A couple sits at a table and flirt in a restaurant

Sexual attraction

If a species is to survive, males and females must meet and mate. What attracts us to someone – looks, physique… or even smell?

When it comes to first appearances, symmetrical faces and more ‘average’ faces – faces digitally combined from pictures of lots of different ones – appear to be judged more attractive.

In general men seem to be attracted to feminine rather than masculine female faces, while women may be influenced by their hormonal cycles, preferring more masculine-looking males when they are ovulating and more feminine-looking males at other times.

There is also a theory that says the proportions of ‘beautiful’ faces conform to a similar ratio. This ratio, the so-called Golden Ratio, has been used throughout history in the design of temples and sculptures. But men may be influenced by another ratio too. A low waist-to-hip ratio (i.e. a curvaceous body) is apparently most attractive in women. This might have an evolutionary basis, with a low waist size indicating that a female is not pregnant, while hip size could indicate fertility and energy storage (as fat). A small waist relative to chest size may also be more attractive.

So what about smell? Mice seem to prefer to mate with partners that differ from themselves in a genetic region known as the major histocompatibility complex (MHC). This highly variable region is important in our response to pathogens (and it also underlies the tissue matching needed in organ transplantation). By sniffing a fellow animal’s urine, rodents can judge whether a potential mate has similar MHC genes or not. The mixing of MHC genes may give offspring a better chance of fighting off infections.

Some famous ‘sweaty T-shirt’ experiments in the 1990s hinted that women may also prefer the smell of men with dissimilar MHC molecules. However, scientists have not yet been able to establish how this works, if indeed it does.

It remains to be seen how these various cues, as well as non-physical factors like sense of humour, govern attraction. Other aspects such as the appearance of material wealth also seem to have a clear impact on mate choice. In the end it’s likely that a whole host of factors influence our choice of mate.

Lead image:

Peter Morgan/Flickr CC BY NC ND


About this resource

This resource was first published in ‘Sex and Gender’ in January 2006 and reviewed and updated in October 2014.

Genetics and genomics, Microbiology
Sex and Gender
Education levels:
16–19, Continuing professional development