Thursday, June 17, 2010

Pretty faces are average faces: Genetic diversity and health

Many people think that the prettiest faces are those with very unique features. Generally that is not true. Pretty faces are average faces. And that is not only because they are symmetrical, even though symmetry is an attractive facial trait. Average faces are very attractive, which is counterintuitive but makes sense in light of evolution and genetics.

The faces in the figure below (click to enlarge) are from a presentation I gave at the University of Houston in 2008. The PowerPoint slides file for the presentation is available here. The photos were taken from the German web site Beautycheck.de. This site summarizes a lot of very interesting research on facial attractiveness.


The face on the right is a composite of the two faces on the left. It simulates what would happen if you were to morph the features of the two faces on the left into the face on the right. That is, the face on the right is the result of an “averaging” of the two faces on the left.

If you show these photos to a group of people, like I did during my presentation in Houston, most of the people in the group will say that the face on the right is the prettiest of the three. This happens even though most people will also say that each of the three faces is pretty, if shown each face separately from the others.

Why are average faces more beautiful?

The reason may be that we have brain algorithms that make us associate a sense of “beauty” with features that suggest an enhanced resistance to disease. This is an adaptation to the environments our ancestors faced in our evolutionary past, when disease would often lead to observable distortions of facial and body traits. Average faces are the result of increased genetic mixing, which leads to increased resistance to disease.

This interpretation is a variation of Langlois and Roggman’s “averageness hypothesis”, published in a widely cited 1990 article that appeared in the journal Psychological Science.

By the way, many people think that the main survival threats ancestral humans faced were large predators. I guess it is exciting to think that way; our warrior ancestors survived due to their ability to fight off predators! The reality is that, in our ancestral past, as today, the biggest killer of all by far was disease. The small organisms, the ones our ancestors couldn’t see, were the most deadly.

People from different populations, particularly those that have been subjected to different diseases, frequently carry genetic mutations that protect them from those diseases. Those are often carried as dominant alleles (i.e., variations of a gene). When two people with diverse genetic protections have children, the children inherit the protective mutations of both parents. The more genetic mixing, the more likely it is that multiple protective genetic mutations will be carried. The more genetic mixing, the higher is the "averageness" score of the face.

The opposite may happen when people who share many genes (e.g., cousins) have children. The term for this is inbreeding. Since alleles that code for diseases are often carried in recessive form, a child of closely related parents has a higher chance of having a combination of two recessive disease-promoting alleles. In this case, the child will be homozygous recessive for the disease, which will increase dramatically its chances of developing the disease.

In a nutshell: gene mixing = health; inbreeding = disease.

Finally, if you have some time, make sure to take a look at this page on the Virtual Miss Germany!

8 comments:

Kindke said...

Theres probably other programs out there but the game Dragon Age:Origins has an inbuilt face modifier where you can literally alter every imaginable feature of the face and skull very preciesly in real time.

After playing with it for sometime I found some generalisations that made female faces attractive to me, these were.....

1) Relatively wide jaw bone compared to width of bottom of chin
2) largish eyes
3) small rounded nose
4) relatively full figured lips.
5) slightly pronounced cheek bones
6) slightly convex brow
7) straight and vivid eyebrows
8) skin tone moderately tanned

While there are generalisations I think there is also a fair amount of cultural and infancy influence

chris said...

The composite images, on your blog and in the link to Miss Berlin appear airbrushed. Perhaps this is simply a function of the blending, but the skin of the computer generated beauties have no blemishes, perspiration-gloss, or wrinkles.

I moon-light as a wedding photographer. A woman's face sans wrinkles, zits and sweat-sheen has me working overtime in Photoshop.

http://www.flickr.com/photos/cryer/3660549825/in/set-72157620563952296/

Ned Kock said...

Hi Kindke, thanks.

The German site has a section with a list like yours. Check it out; there are some similarities.

Ned Kock said...

Hi Chris.

You are right, and the German researchers acknowledge that as a factor that needs to be controlled for. There is more research on facial attractiveness summarized on their site, and a lot more in the field of evolutionary psychology.

Even when researchers control for blemishes and the like (e.g., by "fixing" the original faces before they show them to raters), there is still a high correlation between the number of original faces used in the averaging and perceptions of beauty.

Ned Kock said...

Btw, those weddings photos are great Chris!

chris said...

Thanks Ned.

Not often we get to discuss aesthetics in the Paleo-shere; though the notion of beauty is ultimately an evolutionary one.

I am new to your blog and have found it to be highly informative. I appreciate your unique perspectives and thorough analysis, as well as your consistently pertinent contributions to others' comments sections.

Your gentle, non-dogmatic tone is a refreshing contrast to the gratuitously high T of many health & fitness bloggers and their readers.

Keep on truckin'

Anna said...

This is why I chose Dr. William Hang's Face Focused approach for my son's orthodontic treatment. Dr. Hang uses orthotropic appliances to guide lower facial growth in young patients for a more pleasing facial appearance and improved airway space/correct oral posture, not just straight teeth. It isn't just about creating attractive faces, though. The goal is improved breathing and oral function for health and athletic performance. More attractive results are just a side benefit of guiding growth the way it should have occurred. He also teaches orthodontists how to use the same methods in the mini-residencies he conducts at his practice.

www.facefocused.com

Dr. Hang is hosting is hosting the 13th International Association for Facial Growth Guidance Symposium in October 2010 in Westlake Village, CA (near Los Angeles). Anyone with an interest in learning more about this subject, but particularly those in the dental and orthodontic professions, is welcome to register. www.iafggsymposium.com for more information.

I have no affiliation with Dr. Hang other than as a satisfied parent of a current patient (and I drive 300 miles round trip for my son's office visits, so you better believe I did my homework on this issue).

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