There is nothing as romantic as two lovers sharing a kiss.But scientists have come up with an evolutionary explanation which perhaps threatens to kill the passion.
Academics
think that kissing helps partners share bacteria, shoring up their
immune systems and enabling them to better fight disease.
Academics think kissing helps partners share bacteria, shoring up their immune systems and enabling them to better fight disease
As many as 80 million bacteria are transferred during a ten-second kiss, according to Dutch biologists.
Sharing those germs means both partners are equipped to ward off the infections they might introduce to each other later on.
Humans
carry trillions of bacteria in the body, which together make up a
‘microbiota’ – a complex mix of bugs which play a crucial role in
digesting food and warding off infections.
Remco
Kort, from the Netherlands Organisation for Applied Scientific Research
- or TNO - said his team set out to discover the evolutionary reason
for kissing.
After testing 21 couples, they think kissing helps form a shared microbiota, a similar mix of bacteria living in the body.
He
said: ‘Intimate kissing involving full tongue contact and saliva
exchange appears to be a courtship behaviour unique to humans and is
common in over 90 per cent of known cultures.
‘Interestingly,
the current explanations for the function of intimate kissing in humans
include an important role for the microbiota present in the oral
cavity, although to our knowledge, the exact effects of intimate kissing
on the oral microbiota have never been studied.
As many as 80 million bacteria are transferred during a ten-second kiss, according to Dutch biologists
‘We
wanted to find out the extent to which partners share their oral
microbiota, and it turns out, the more a couple kiss, the more similar
they are.’
The
researchers, whose findings are published in the journal Microbiome,
found that couples who share nine intimate kisses a day had a very
similar microbiota, meaning they would be better prepared to deal with
similar infections and digest similar food.
Scientists
have long warned that modern obsession with hygiene and cleanliness has
driven a boom in allergies and health problems.
According
to the ‘hygiene hypothesis’, increasing prevalence of allergies such as
asthma are caused because we are not exposed to enough germs in our
daily life.
Professor
Graham Rook, an immunologist at University College London, has gone so
far as to say that picking food off the floor, buying a dog and
regularly kissing your relatives are some of the best ways to ward off
allergies.
Speaking
at Cheltenham Science Festival earlier this year, he advised that when a
baby spits out its dummy, a mother should lick it clean and put it back
in the infant’s mouth.
He said the problem is that the modern body is at a ‘constant state of alert’ because it is not used to living with germs.
‘When the immune system is not needed it should get turned off completely,’ he said.
‘What happens these days is that often it is on a constant state of alert and it is not turned off completely.
‘It
will do something completely pointless like attacking grass pollen
wafting past in the breeze, or attacking the neighbour’s cat when it
happens to walk past, then you are going to have allergic problems.’
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