
better or worse. My nose detects hazards before my husband’s, such
as something burning that is not supposed to be burning, and it gets
my heart beating very fast, a classic fear response.
We’ve all heard that horses and dogs can smell fear, but it turns
out that humans can too. To prove this, researchers collected
undershirts of men who went skydiving for the first time. They then
presented study subjects with either those shirts or ones worn by men
who did nothing scary. The researchers measured elevated stress
hormones only in the subjects who smelled the skydiver sweat. They
smelled the terror and then caught it too. Fear detection is a handy
skill in a social animal.
Sadly, though, our brilliant sense of smell may be on the wane.
Svante Pääbo is the Swedish paleogeneticist famous for sequencing
the genome of Neanderthals and discovering that they interbred with
early Asiatic humans (the result: all modern humans, except
Africans). From genetic evidence, he posits we are drastically losing
our sense of smell. We have a thousand genes involved in nasal
reception, but over half of them have become inactivated due to
mutations. In wild apes, only around 30 percent of the smell genes are
dysfunctional. Presumably, the mutations persist in humans because
losing some smell ability no longer affects our survival. We no longer
use our noses to find food, except perhaps Cinnabons in the airport. In