Cambridge University links love and smell in mandrills
A Cambridge University study reveals how mandrills find suitable partners
The theory that people can "sniff out" their partners appears to be confirmed by research from Cambridge University.
The study reveals how a breed of monkeys uses scent to avoid the potentially genetic disaster of mating with partners too closely related.
"You might have heard of studies which show that women prefer the odour of genetically different men," said Dr Leslie Knapp, who led the research.
"This kind of parallels that result," she explained.
Mandrills and Darwin
The study focused on mandrills - a very colourful monkey, which is found in Africa.
Males have a bright red nose and, until this study, it was thought they used their brilliantly coloured faces to advertise their compatibility with mates.
In fact it was Charles Darwin who originally suggested a link between colour and attractiveness in mandrills, as early as 1871.
"The red colour is still important because it attracts attention," said Dr Knapp. "And it tells the female something about the status of a male, whether he's dominant or subordinate.
Mandrills want more than good looks in the parent of their offspring
"But it seems that the odour is something that tells us some really important things about the genes of a mandrill."
Male and female mandrills have special glands on their chests that secrete a substance which they rub on various surfaces.
Researchers took swabs and hairs from male and female mandrills' sternal glands while they were undergoing routine veterinary inspections at the Centre International de Recherche Médicales in Franceville, Gabon.
They then studied the chemical compounds which make up the odour.
As a result they identified strong parallels between the specific chemical compounds that determine a mandrill's individual scent, and the pattern of their major histocompatibility complex (MHC) genes.
"These genes are involved with immune response," said Dr Knapp. "And so what a female mandrill - or in fact even a male mandrill - can detect from the odour of different potential partners is how genetically diverse they are.
"That might tell them something about their suitability as a mate for producing healthy offspring."
Scientists studied mandrills because they have sternal scent glands
Mandrills are a primate cousin of humans.
The findings of this study offer evidence that humans may possess a similar ability to identify partners with an appropriately different MHC genotype using their sense of smell.
"We all know that for humans it's pretty important to look at someone, and we are first visually attracted to them," said Dr Knapp. "But what this tells us is that, in addition to visual cues, there seems to be some scent cue that's important."
Other research has already revealed the importance of odour to members of the same family.
"There have been studies where women can identify the smell of their baby just by being give a piece of fabric with their baby's smell on, and comparing this with other women's babies," said Dr Knapp.
"So it seems we can recognise relatives with smell."
In each case in this study, individual mandrills appear to seek out partners with a different MHC pattern to their own on an 'opposites attract' basis, resulting in greater diversity of immune response in the offspring they produce.
Scientists had previously suggested that primates might be able to identify different MHC genotypes through smell, but no explicit link had been found until now.
Now they have also discovered the role played by mandrills' sternal glands.
"Scientists have long speculated about what their purpose might be. It would appear that we finally know," said Dr Knapp.
"To be able to answer a question that has been unsolved since Darwin's day feels quite amazing."
The findings are reported in the new issue of Proceedings of the Royal Society B. They were produced as part of an ongoing research project funded by the Leverhulme Trust and involving an international team of researchers led by Dr Knapp.
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