快猫短视频

WOMEN seem to be drawn to men who smell like their father. In a test that
involved women sniffing unwashed T-shirts, they appeared to unwittingly prefer
the odour of men who have genes similar to their dad鈥檚.

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 among offspring, 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, which encode parts of the immune system. These genes are thought to be
closely linked to others that dictate our natural odour.

These findings come as a surprise, because female mice are known to sniff out
males with MHCs different from their own, preferring them to mates with a
similar genetic make-up. And women were thought to do the same, according to a
study in which women sniffed T-shirts that had been worn by men (New
快猫短视频, 6 May 1995, p 19). But the new study paints a more complicated
picture.

Martha McClintock, Carole Ober and a team at the University of Chicago
studied 49 women whose own and whose parents鈥� MHC genes were known. The women
sniffed T-shirts unrelated men had worn, as in the earlier study, 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.

Surprisingly, the women preferred the odours of men who had some MHC genes,
or alleles, in common with them. On average, the owner of a woman鈥檚 most
preferred odour shared 1.4 alleles with her, whereas the owner with the least
appealing odour shared 0.6. What鈥檚 more, the alleles that matched were those
that the women had inherited from their fathers.

That goes against the prevailing theory that outbreeding鈥攕eeking mates
who are genetically dissimilar to you鈥攊s always best. Going for a mate
with different immune system genes from your own should ensure that your
children have the biggest possible arsenal for attacking pathogens. Also, the
rarer their MHC, the less likely it is that pathogens will have evolved to
outsmart them.

But 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 proven to successfully fight disease. 鈥淭here鈥檚 an intermediate number of
matches that鈥檚 probably optimal,鈥� she says.

Wayne Potts of the University of Utah in Salt Lake City has a different
explanation. Although mice go for mates with different MHC genes, they prefer to
share a nest with mice with a similar MHC genetic make-up, probably to ensure
they are near their kin. Woman may be attracted to their father鈥檚 odour for a
similar reason鈥攕o they can home in on relatives.

Potts says that Ober鈥檚 own studies show women tend to marry MHC-dissimilar men
(快猫短视频, 10 February 2001, p 36).
And marriage may be a more reliable indicator than old T-shirts, he points out.