Rats can smell whether two people are related or not, according to new research. The discovery underlines the fact that a person’s natural smell can depend on their genes, and that odour similarities between related people are significant enough to be detected by the sensitive nose of a rat.
Erin Ables of Indiana University carried out the slightly bizarre experiment by recruiting groups of women, including pairs of relatives, and asking them to shower in non-scented soap, as well as avoiding smelly foods or cosmetics. She then presented smells to the rats – first from one woman and then another, either related or unrelated to the first. Rats spent longer sniffing the odours from unrelated women, and as rats spend longer investigating novel odours, this suggests that related women bear similar natural smells. The rats were even sensitive enough to spot the difference between a mother-daughter relationship and the more distant aunt-niece link.
It’s unclear whether people can consciously detect such differences, but it seems likely that we might appreciate them on some level. A person’s natural smell gives subtle clues about the genetics of their immune system, and people naturally tend to prefer the smells of people with different, and therefore complementary, immune genetic complexes to their own – a mechanism that might also help to avoid inbreeding. It’s also unclear whether the rats would succeed in the experiment if presented with odours from men – arguably the smellier members of the human race.