Archive for the ‘Sociobiology’ Category

What makes some people so much more alluring than others? It appears that good looks and sexiness are determined before we’re even born.

A multitude of studies say that attractive people have it all. As babies they get less chastisement, more cuddles, and better presents. At school they are more popular, have more friends and are less likely to be bullied. And as adults, they have more sexual partners, and are more likely to be married, have a good job, and earn a higher salary. They are also perceived to be healthier, smarter, and more trustworthy, and if they go into politics they are more likely to be elected. But why are some people seen as attractive and others not? And why have we evolved to find some features attractive and others not?

According to new research, it may all be down to oxidative stress and antioxidants. New research has revealed that men who were rated as the most physically attractive by women have the lowest levels of markers of oxidative stress.  (1)

“These findings have several important implications,” says Steven Gangestad who led the study. “They fit in with the idea that women evolved to find particular features attractive because those features are related to low levels of oxidative stress.”

Attractiveness has long been a source of fascination for psychologists, anthropologists, behavioral scientists – and singletons. Some have investigated the many life advantages that come with attractiveness, while others have looked at whether or not it is a learned criterion. The evidence seems clear that attraction to specific features is not learned, but has evolved over time as a way of distinguishing the virile from the weak. This evolutionary perspective is backed up by much a mountain of research, including studies showing that newborn babies have a preference for attractive faces. It’s suggested that physical attractiveness may serve as a biological signal of good health. In ancestral time, being able to spot an attractive, and therefore fit, partner would have carried a huge survival advantage.

Many studies have looked at individual features of attractiveness, from blonde hair and long legs to height, weight, waists and shoulders, but underlying much of the work is what is known as fluctuating asymmetry. Studies have shown that people who have bilateral symmetry, where features on both sides of the body are the same, are judged to be more attractive.

In people with fluctuating asymmetry some body parts are not symmetrical, and one theory is that this imbalance results from something going wrong at key developmental stages. Fluctuating asymmetry is thought to be visible evidence that the person was exposed to some kind of stressor during early development which he or she was not robust enough to withstand. In evolutionary and survival terms, such a man or woman would be less robust and less attractive as a potential partner.

A possible cause of that fluctuating asymmetry is exposure to oxidative stress in the womb which interferes with proper development. The embryo requires energy to develop properly. As cells use oxygen to make energy, they can create free radicals. These are unstable molecules that can have chemical reactions with other molecules, causing the cell damage known as oxidative stress. Free radicals can be kept in check by antioxidants, but if there is an overabundance of radicals, the resulting oxidative stress can damage DNA and tissue. Oxidative stress is thought to be a major cause of mutations and to play a part in ageing and a host of diseases, including cancer.

Overproduction of free radicals, and the resulting oxidative stress, can be triggered by a number of factors. Maternal smoking has been linked to higher levels, as have infections and other factors during pregnancy, including maternal diabetes and obesity.

In the new research reported in the journal Animal Behavior, psychologists at the University of New Mexico looked for signs of oxidative stress in men aged 18 to 38.

Ten bilateral features of the men – ear width, ear height, wrist width, elbow width, lengths of four fingers, ankle breadth and foot breadth – were measured and compared. The men’s urine was measured for markers of oxidative stress and for hormones, and they were quizzed about any birth complications, such as late or premature birth, which can increase levels of oxidative stress. Finally, a group of women were asked to rate images of the men’s bodies and faces for physical attractiveness.

Results show that men who were rated as attractive by the women had significantly lower levels of oxidative stress. And men with more symmetrical bodies had lower levels and were rated as more attractive. Men who had experienced birth problems had higher levels of oxidative-stress markers.

Several researchers have also been looking at specific body shapes and dimensions as markers of desirable qualities in a mate. Various body ratios, especially that of the waist-to-hip size, have also been examined. Some studies have shown that men are especially attracted to women with a low hip ratio – small waists and large hips–just why remains elusive, although suggestions have included better child-bearing abilities, improved health, and greater survival.

Body mass index, a measure of both height and weight, is another dimension that has attracted the attention of researchers. A ratio of 20.85 has been found to be most attractive in women, because, say researchers, it is seen by men as sign of good health and good reproductive potential.

Legs have not escaped the gaze of researchers either. Studies have shown that long legs are preferred in women, while men with legs the same length as the torso are preferred by women. One theory is that long legs are a sign of fitness, with some research suggesting that tall women have wider pelvises than shorter women, allowing easier births and higher birth-weight babies. Longer relative leg length is also associated with reduced risks of heart disease, cancer and diabetes, and lower blood pressure.

It has been argued that women are attracted to men with relatively shorter legs because it makes them look more muscular, and, in evolutionary terms, more useful as a mate.

This ancestral attraction to action men may also be why facial scars in men are seen as attractive, as long as they are the right kind of scar. A facial scar, preferably one that looks like it was inflicted in anger, increases the attractiveness of a man for a short-term relationship, according to a Liverpool University study. (2)

“Women may have rated scarring as an attractive quality for short-term relationships because they found it be a symbol of masculinity, a feature that is linked to high testosterone levels an indicator of good genetic qualities that can be passed on to offspring,” says Rob Burriss, one of the authors of the study. “Men without scars, however, could be seen as more caring and therefore more suitable for long-term relationships.”

Dr. Burriss runs an interesting interactive web site where you can actually participate in one of his facial preference experiments.  See it at

  1. Gangestad, Steve, et al. (2010). Men’s Oxidative Stress, fluctuating asymmetry and physical attractiveness, Animal Behaviour, 10 (10), 1016-1032.
  2. Burriss, R. P., Rowland, H. M., & Little, A. C. (2009). Facial scarring enhances men’s attractiveness for short-term relationships. Personality and Individual Differences, 46, 213-217.

Jim Hatem


Scientists in Australia and Hong Kong have conducted a comprehensive study to discover how different body measurements correspond with ratings of female attractiveness. The study, published in the Journal of Evolutionary Biology, found that across cultural divides young, tall and long armed women were considered the most attractive. (1)

“Physical attractiveness is an important determining factor for evolutionary, social and economic success,” said lead author Robert Brooks from the University of New South Wales. “The dimensions of someone’s body can tell observers if that person is suitable as a potential mate, a long term partner or perhaps the threat they pose as a sexual competitor.”

Traditional studies of attractiveness have been bound to the Darwinian idea of natural selection, which argues that an individual will always choose the best possible mate that circumstances will allow. Such studies have focused on torso, waist, bust and hip measurements. In this study the team measured the attractiveness of scans of 96 bodies of Chinese women who were either students or volunteers, aged between 20-49 years of age.

Videos of the models were shown to a sample of 92 Australian adults, 40 men and 52 women, aged between 18 to 58 years of age, and mostly of European descent. They then compared the attractiveness ratings given by the Australian group to the ratings from a group in Hong Kong to avoid cultural bias.

Both sample groups were asked to rate the models’ attractiveness on a 7 point scale; on average the raters took just 5.35 seconds to rate each model.  The team then explored the statistical results, focusing on age, body weight and a range of length and girth measurements.

The results showed that there was a strong level of agreement between the 4 groups of Australian men and women, and Hong Kong men and women, with scans of younger, taller and lighter women being rated as more attractive.  Women with narrow waists, especially relative to their height, were also considered much more attractive.

The study also revealed that BMI (Body mass index) and HWR (Hip to waist ratio) were both strong predictors of attractiveness.  Scans of taller women who had longer arms were also rated highly, however leg size did not contribute significantly to the ratings.

“Our results showed consistent attractiveness ratings by men and women and by Hong Kong Chinese and Australian raters, suggesting considerable cross cultural consistency,” concluded Brooks.  “In part this may be due to shared media experiences.  Nonetheless when models are stripped of their most obvious racial and cultural features, the features that make bodies attractive tend to be shared by men and women across cultural divides.”

  1. Brooks, R. , et al., 2010.  Multivariate selection on female bodies.  Journal of Evolutionary Biology, 23 (10): 2238-2248.

For years a debate has been going on about the cause of attention deficit hyperactivity disorder (ADHD).  The social scientists have been arguing that it was all about nurture while the real scientists, noting the tendency for the disorder to run in families argued for a genetic cause.  An important new study comes down heavily on the side of biology. (1)

One in 50 children are affected by the disorder, which attracts disapproving looks and frequent scolding from people convinced that the bad behavior is due to poor parenting, too much sugar or too many additives in the child’s diet.

Children with ADHD are impulsive and have an inability to focus, which causes difficulties at home and school, placing immense strain on their families. The burden has been aggravated by the stigma attached to the disorder which attributes responsibility to the parents.

Now scientists from Cardiff University in the UK, say the origin of the behavior is in the genes. They compared the DNA of two groups of children with and without ADHD and have discovered differences between them which provide the first direct evidence of a genetic cause.

In an interview with the BBC, Anita Thapar, professor of child and adolescent psychiatry at Cardiff University, said: “We are really excited by these findings. We have known ADHD runs in families but this is the first evidence of a direct genetic link. We hope these findings will help overcome the stigma associated with ADHD.

“Too often people dismiss it as being down to bad parenting or poor diet. As a clinician it was clear to me this was unlikely to be the case. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to the brains of other children.”

ADHD is known to run in families – identical twins have a three-in-four chance of having the condition if their twin also has it. But, until now, debate has raged over whether the “heritability” of the condition was the result of a shared environment or shared genes.

The researchers analyzed the genomes of 366 children who had been diagnosed by doctors with ADHD and compared them with the genomes of 1,000 controls. They found that chunks of DNA which were either missing or duplicated were twice as common in the children with ADHD. The findings are published in The Lancet.

Professor Thapar said the parts of the genome affected were the same as those involved in autism and schizophrenia, suggesting a potential overlap between the conditions.

“It gives us a window into the biology of the brain. The findings will help unravel the biological basis of the condition and could help develop treatments.”

Treatment for ADHD is limited to alleviating the symptoms with drugs, behavioral management and school support. “It is palliative. It doesn’t cure but it takes the edge off the symptoms. The hope is that by better understanding the biology we can have more specific types of medication,” Professor Thapar said.

She added that there was no evidence that bad parenting or poor diet caused ADHD, although it could affect behavior in other children. “We have looked – but we have found none. To manage children with ADHD you need to be a super-parent to handle the difficulties. But that doesn’t mean the parenting caused the difficulties,” she said.

  1. Rare chromosomal deletions and duplications in attention-deficit hyperactivity disorder: a genome-wide analysis
    Dr Nigel M Williams PhD,Irina Zaharieva BSc,Andrew Martin BSc,Kate Langley PhD,Kiran Mantripragada PhD,Ragnheidur Fossdal PhD,Hreinn Stefansson PhD,Kari Stefansson MD,Pall Magnusson MD,Olafur O Gudmundsson MD,Omar Gustafsson PhD,Prof Peter Holmans PhD,Prof Michael J Owen MD,Prof Michael O’Donovan MD,Prof Anita Thapar MD
    The Lancet – 30 September 2010
    DOI: 10.1016/S0140-6736(10)61109-9

From feckless fathers and teenage mothers to so-called feral kids, the media seems to take a voyeuristic pleasure in documenting the lives of the “underclass”. Whether they are inclined to condemn or sympathize, commentators regularly ask how society got to be this way. There is seldom agreement, but one explanation you are unlikely to hear is that this kind of “delinquent” behavior is a sensible response to the circumstances of a life constrained by poverty. Yet that is exactly what evolutionary biologists are now proposing.

There is no reason to view the poor as stupid or in any way different from anyone else.  All of us are simply organisms genetically programmed to make the best of the hand that life has dealt us.  Of course, that means, programmed to use the best strategy for leaving copies of our genes behind.

Evolutionary theory predicts that if you are a mammal growing up in a harsh, unpredictable environment where you are susceptible to disease and might die young, then you should follow a “fast” reproductive strategy – grow up quickly, and have offspring early and close together so you can ensure leaving some viable progeny before you become ill or die. For a range of animal species there is evidence that this does happen. Now research suggests that humans are no exception.  And why should it, anyway?

Certainly the theory holds up in comparisons between people in rich and poor countries. Bobbi Low and her colleagues at the University of Michigan at Ann Arbor compared information from nations across the world to see if the age at which women have children changes according to their life expectancy (1). “We found that the human data fit the general mammalian pattern,” says Low. “The shorter life expectancy was, the earlier women had their first child.”

But can the same biological principles explain the difference in behavior between rich and poor within a developed, post-industrialized country? Danielle Nettle of the University of Newcastle in the UK, believes it can. In a study of over 8000 families, Nettle found that in the most deprived parts of England people can barely expect 50 years of healthy life, nearly two decades less than in affluent areas. And sure enough, women from poor neighborhoods are likely to have their babies at an early age and in quick succession. They have smaller babies and they breastfeed less, both of which make it easier to get pregnant again sooner (2).

“If you’ve only got two-thirds as much time in your life as someone in a different neighborhood, then all of your decisions about when to start having babies, when to become a grandparent and so on have to be foreshortened by a third,” says Nettle. “So it shouldn’t really surprise us that women in the poorest areas are having their babies at around 20 compared to 30 in the richest ones. That’s exactly what you would expect.”

Consciously or subconsciously, women do seem to take their future prospects into account when deciding when to start having children. At a meeting last year, Sarah Johns at the University of Kent in Canterbury, UK, reported that in her study of young women from a range of socioeconomic backgrounds in Gloucestershire, UK, those who perceived their environment as risky or dangerous, and those that thought they might die at a relatively young age, were more likely to become mothers while they were in their teens. “If your dad died of a heart attack at 45, your 40-year-old mum has got chronic diabetes and you’ve had one boyfriend who has been stabbed, you know you’ve got to get on with it,” she says.

It’s the same story in the US. The latest figures, from 2005, reveal that teenage motherhood accounts for 34 per cent of first births among the poor. Arline Geronimus of the University of Michigan at Ann Arbor, who has studied health inequalities and reproductive patterns, points out that healthy life expectancy is short for poorer Americans and women depend on extended family networks for support. This means it is in their interests to have children while they still have relatives in good physical shape to help out.

The shockingly rapid deterioration in health experienced by women in poor neighborhoods also directly affects mothers. Even women in their 20s have an increased risk of conditions such as hypertension that would reduce the chance of a healthy pregnancy and birth. In research carried out in the late 1990s, Geronimus and her colleagues found that in Harlem, a poor neighborhood in New York City, the infant mortality rate for babies born to mothers in their 20s was twice that of the babies of teenage mothers (3).

It is not simply a case of teenage girls from deprived backgrounds accidentally becoming pregnant. Evidence from many sources suggests that teen pregnancy rates are similar in poor and affluent communities. However, motherhood is a choice, as both Geronimus and Johns are keen to point out. Teenage girls from affluent backgrounds are more likely to have abortions than their less-privileged peers. In terms of reproduction, the more affluent girls are best off concentrating on their own career and development so that they can invest more in the children they have at a later stage. “It seems that girls are assessing their life chances on a number of fronts and making conscious decisions about reproduction,” says Johns.  I would argue that these decisions only seem to be conscious.  The conscious behavior is a reproductively wise choice and genes hell-bent on leaving copies of themselves behind are working behind the scenes.

Another important issue is whether or not a girl’s father is around when she is growing up. Developmental psychologist Bruce Ellis, of the University of Arizona in Tucson, has studied extensively the effects of girls’ relationships with their fathers. His research shows that the less involved a father is with his daughter from an early age, and the less warm the relationship, the earlier she starts having sex and, potentially, babies (4).

Fathers in deprived neighborhoods are more likely to be absent, which very likely is because they are following “fast” strategies of their own. They are doing what they are biologically inclined to do in such an environment.  These include risky activities designed to increase their wealth, prestige and dominance, allowing them to compete more successfully with other men for sexual opportunities. These needn’t necessarily be antisocial, but often they are. “I’m thinking about crime here, I’m thinking about gambling,” says Nettle, and other risky or violent behaviors that we know are typical of men in rough environments. .  I am reminded here of Tony Montoya, as played by Al Pacino, in Scarface: “First you get the money, then you get the power, then you get the women.”  A fast strategy also means a father is less likely to stick with one woman for the long term, reducing his involvement with his children.  That is unfortunate, since a father’s involvement not only delays his daughter’s reproduction but also has a big impact generally on the life chances of his children. In a study of 17,000 people in the UK born in a single week in March 1958, Nettle found that where father involvement was greater, children had significantly higher IQ scores at age 11 and increased upward social mobility through adulthood (5).  Lower investment in children, whether it be through the absence of dad, less breastfeeding from mom, or less parental attention generally because there are more children in the family, comes at a high cost to the children themselves. For one thing, Nettle’s large-scale study of families in England found that babies born in the poorest areas have slower cognitive development, which compromises their education and prospects later in life.

To all this you might ask the question, aren’t poor people bringing their problems on themselves? If only they would wait a while before starting to have babies they might be able to invest more in each one, providing a better diet and healthier lifestyle. It is not so simple. “Children of low income, low education families don’t do well regardless of what their parents’ age is,” says Johns. What’s more, youngsters who delay parenthood may actually be worse off. “In a US study looking at pairs of low-income sisters, the ones that became mothers in their teens quite often did better [in terms of employment and earnings] because they had something to focus their energy into and create a better life for.”

Nettle agrees: “Overwhelmingly the poverty into which a baby is born is going to be a big influence, whatever the age of the mother. It may be that there’s not much pay-off for waiting and doing other, more middle-class behaviors that public health people want to encourage the poor to do.”

People in deprived areas face two kinds of hazard, Nettle says. First, there are constraints on what they are able to do to mitigate their situation. Diet is a prime example: “It’s much more expensive to get 2000 calories a day from fresh fruit and vegetables compared with eating junk food,” Nettle says. Then the environment is often physically more dangerous and unhealthy. “People are doing more dangerous jobs. There is probably more air pollution, more car accidents, a higher crime rate, poorer housing – things you cannot really do much about, which trigger a downward spiral of faster living and less attention to health.”

Once you are in a situation where the expected healthy lifetime is short whatever you do, then there is less incentive to look after yourself. Investing a lot in your health in a bad environment is like spending a fortune on maintaining a car in a place where most cars get stolen anyway, says Nettle. It makes more sense to live in the moment and put your energies into reproduction now.

Evolutionary theory can explain these behavioral responses to poverty, but it doesn’t make them desirable. So what is the answer? What can be done to help people escape from the slippery slope of poor health, poor education and deprivation?  I don’t know but no amount of money poured into sex education and parenting classes will change the situation if young people don’t see a decent future for themselves.  Expensive education schemes and handing out morning after pills are not the answer.  The problem is written in our genetic code and the search for an answer should focus there as well.

1. Cross-Cultural Research, vol 42, p 201

2. Behavioral Ecology, DOI: 10.1093/beheco/arp202

3. Political Science Quarterly, vol 112, p 405

4. New Scientist, 14 February 2007, p 38

5. Evolution and Human Behavior, vol 29, p 416

6. The Journal of the American Medical Association, vol 290, p 2023

Out shopping

Of course, it comes as no surprise to me since I habitually see the world through the lens of evolutionary biology but new research suggests that ovulating women unconsciously buy sexier clothes. The new research comes from the University of Minnesota’s Carlson School of Management. The study found that ovulating women unconsciously dress to impress – doing so not to impress men, but to outdo rival women during the handful of days each month when they are ovulating.

“The desire for women at peak fertility to unconsciously choose products that enhance appearance is driven by a desire to outdo attractive rival women,” says Kristina Durante, a post-doctoral fellow at the Carlson School. “If you look more desirable than your competition, you are more likely to stand out.”

This research, forthcoming in the Journal of Consumer Research, provides some of the first evidence of how, why, and when consumer behavior is influenced by hormonal factors. Durante and co-authors focused their predictions on the fact that competition for a suitable partner would be influenced by a woman’s fertility status.

“We found that, when ovulating, women chose sexier fashion products when thinking about other attractive, local but not distant women,” says Durante. “If you are in New York, a woman who lives in LA isn’t going to be seen as competition.”

Although the end result is to attract the best romantic partner available, Durante’s research found that ovulating women’s choice of dress is motivated by the other women in their environment. “In order to entice a desirable mate, a woman needs to assess the attractiveness of other women in her local environment to determine how eye-catching she needs to be to snare a good man,” Durante says.

In the study, researchers had ovulating women view a series of photographs of attractive local women and then asked them to choose clothing and accessory items to purchase. The majority of participants chose sexier products than those who had been shown photographs of unattractive local women or women who lived over 1000 miles away. This change in consumer choice is not a conscious decision and non-ovulating women are not subject to the effect.

The current findings have practical implications for marketers because ovulatory cycle effects may profoundly influence women’s consumer behavior. “For about five to six days every month, normally ovulating women—constituting over a billion consumers—may be especially likely to purchase products and services that enhance physical appearance,” says Durante. Such products include not only clothing, shoes, and fashion accessories, but also cosmetics, health supplements, fitness products, medical procedures, and more.

The paper “Ovulation, Female Competition, and Product Choice: Hormonal Influences on Consumer Behavior,” forthcoming in the Journal Consumer Research, was co-authored by Kristina Durante and Vladas Griskevicius at the Carlson School of Management, Sarah E. Hill (Texas Christian University), Carin Perilloux (University of Texas, Austin) and Norman Li (Singapore Management University).

The Picture Tells the Whole Story

Posted: September 20, 2010 in Sociobiology

A friend sent me this photo.  Apparently it was taken outside an apartment building in Moscow.  Don’t know the details but I think the picture tells the whole story.

I always said that females are attracted to three things in choosing a mate: money, power, and fame.  This, of course, is all heavily documented in sociobiological literature.  However, the absence of these three attributes does not doom a guy to loneliness.  One must not forget the role that physical prowess plays (even though it usually leads to the accumulation of the three attributes I mentioned).  Here is a bit of somewhat amusing evidence.

These Dance Moves Are Irresistible – ScienceNOW.