Progress Daily

As human societies grow richer, people have fewer children. In most species, such an increase in available resources leads in the opposite reproductive direction. What makes the “demographic transition” even more paradoxical is that in less developed times and places, the rich do not have smaller families than the poor.

Most explanations of the demographic transition are social, and none is really satisfactory.

A study by Agnar Helgason, of deCODE Genetics, has recently provided a new explanation: that the mixing-up of people caused by the urbanisation which normally accompanies development is, itself, partly responsible — because it breaks up optimal mating patterns.

Iceland’s records since its founding by a few Vikings are so good that the antecedents of today’s inhabitants (apart from a handful of recent immigrants) are known with precision. Its medical records are also good, and most Icelanders have given genetic samples to deCode.

The study’s principal finding is that the most fecund marriages are between distant cousins. The optimum degree of outbreeding (measured in terms of the number of children and grandchildren produced) lay somewhere between cousins of the third and fourth degrees.

(”Kissing cousins, missing children,” The Economist)

Icelandic women born between 1800 and 1824 who mated with a third cousin had significantly more children and grandchildren (4.0 and 9.2, respectively) than women who hooked up with someone no closer than an eighth cousin (3.3 and 7.3). Those proportions held up among women born more than a century later when couples were, on average, having fewer children.

Despite the general pattern for reproductive success favoring close kinship, couples that were second cousins or more closely related did not have as many children.

With close inbreeding — between first cousins — there is a significant increase in the probability that both partners will share one or more detrimental recessive genes, leading to a 25 percent chance that these genes will be expressed in each pregnancy.

Mating with a relative might reduce a woman’s chance of having a miscarriage caused by immunological incompatibility between a mother and her child. Some individuals have an antigen (a protein that can launch an immune response) on the surface of their red blood cells called a rhesus factor. In some cases — typically during a second pregnancy — when a woman gets pregnant, she and her fetus may have incompatible blood cells, which could trigger the mother’s immune system to treat the fetus as a foreign intruder, causing a miscarriage. This occurrence is less probable if the parents are closely related, because their blood makeup is more likely to match.

It may be that the enhanced reproductive success at the level of third and fourth cousins (who on average would be expected to have inherited 0.8 percent to 0.2 percent of their genes from a common ancestor) represents a point of balance between the competing advantages and disadvantages of inbreeding and outbreeding.

(”When Incest Is Best,” by Nikhil Swaminathan)

Dr Randy Thornhill manipulated pictures to make people’s faces appear more and less symmetrical, then asked volunteers of the opposite sex rank them for attractiveness. Symetery and attractiveness correlated. His later experiments have shown that all aspects of bodily symmetry contribute, down to the lengths of corresponding fingers, and that the assessment also applies to those of the same sex.

Perfect symmetry is hard for a developing embryo to maintain, so one that can maintain it must have good genes (and luck).

Other aspects of beauty, too, are indicators of health. Skin and hair condition are sensitive to illness and malnutrition.

Leslie Zebrowitz and Gillian Rhodes found 9 past studies on attractiveness and IQ, and subjected them to a “meta-analysis.”

The studies’ researchers had photographed people and asked them to do IQ tests, then showed the photographs to other people and asked them to rank the intelligence of the first lot. The results suggested that people get such judgments right often enough to be significant.

Dr Daniel Hamermesh presided over a series of surveys in the USA and Canada that showed that when all other things are taken into account, ugly people earn less than average incomes, while beautiful people earn more than the average. The ugliness “penalty” for men was -9% while the beauty premium was +5%. For women, the ugliness penalty was -6% while the beauty premium was +4%.

He found the figures for men in Shanghai are –25% and +3%; for women they are –31% and +10%. In Britain, ugly men do worse than ugly women (-18% as against -11%) but the beauty premium is the same for both (+1%).

Dr Hamermesh found that those members of a particular (anonymous) US law school rated attractive on the basis of their graduation photographs went on to earn higher salaries. Moreover, lawyers in private practice tended to be better looking than those working in government departments.

Hamermesh’s study of Dutch advertising firms showed that those with the most beautiful executives had the largest size-adjusted revenues — a difference that exceeded the salary differentials of the firms in question. Finally, he found that attractive candidates were more successful in elections for office in the American Economic Association.

Working in Shanghai, where his research indicated the difference between the ugliness penalty and the beauty bonus was greatest, Dr Hamermesh looked at how women’s spending on their cosmetics and clothes affected their income.

The beauty premium generated by such primping was worth only about 15% of the money expended.

Niclas Berggren’s research team looked at almost 2,000 candidates in Finnish elections. They asked foreigners (mainly Americans and Swedes) to examine the candidates’ campaign photographs and rank them for beauty. The more beautiful candidates, as ranked by people who knew nothing of Finland’s internal politics, tended to have been the more successful — the effect was larger for women than for men.

“To those that have, shall be given,” The Economist

For a couple of years, researchers (Ray Fisman, Sheena Iyengar, Itamar Simonson, and Emir Kamenica) ran a speed-dating experiment at a local bar just off the Columbia campus.

Subjects were asked to rate their partners’ intelligence, looks, and ambition after each meeting. Each event had between 10 and 20 daters of each gender, and in the course of the evening, every man met every woman and vice versa.

The researchers collected data on thousands of decisions made by more than 400 daters from Columbia University’s graduate and professional schools.

They found that men put significantly more weight on their assessment of a partner’s beauty, when choosing, than women did.

Intelligence ratings were more than twice as important in predicting women’s choices as men’s. Men tended to prefer women whom they rated as relatively smart and ambitious but they avoided women whom they perceived to be smarter and more ambitious than themselves.

When women were the ones choosing, the more intelligence and ambition the men had, the better.

Women of all races (white, black, East Asian, and Hispanic) revealed a strong preference for men of their own race. But a woman’s race had little effect on the men’s choices.

The researchers found no evidence of a white male preference for East Asian women. But did find that East Asian women did not discriminate against white men (only against black and Hispanic men). So the white man-Asian woman pairing was the most common form of interracial dating. Daters of both sexes from south of the Mason-Dixon Line revealed much stronger same-race preferences than Northern daters.

“An Economist Goes to a Bar,” by Ray Fisman

Women — especially in the developed world — are getting married and having kids later than ever before. According to the UN’s World Fertility Report, the worldwide median age of marriage for women is up two years, from 21 in the 1970s to 23 today. In the developed countries, the rise has been from 22 to 26.

In 1960, 70% of American 25-year-old women were married with children. In 2000, only 25% were. In 1970, just 7% of all American 30- to 34-year-olds were unmarried. Today, the number is 22%. In today’s Hungary, 30% of women in their early thirties are single, compared with 6% of their mothers’ generation at the same age. In South Korea, 40% of 30-year-olds are single, compared with 14% only 20 years ago.

Between 1960 and 2000, the percentages of 20-, 25-, and 30-year-olds enrolled in school more than doubled in the US, and enrollment in higher education doubled throughout Europe. The majority of college students are female in the US, UK, France, Germany, Norway, and Australia, and the gender gap is quickly narrowing in more traditional countries like China, Japan, and South Korea. In Denmark, Finland, and France, over 1/2 of all women between 20 and 24 are in school.

In the UK, close to 1/3 of 30-year-old college-educated women are unmarried. In Spain, women now constitute 54% of college students, up from 26% in 1970, and the average age of first birth has risen to nearly 30, which may be a world record.

In the US, the proportion of unmarried 20-somethings living with their parents has declined steadily over the last 100 years, despite rising rents and real estate prices.

A 2005 report from MasterCard finds that women take 4 out of every 10 trips in the Asia-Pacific region — up from 1 in 10 back in the mid-’70s.

Canadian single women are buying homes at twice the rate of single men. The National Association of Realtors reports that in the US last year, single women made up 22% of the real-estate market, compared with only 9% for single men. The median age for first-time female buyers: 32.

Between 1994 and 2004, the number of Japanese women between 25 and 29 who were unmarried soared from 40% to 54%. The number of 30- to 34-year-old females who were unmarried rose from 14% to 27%.

A majority of Japanese single women between 25 and 54 say that they’d be just as happy never to marry.

Under European Communist rule, women tended to marry and have kids early. In the late ’80s, the mean age of first birth in East Germany, for instance, was 25, while the West German average was 28. Tying the knot was the only way to gain independence from parents, since married couples could get an apartment, while singles could not. Furthermore, access to modern contraception, which the state proved either unable or unwilling to produce at affordable prices, was limited. Marriages frequently began as the result of unplanned pregnancies.

Many towns in what used to be East Germany now face a lack of women, as women who excelled in school have moved west for jobs. In some towns, the ratio is just 40 women to 100 men. Women constitute the majority of both high school and college graduates in Poland.

Save Albania, no European country stood at or above replacement levels (2.1 children) in 2000. Three-quarters of Europeans now live in countries with fertility rates below 1.5, and even that number is inflated by a disproportionately high fertility rate among Muslim immigrants. Oddly, the most Catholic European countries — Italy, Spain, and Poland — have the lowest fertility rates, under 1.3. In Japan, fertility rates are about 1.3. Hong Kong, at 0.98 has broken the barrier of one child per woman.

With fewer children, the labor force shrinks, and so do tax receipts. Europe today has 35 pensioners for every 100 workers. By 2050, those 100 may be responsible for 75 pensioners.

By large margins, surveys suggest, US women want to marry and have kids. US fertility rates are lower than replacement level among college-educated women, but are still higher than those of most rich countries (including Sweden and France).

Young women in Vietnam have begun putting off marriage and fertility rates have fallen from 3.8 children in 1998 to 2.1 in 2006.

Fertility rates have dropped below replacement level in several of India’s major cities.

“The New Girl Order,” by Kay S. Hymowitz

The largest-ever global study of abortion (”Abortion: Worldwide Levels and Trends“) has found that restricting abortions has little effect on the number of pregnancies terminated. Rather, it drives women to seek illegal, often unsafe backstreet abortions leading to an estimated 67,000 deaths a year. A further 5m women require hospital treatment as a result of botched procedures.

In Africa and Asia, where abortion is generally either illegal or restricted, the abortion rate in 2003 was 29 per 1,000 women aged 15-44. This is almost identical to the rate in Europe — 28 — where legal abortions are widely available. Latin America, which has some of the world’s most restrictive abortion laws, is the region with the highest abortion rate (31), while western Europe, which has some of the most liberal laws, has the lowest (12).

A woman’s likelihood of having an abortion is similar whether she lives in a rich country (26 per 1,000) or a poor or middle-income one (29).

The same point can be made by looking at those countries which have changed their laws. Between 1995 and 2005, 17 nations liberalised abortion legislation, while three tightened restrictions. The number of induced abortions nevertheless declined from nearly 46m in 1995 to 42m in 2003, resulting in a fall in the worldwide abortion rate from 35 to 29. The most dramatic drop — from 90 to 44 — was in former communist Eastern Europe, where abortion is generally legal, safe and cheap. This coincided with a big increase in contraceptive use.

According to a report published this month by Population Action International women in poor countries are 250 times more likely to die in pregnancy or childbirth than women in rich ones.

A woman in Africa has a one in 16 chance of dying in pregnancy or childbirth, compared with one in 3,800 for a woman in the rich world.

“Safe, legal and falling,” The Economist

From the Stone Age to 1800, there was no gain in average living conditions. Now incomes rise steadily.

The average Briton in 1788 ate only as many calories a day as hunter-gatherers (2,300). And the British diet was more monotonous. Life expectancy was only slightly above that of hunter-gatherers (38 years). Height is a good guide to nutrition and health: men in England averaged 5ft 6in, the same as males in the Stone Age. Men then worked 60 hours a week. Compared to hunter-gatherers’ 35 hours.

Englishmen who were economically successful, from the Middle Ages to 1800, left 4 or 5 surviving children at their deaths. In contrast, landless labourers left fewer than 2 children.

Preindustrial England was thus a world of constant downward mobility. Given the static nature of the preindustrial economy, the superabundant children of the rich had to, on average, move down the social hierarchy to find work. Attributes that ensured later economic dynamism – hard work, ingenuity, innovativeness, education – were thus spread throughout the population.

From 1200 to 1800 interest rates fell, murder rates declined, work hours increased, the taste for violence declined, and numeracy and literacy spread to even the lower reaches of society.

In both preindustrial Japan and China the rich had more children than the poor, but in a more modest way. The samurai in Japan in the Tokugawa era (1603-1868), for example, produced on average little more than one son per father.

In modern affluent societies, the higher income a person has, on average, the less leisure he has. The source of our compulsion to work may lie in our ancestors’ passage through a preindustrial world that rewarded a compulsion to work and accumulate with reproductive success.

“England’s success may be in our genes,” Gregory Clark

The average IQs of adult men and women are about the same. But there are more men at the top levels of ability. And more males with very low IQs. The pattern with mental retardation is the same: as you go from mild to medium to extreme, the preponderance of males gets bigger.

The male distribution of height is also flatter, with more very tall and very short men.

Research by Jacquelynne Eccles has repeatedly concluded that the shortage of females in math and science reflects motivation more than ability.

Average gender differences in abilities tend to be extremely small. But there are significant differences in motivation. For example, Roy Baumeister’s survey of published research found that almost every measure and every study has shown higher sex drive in men.

And according to another study, over 80% of the people who work 50-hour weeks are men.

According to recent research using DNA analysis, today’s human population is descended from approximately twice as many women as men. Throughout the entire history of the human race, approximately 80% of women but only 40% of men reproduced.

Since women’s odds of reproducing have been good, the optimal strategy has been to minimize risks.

But most men who ever lived did not have descendants who are alive today.

Also, while few women have had more than a dozen children, some men have had hundreds.

If a group loses 1/2 its men, the next generation can still be full-sized. But if it loses 1/2 its women, the size of the next generation will be severely curtailed. Hence most cultures keep their women out of harm’s way while using men for risky jobs.

The US Department of Labor statistics report that 93% of the people killed on the job are men. Of the first 3,000 Americans killed in Iraq, 2,938 were men, 62 were women.

“Is There Anything Good About Men?,” by Roy F. Baumeister

Steve Cole and John Cacioppo, used a “gene chip” to look at the DNA of isolated people and found that people who described themselves as chronically lonely have distinct patterns of genetic activity, almost all of it involving the immune system.

The study does not show which came first — the loneliness or the physical traits.

Many studies of large populations have shown that people who describe themselves as lonely or as having little social support are more likely to die prematurely and to have infections, high blood pressure, insomnia and cancer.

When the researchers studied and compared all 22,000 human genes, 209 stood out in the loneliest people.

Many of the these genes seemed to be involved in the basic immune response to tissue damage and others were involved in the production of antibodies (the tag the body uses to mark microbes or damaged cells for removal), suggesting that the loneliest people had unhealthy levels of chronic inflammation, which has been associated with heart and artery disease, arthritis, Alzheimer’s, etc.

“Sick? Lonely? Genes tell the tale,” Reuters

Norbert Schwarz, et al., calculates “gross national happiness” by using the day reconstruction method in which people are asked to recollect memories of the previous working day by writing a short diary.

They are told to think of their day as a series of episodes in a film and are asked a series of questions about how they felt during each event or activity.

They then give a mark on their enjoyment of each episode on a scale of one to 6. The totals are divided by the number of hours taken by each activity to produce a simple score for the day.

The researchers assessed how 909 US working women felt during 28 types of activity and found that sex, relaxing with friends and having lunch with colleagues brought the most enjoyment. This was followed by watching television alone, shopping with a spouse and cooking on their own.

Commuting, housework and too much contact with their boss rated as the least pleasant activities.

Taking care of children was also among the less enjoyable activities.

Norbert Schwarz: “When we sample all the times that parents spend with their children, the picture is less positive than parents expect. Saying that you generally don’t enjoy spending time with your kids is terrible but admitting that they were a pain last night is quite acceptable.”

Women who slept poorly, on average, enjoyed their day as little as a typical person enjoys commuting. Those who usually slept well enjoyed their day as much as most people enjoy watching television. Tight work deadlines were also a powerful factor in upsetting women’s daily moods.

General life circumstances — such as wealth, job security, or whether someone is single or married — had a relatively small impact on happiness.

As long as the women were not battling poverty, income did not have an influence.

“[C]ommuting is a very negative experience that takes up considerable time every day. Income, however, has relatively little influence on daily feelings. You may be better off arranging for more sleep than working for a pay rise.”

People spent the bulk of their waking hours engaged in the activities they enjoyed the least, including work, housework and commuting.

“Happiness is the new economics,” Sarah-Kate Templeton

In every society at all historical times, men’s tendency to commit crimes and other risk-taking behavior rapidly increases in early adolescence, peaks in late adolescence and early adulthood, rapidly decreases throughout the 20s and 30s, and levels off in middle age.

The same age profile characterizes every quantifiable human behavior that is public (i.e., perceived by many potential mates) and costly (i.e., not affordable by all sexual competitors). The relationship between age and productivity among male jazz musicians, male painters, male writers, and male scientists is essentially the same as the age-crime curve. Their productivity quickly peaks in early adulthood, and then equally quickly declines throughout adulthood. The age-genius curve among their female counterparts is much less pronounced; it does not peak or vary as much as a function of age.

Both crime and genius are expressions of young men’s competitive desires, whose ultimate function in the ancestral environment would have been to increase reproductive success.

“Ten Politically Incorrect Truths About Human Nature,” by Alan S. Miller Ph.D., Satoshi Kanazawa Ph.D.