Article: Beauty is in the nose of the beholder

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Interesting ...

 

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Chris (list mom)

 

http://www.alittleolfactory.com

 

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http://www.newscientist.com/article.ns?id=dn7668

 

Beauty is in the nose of the beholder

 

Facial attractiveness and smell give us contradictory messages about how

to select mates, new research has revealed.

 

Previous research on smell suggests that humans prefer odours from

potential partners who are genetically dis-similar. But new research in

which women rated the facial attractiveness of men suggests the exact

opposite. So sight and smell appear to be giving contradictory messages

about which partners to choose.

 

The new research investigated possible links between mate preference and

the major histocompatibility complex (MHC) - the huge molecule on cells,

unique to each individual, which helps our immune systems to distinguish

native from alien cells.

 

The underlying theory is that humans avoid the dangers of inbreeding,

and maximise the chances of having genetically fitter children, by

selecting partners who have a vastly different MHC from their own. That

way, there is more chance of one parent's genes compensating for faulty

genes in the other. But how the senses pick up subliminal cues about

someone else's MHC is still something of a mystery.

 

Most research so far has focused on smell, especially in rodents, and

has backed up this basic assumption. Male and female mice, for example,

usually select mates with different MHC, which they judge by smelling

each others' urine.

 

 

Subtle effects

 

 

Smell experiments in humans have broadly given the same message, showing

that body odour is more appealing in people with vastly differing MHC.

But new research in which women rated the attractiveness of men's faces

has bucked the trend, showing that women preferred faces of men with

similar MHC.

 

" It's a subtle effect, " says Craig Roberts of the University of

Liverpool, who led the team which made the discovery. " We're not saying

it's something that rules who we find attractive. "

 

Roberts and colleagues recruited 92 women and 75 men, and recorded

differences in their MHC by analysing DNA from blood samples. Then each

woman was asked to rate photographs of six men, three with similar and

three with different MHC.

 

The results showed that, visually, the women preferred men with similar

MHC. The preference applied both to long and short relationships, but

was strongest for potential long term relationships.

 

 

Cultural advantages

 

 

Although the results appear to contradict those applying to smell,

Roberts and his colleagues offer an explanation to resolve the paradox,

based on the notion that kith and kin - despite having similar MHC - can

offer cultural and social advantages in child rearing.

 

The team suggests that " filtering " for mates takes place at two levels -

the first based on facial likeness to select someone not too distantly

related, and the second based on smell, essentially to avoid

in-breeding.

 

" It is a plausible explanation, " says Claus Wedekind, now visiting

Harvard University in Cambridge, Massachusetts, and whose research

provides the strongest evidence that on smell alone, humans and mice

prefer mates with different MHC.

 

" It could be explained by a desire for cultural 'sameness', but you

could build up 20 or more equally plausible scenarios to explain it, " he

adds, citing evidence that, in general, Americans prefer to marry within

ethnic groups.

 

But even incorporating smell research, the picture remains unclear. A

study by Martha McClintock and colleagues at the University of Chicago,

US, showed that women preferred odours matching the MHC of their

fathers. And Wedekind showed that women taking contraceptive pills

switched to preferring odours of men with similar MHC, an effect also

seen in pregnant mice.

 

Journal reference: Biology Letters (DOI: 10.1098/rsbl.2005.0343)