LONDON, Aug 22 (Reuters) - Family members tend not to like the way each other smell, researchers say, speculating that the unpleasant stink of your closest relatives may be one of nature's ways of discouraging incest.
In research described on Thursday in Britain's New Scientist magazine, a team at Wayne State University in Detroit recruited 25 families with children aged between six and 15, and gave them T-shirts to sleep in and odorless soap to wash with.
They were told to keep the T-shirts in plastic bags. They were later asked to sniff two T-shirts, one worn by a family member and another worn by a stranger.
The researchers first tested whether family members could recognize each other.
They found that mothers and fathers could usually tell when they were smelling their pre-adolescent children, with mothers being slightly better at it than dads, but they could not say which child was which.
Children younger than nine -- with the notable exception of sons who had been breastfed -- generally could not recognise their mothers, while older children could. All the children recognised their fathers.
Interestingly, whether or not they recognized which T-shirt belonged to a family member, volunteers usually said they far preferred the smell of the stranger's shirt.
Mothers particularly did not like the smell of their children, and children had a strong aversion to the smell of their fathers. Children of the same sex were not offended by each other's smell, but children of opposite sex were.
Researcher Tiffany Czilli said that she believed the dislike of each other's odors was part of nature's way of preventing incest, by making people less appealing to their closest relatives.
Other family issues could be at work too: the particular aversion that children have to the smell of dad could also be a sign of children trying to grow up and be independent.
But Dustin Penn of the University of Utah in Salt Lake City warned that asking people about their preferences could be unreliable.
"Just because people say they 'prefer' something doesn't mean they'll act in a preferential way," he said.