Posted by: inforodeo | August 13, 2008

Birth Control Pills Weakening The Human Race

The Pill may change women’s choice in men

By Roger Highfield, Science Editor

Last Updated: 12:01am BST 13/08/2008

The contraceptive pill changes a woman’s choice in men, a study suggests.
Scientists believe taking the pill changes the way a woman reacts to a man’s smell.
One consequence could be that they are more attracted to partners with whom it will be harder to conceive if they want children.
A man’s aroma can give a clue to his type of genes and ability to fight disease, although it is complicated by factors such as soap and aftershave.
Women subconsciously react to a man’s smell to pinpoint a partner with dissimilar genes to themselves. It is important to have a mixed immune system to combat different diseases.
But taking the pill could disrupt this natural ability, says a study at the University of Liverpool published in the Proceedings of the Royal Society B: Biological Sciences.
Disturbing a woman’s instinctive attraction to genetically different men could result in difficulties when trying to conceive, an increased risk of miscarriage and long intervals between pregnancies. Passing on a lack of diverse genes to a child could also weaken their immune system.
Called the Major Histocompatibility Complex (MHC), different MHC molecules fight different diseases, so it is important to have a mix of MHC types.
Earlier work has shown that, even though humans have a relatively poor sense of smell compared with other creatures, women tend to identify partners with suitable MHC molecules: preferring males with the correct mix of immune genes critical for the survival of future offspring and to curb inbreeding, which is harmful.
The research team analysed how the contraceptive pill affects odour preferences. One hundred women were asked to indicate their preferences on six male body odour samples, drawn from 97 volunteer samples, before and after starting to take the contraceptive pill.
They did not find that women who were not on the pill were more attracted to men with a different MHC, showing that the extent to which preferences for genetically dissimilar odours varies from study to study.
But they did find that the pill made women more likely to be attracted to a man with a similar immune makeup.
Dr Craig Roberts, who carried out the work in collaboration with the University of Newcastle, said the effect was robust: “The results showed that the preferences of women who began using the contraceptive pill shifted towards men with genetically similar odours.
“Not only could MHC-similarity in couples lead to fertility problems but it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill, as odour perception plays a significant role in maintaining attraction to partners.”
As for evidence that a weakening of relationships had occurred as a result of the introduction of the contraceptive pill, he said: “Divorce rates were certainly lower before and up to the mid-60s when pill use became commonplace, but as you can imagine, there are plenty of alternative explanations for increasing divorce rates since then. A definitive study has yet to be done (I’m seeking funding for this).”
However, he added that a small study by another team of couples, around 60, in those who were more MHC-similar, “women were more likely to report having had affairs and reported lower sexual satisfaction with their current partner.”
And another study found that couples who seek help from fertility clinics tend to have more similar MHC genes than the general population.

very, very interesting. 
i suppose this whole smell thing is why i think my little sisters are all ugly, but other guys think they’re hot.


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