Science / The smell teaches about suitable genes in the partner
By Nicholas Wade New York Times
Is the harmony between spouses not created out of a conscious thought but is it hidden in the genes? And is it possible for people to look for genetic compatibility with a partner through body odor?
Proof that women prefer the body odor of men who are genetically similar to them - but not too similar - was provided by a study conducted at the University of Chicago and published yesterday in the journal "Nature Genetics". Another interesting and far-reaching conclusion that emerges from the study - in which women smelled T-shirts worn by a man for two days - is that their preferences were based on the genetic compatibility of the man with each woman's genes from the father's side, not the genes from the mother's side.
Dr. Carol Ober and Dr. Martha McClinton, the authors of the study, believe that the method of matching genes may have been adopted by evolution because it helps prevent the risks of "consanguineous marriages" and marriages between people who are genetically very different. The genes in question produce proteins that identify the cells in the body as its own cells, for the functioning of the immune system. This group of genes is called MHC. In the experiment, men were told to avoid proximity to distracting smells such as the smell of spicy foods, deodorants, pets or sexual activity. The shirts they wore for two days were placed in boxes so the women could only smell them, but not see them.
The women were asked which box they would choose "if they had to smell it all the time". The women did not know what the purpose of the experiment was. When asked what the smell reminded them of, many of them answered "Kmart", apparently because of the boxes.
Humans inherit two complete sets of genes, one from each parent. The Chicago researchers compared the MHC components of the women with those of the men, whose scent they preferred, and found a match with genes from each woman's father, but not with those inherited from the mother.
The researchers said that the subjects preferred men with an average match to their MHC from the father's side, and showed no affection for high match gene carriers. This finding is consistent with the idea that it is better to avoid extreme situations of both closeness and genetic distance between spouses. In marriages between first degree relatives there is a risk that the offspring will inherit two defective versions of the same gene, one from each parent. And as for the partners who are genetically distant, this distance is indeed often considered healthy, but extreme situations of genetic variation between the partners may also be problematic, say geneticists.
According to Dr. Ober, the experiment does not prove that the choice of a partner is mediated by smell, because the women were not specifically asked about a partner. Even if body odor does affect the choice in small communities, it is not clear what effect MHC compatibility has in modern populations. And the candidate's education may overshadow the MHC signals, Dr. Ober said.
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