Women attracted to men who smell like dad
New Scientist, 21 January 2002
A T-shirt sniffing test has revealed that women unwittingly
prefer the smell of men who have similar genes to their dads. But this
is no Freudian Oedipal complex.
Instead, it appears to be a
tactic in a poorly understood evolutionary game, where the prize is
either greater resistance to disease, or an unconscious ability to spot
distant relatives in a sea of strangers.
The genes in question
form part of the major histocompatibility complex, or MHC, and encode
various components of the immune system. These genes are thought to be
tightly linked to others that dictate our natural odour.
on animals has shown that female mice sniff out males with different
MHCs to their own, prefering them to mates with a similar genetic make
up. Women were also thought to do the same, according to one study in
which women sniffed T-shirts worn for a couple of nights by men.
The same, but differentNow
a new study paints a more complicated picture. Martha McClintock,
Carole Ober and a team at the University of Chicago studied 49 women
whose MHC genes and parents' MHC genes were known. As in the earlier
T-shirt study, the women sniffed T-shirt odours, but this time they had
no idea what they were smelling. They were asked to say which odours
they would prefer if they had to smell them all the time.
the women preferred the odours of men who shared the same type of a few
MHC genes, or alleles, with themselves. The most appealing odour donors
shared 1.4 alleles on average, whereas the least appealing shared 0.6
alleles. What's more, these matching alleles were ones the women had
inherited from their fathers and not from their mothers.
goes against the prevailing theory that outbreeding is always best.
Going for a mate with different immune system genes to your own should
ensure that your children have the widest possible arsenal with which
to attack pathogens. Also, the rarer their MHC, the less likely it is
that evolving pathogens will be able to outsmart them.
McClintock thinks that interpretation is too narrow. Limited inbreeding
can work, as it may actually make sense to stick with combinations of
genes that are known to successfully fight disease. "There's an
intermediate number of matches that's probably optimal," she says.
Potts of the University of Utah in Salt Lake City has a different
explanation. Although mice prefer mates with different MHC genes, they
go for nest mates with a similar genetic make-up, probably to ensure
they are near their kin. Women may be attracted to their father's
odours for a similar reason - reflecting an ability to home in on
relatives using smell.
For instance, he says that Ober's own
studies show that women tend to marry MHC-dissimilar men (New
Scientist, 10 February 2001, p 36). "It is probably more reliable to
draw conclusions ... from marriage patterns," he comments, "than from
odour preference tests where boxes with odiferous, unknown contents are
Journal reference: Nature Genetics (DOI: 10.1038/ng830)