Humans, like other animals, are able to discern the young from the old by smell alone, according to a study published yesterday (May 30) in PLoS ONE.

Body odor is thought to convey a number of social cues due to its complexity, including information that aids in selecting a suitable mate and recognizing kin. There is evidence that animals can differentiate age groups based on smell, and researchers at the Monell Chemical Senses Center in Philadelphia wanted to test if the same were true in humans.

The researchers used pads sewn into the underarm area of T-shirts to collect body odor from male and female donors who wore them to sleep for 5 consecutive nights.  After the donors, who constituted three age groups—young (20–30 years old), middle-aged (45–55 years olds), and elderly (75–95 years old)—handed in their T-shirts, young participants were asked to smell the shirts and assess the...

Participants, who were both male and female, were able to discriminate between the three donor categories, and contrary to the anecdotal perception of the “old-person” smell being highly unpleasant, found the smells from the old-age group to be less offensive than the other two.

“Being the very first study to assess the ability of human participants to determine age from body odors, we focused on a very narrow research question and much remains to be explored,” the authors wrote, such as the biological mechanisms that produce the different scents.

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