Professor Petrie theorised that since genetic mutations can occur anywhere in the genome, some will affect the 'DNA repair kit' possessed by all cells. As a result, some individuals have less efficient repair kits, resulting in greater variation in their DNA as damage does unrepaired.
Although unrepaired DNA is generally harmful - causing tissue to degenerate or develop cancers - it is useful in some parts of the genome, such as those parts resposible for disease defence where variation can help in the resistance to disease. It has long been known that greater variation of DNA in the disease defending regions makes it more likely that an individual can resist attacks by bacteria and viruses.
Larger, older swordtail females prefer asymmetrical males. Morris wondered if this might have to do with how the males had grown. So she and her team tested fish. They fed some males high-quality food and others low-quality food. Certain males grew faster on high-quality food.
And those fast-growing males ended up with uneven bars on their sides. Asymmetry may show that a male has put his energy into rapid growth, Morris says. For example, a fish living near lots of predators would be more likely to survive if it grew faster. It would also be better off if it could grow even when food is scarce. So females that live in one of these types of environments should prefer asymmetrical males, Morris explains.
Those males would carry the best genes for their environment, and would later pass them on to their young. Research on birds also shows that female birds prefer good-looking guys. For example, among satin bowerbirds, females prefer males whose feathers reflect more ultraviolet UV light. Researchers at Auburn University in Alabama caught male bowerbirds and took blood samples. Males with blood parasites had feathers reflecting less UV light than healthy males. They were using that information to find healthy males to father their young.
Adeline Loyau is a behavioral ecologist who has seen similar things in peacocks. These are the vivid circles at the ends of their tail feathers. She knew peahens prefer males with more eyespots. They also prefer males that show off their tails more.
Her work has now shown that healthier peacocks have more eyespots in their tails. These birds also splay their flashy tails more frequently to the females. Loyau then gave some males an injection that made their immune systems leap into action. It was as if they were sick. These peacocks displayed their tails less than the healthy guys did. But that was only true if they had fewer eyespots. Females are better off avoiding sick mates, she explains.
A female bird, she adds, also looks for good genes in the guy who will father her young. For example, it may help us find healthy mates. Langlois and her team in Texas studied this question using a technique called EEG. EEGs measure electrical activity in the brain using a net of small electrodes placed on the outside of the head. The scientists recruited college students for their brain study.
Each student looked at a series of faces while wearing the electrode net. Human faces fell into one of three groups: highly attractive, unattractive or digitally morphed images that combined many features into an average face. Some chimpanzee faces were put in the mix too. The EEG recorded brain activity as each student viewed the pictures. The researchers then searched the EEGs for patterns of electrical activity. Those patterns offered signs of what the brain was doing. That makes sense, the researchers now say, because people are more familiar with human faces.
The team also found that brains processed very attractive faces faster than unattractive ones. And they processed average faces even faster. Subjects also rated the averaged faces as most attractive.
In sum, looks may go far more than skin deep after all. They also can affect how people interact. Scientists discovered long ago that people show favor to those with a pretty face.
Attractive people are more likely to get jobs. They make more money than their less attractive coworkers. Together, these phenomena should cause faces in a group to appear more like the group average than when presented alone, and that group average should tend to be more attractive than the individual faces, on average. Notably, though, the effect did not depend on the number of faces in the group. Any size group should do. Good only if it's serendipitous of course, and not because you're consciously cultivating a friend group that mitigates your physical insecurities.
Nervous laughter. The nice part of the idea is that it might give us another excuse to socialize and travel in numbers. For almost all people, relationships are integral to health, and time spent socializing offline correlates with quality of life. Maybe we actually look more attractive among friends not solely because of complementary bone structures, but because we're happier.
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