What are genes known as in pairs

Choice of partner: influenced by the smell of the genes?

Always follow your nose: Allegedly, we can smell which partner is a particularly good genetic match for us - but does this actually influence the choice of partner? Genome analyzes now confirm that people prefer genetically dissimilar partners - but not always and everywhere. Because a surprising exception reveals: the influence of smell attractiveness seems to depend on the socio-cultural context.

When choosing a partner, the nose plays an important role: Many vertebrates can tell from the scent whether their counterpart is genetically similar. If two individuals with very different genes mate, this is an advantage for the offspring. This applies in particular to the immune system and above all to the so-called MHC complex.

This protein complex is essential for recognizing pathogens. A large variety of different MHC molecules guarantees that the body's own defenses can fight as many different pathogens as possible. In order to increase the resilience of their offspring, many animals therefore prefer partners whose MHC genes are clearly different from their own - a trait that they can smell.

Search for evidence in the genome

But do humans also perceive the typical fragrance signature of the immune system and does this influence their choice of partner? “What is known from the animal kingdom is controversial in relation to humans,” explain Claire Dandine-Roulland from the Université Paris Diderot and her colleagues. While some studies confirm a preference for partners with different MHC genes, others come to the opposite conclusion or cannot identify any trend at all.

The researchers around Dandine-Roulland have now made another attempt to clarify the debate about the smell of genes. To do this, they used the possibilities of modern genome analysis and looked for answers in the genome of 883 married couples. The genetic data came from subjects from Belgium, Germany, the Netherlands, Great Britain, Spain and Israel.

Tendency to dissimilarity

For their analysis, the scientists examined how similar the MHC genes were in the pairs. Were they more similar or dissimilar in their immune genes than two randomly thrown together male and female couples?

The result: In spouses from Europe, the research team actually found a tendency towards MHC dissimilarity - this effect was particularly pronounced in Dutch couples. The immune genes of these pairs were significantly different than those of the randomly generated control pairs. In addition, it was shown that the MHC genes in them differed particularly strongly from one another compared to other sections of the genome.

Exception Israel

However, the finding was completely different in the Israeli sample. Here Dandine-Roulland and her colleagues could not determine any MHC-dependent preference. In their opinion, this suggests that people can be guided by the scent of the immune system when choosing a partner. How much they can be influenced by it, however, also seems to depend on the socio-cultural context.

Certain social customs in some countries could restrict the choice of partner and lead to the fact that love seekers do not only trust their noses. In Israel, for example, it is more common than here to choose a partner with a similar social background - for example in terms of ethnicity or religion. Weddings among cousins ​​are also relatively widespread in this culture. Such factors could trump the role of the immune genes, as the researchers explain. (Proceedings of the Royal Society B, 2019; doi: 10.1098 / rspb.2018.2664)

Source: Royal Society

20th March 2019

- Daniela Albat