Symmetry, immunity and attraction

What links our likelihood to reject a tissue transplant and how attractive we find somebody's face? Can we sniff out a potential partner? Deborah Waller takes a look at the fascinating world of the compatibility gene.

  • Mandrill at San Diego Zoo

    Credit: Dirk via Wikimedia Commons

Getting brand spanking new popular science books through the post is a perk of my job. Since I’ve only been here a few weeks, the novelty has definitely not worn off yet but, even so, receiving a copy of a book on the subject of my Master’s thesis was particularly exciting.

Dan Davis’ new book ‘The Compatibility Gene’ is a fantastic overview of a fascinating area of research, spanning evolutionary psychology, immunology, and genetics. From how our bodies fight disease, what attracts us to other people, and how our cells define themselves as ‘us’, this set of genes reveals information about what makes us unique. The compatibility gene (known more formally as the major histocompatibility complex) is the most variable part of the human genome. While all humans share a similar set of 25,000 genes, this cluster is made up of 140 genes, some of which have thousands of known variations. That is a whole lot of diversity.

Their existence was first noticed because scientists were trying to work out why some transplanted skin cells in mice were rejected while others were accepted. It turned out that our compatibility gene works out what is ‘self’ and what is from outside so those that were too different from ‘self’ would always be rejected. Now, the immune function of half of the genes in this set is known and in fact, they are the most important influence on our susceptibility to a whole host of illnesses.

But it is not yet known how the compatibility gene may affect all sorts of things that make up who we are, from who we are attracted to, to how our brains are wired. Some research has looked at the likelihood of a successful pregnancy depending on the similarity of these genes in the two parents [1]. Others have used smelly T-shirts to determine whether we sniff out compatible partners [2]. Still others have looked at the compatibility genes of people we think look sexy.

So how can we ‘see’ these genes to figure out who we like the look of? One idea is that our compatibility genes, and therefore our natural immunity to illness, are reflected in the levels of symmetry in our faces and bodies.This is because symmetry should be a measure of developmental stability and if we have good immunity genes, we are likely to have a more stable development.

It is well-known that we find symmetrical people more attractive. High levels of symmetry are associated with beauty and health across different human cultures, and studies have found that symmetrical men have more sexual partners and are more likely to cheat on their partners [3]. Some research even suggests that women are more likely to orgasm when having sex with symmetrical men [4]. But is there an evolutionary advantage in finding symmetry attractive?

This is where my research came in. Instead of using humans, my subjects were monkeys. More particularly, monkeys’ faces (and yes, this does sound funny and it has been known to send interviewers into fits of laughter). During my Masters, I was trying to find out whether particular compatibility genes give rise to more symmetrical faces, allowing particularly disease-resistant individuals to show off their genetic advantage to potential partners.

  • Histology image of lung transplant rejection

    Lung transplant rejection

    Credit: Wikimedia Commons

  • Mandrill at San Diego Zoo

    Mandrill at San Diego Zoo: is he symmetrical enough to get a mate?

    Credit: Dirk via Wikimedia Commons

There was some evidence to suggest that symmetry was related to certain compatibility genes and, interestingly, the effect was more pronounced in males. This may be because testosterone is known to suppress the body’s immune response so having a naturally strong resistance to diseases is even more important [5].

The results were only preliminary and, although the role of these genes is well known in the immune system, scientists still argue over the what influence these genes have on other parts of our lives and bodies. With his research developing microscopes to be able to see immune cells’ interactions, Dan Davis may be able to shed more light on what compatibility genes could be responsible for. And how their brain cell-like communication could affect more than we ever imagined. 

Dan Davis will be speaking at the Royal Institution on Thursday 20th March at 7pm. You can read more about the research and his book, 'The Compatibility Gene: How Our Bodies Fight Disease, Attract Others, and Define Ourselves' on his blog posts on the Huffington Post and Oxford University Press website.

Notes

[1] Ober C, 1992.The maternal-fetal relationship in human pregnancy: an immunogenetic perspective. Experimental and Clinical Immunogenetics, 9(1), pp.1-14

[2] Wedekind, C.,Seebeck, T., Bettens, F. and Paepke, A.J., 1995. MHC-dependent mate preferences in humans. Proceedings of the Royal Society B: Biological Sciences, 260(1359), pp.245-9

[3] Thornhill, R., Gangestad, S., Miller, R., Scheyd, G., McCollough, J. and Franklin, M., 2003. Major histocompatibility complex genes, symmetry and body scent attractiveness in men and women. Behavioral Ecology, 14(5), pp.668-678.

[4] Thornhill, R., Gangestad, S.W. and Comer, R., 1995. Human female orgasm and mate fluctuating asymmetry. Animal Behaviour, 50, pp.1601-1615.

[5] Grossman, C.J., 1985. Interactions between the gonadal steroids and the immune system. Science, 227, pp.257-261.

The compatibility gene: Thursday 20th March, 7pm

Dan Davis' Book

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