FORGET love horoscopes. If you want to know what the future holds for you and
a partner, sniff yourselves with an 鈥渆-nose鈥�.
Researchers in Germany have developed an electronic nose that can detect the
smells that mice use to choose mates with compatible genes. The device should
make it easier to test the controversial idea that people also rely on smells,
and that having the wrong ones may sometimes sow the seeds of divorce.
Rodents sniff their suitors to see whether they have the same major
histocompatibility complex genes as their own. MHC genes code for proteins in
the immune system, and the more diverse they are, the better your chances of
coping with new infections. So rats and mice, at least, follow their noses and
choose mates with different MHC genes, to endow their offspring with a varied
portfolio.
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Until now, researchers have not been able to directly measure differences in
smells associated with MHC genes. They have relied on rodents to do this for
them in behavioural experiments. But Hans-Georg Rammensee and his colleagues at
the University of T眉bingen have built an electronic nose that does the
job.
The e-nose has two components. The first contains a series of eight tiny
quartz crystals coated with different polymers. Odour molecules stick to
particular coatings, and just a few molecules will change the frequency at which
the crystal vibrates. The second part uses a series of semiconducting
metal-oxide gas sensors. Gases react with oxygen on the sensor surfaces and
change their conductivity. Both components are hooked up to a computer that can
recognise the patterns of each smell. 鈥淚t鈥檚 very sensitive鈥攊t can
distinguish different brands of coffee, for example,鈥� says Rammensee.
The e-nose has already singled out mice with different MHC genes by sniffing
their urine. And, as the team will report in Proceedings of the National Academy
of Sciences, it can also distinguish the smell of blood serum from people with
different MHC genes.
The jury is still out on whether MHC smells affect our choice of partners
(New Scientist, 10 February, p 36).
We probably mask MHC smells with
perfumes and deodorants. So a partner might only subconsciously register them
after a long exposure. Rather than being involved in the dating game, MHC
incompatibility may manifest itself in today鈥檚 high divorce rate.
Rammensee suggests that sociologists could use the e-nose to test this idea,
sniffing divorced couples to see if they have a higher incidence of MHC
incompatibility than those celebrating their silver wedding anniversary, for
example. 鈥淚t is speculation,鈥� he cautions. But if the idea is confirmed,
courting couples could one day be surreptitiously sniffing each other with
e-noses to find out if they make a good match.
