Third cousin couples have the most children and grandchildren

Blogging on Peer-Reviewed ResearchMarriage between closely related cousins is a heavy taboo in many cultures and its critics often cite the higher risk of genetic diseases associated with inbreeding. That risk is certainly apparent for very close relatives, but a new study from Iceland shows that very distant relatives don’t have it easy either. In the long run, they have just as few children and grandchildren as closely related ones.

Shuffling the genetic deck

Indian marriageSex chromosomes aside, every person has two copies of each gene, one inherited from their father and one by their mother. Not every gene will be in correct working order, but there’s a good chance that a faulty copy will be offset by a functional one from the other parent.

However, if two parents are closely related, there’s a higher-than-average chance that they will already share some of the same genes and a similarly increased chance that their child will receive two defective copies. That can be very bad news indeed and in cases where important genes are affected, the results can include miscarriage, birth defects or early death.

Sex, then, is a shuffling of their genetic deck and theoretically the more closely related the partners are, the greater the chance that their child will be dealt a dud hand. And yet, some studies have found that some closely related couples actually do better than distant relatives in terms of the number of children they manage to raise. This trend is certainly unexpected and the big question is whether it is the result of biology or money.

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Predicting ethnic violence – why good neighbours need good fences

Everybody, apparently, needs good neighbours, but in many parts of the world, your neighbours can be your worst enemy. In the past century, more than 100 million people have lost their lives to violent conflicts. Most of these were fought between groups of people living physically side by side, but separated by culture or ethnicity.

Good fences make good neighboursNow, May Lim and colleagues from the New England Complex Systems Institute have developed a mathematical model that can predict where such conflicts by looking at how different groups are spread out in a given area.

According to their research, violence is most likely to erupt in areas with poorly-defined boundaries between large and culturally different groups. Their model predicted areas of ethnic violence in both India and Yugoslavia with uncanny accuracy, and Lim hopes that it will help policymakers to look at the problem of violent conflicts with a scientific eye.

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Five-month-old babies prefer their own languages and shun foreign accents

Discriminating against people who do not speak your language is a big problem. A new study suggests that the preferences that lead to these problems are hard-wired at a very young age. Even five-month-old infants, who can’t speak themselves, have preferences for native speakers and native accents.

The human talent for language is one of our crowning evolutionary achievements, allowing us to easily and accurately communicate with our fellows. But as the Biblical story of the Tower of Babel relates, linguistic differences can serve to drive us apart and act as massive barriers between different social groups.

The Tower of Babel story highlights the conflicts that can arise when people don’t speak the same language.These barriers can give rise to linguistic discrimination, a far more insidious problem that it seems at first. Language-based prejudices have led to horrific acts of human abuse, and even civil wars. Genocide often finds itself paired with linguicide, since a race can be killed off more thoroughly if their language follows them.

Even today, people in a linguistic minority can find themselves denied access to healthcare, or at a disadvantage when looking for jobs. The issue cuts to the heart of several ongoing debates, from the role of second languages in education to whether immigrants must become fluent in the tongue of their host country.

Early preferences

It should therefore be unsurprising to learn that we have strong preferences for our own language and for those who speak it. But Katherine Kinzler and colleagues from Harvard University, have found that we develop these preferences from an incredibly young age, before we can speak ourselves, and well before we can even hope to understand the social issues at stake.

Kinzler tested 24 infants, aged 5 to 6 months, from households that only spoke English, to see if they had any linguistic preferences. Each toddler watched videos of two women, one speaking English and the other, Spanish. The women were all bilinguals and swapped the language they used in different trials to make sure that the babies weren’t showing preferences for physical traits like skin colour.

The babies were then shown the two women side by side, but no longer speaking. They strongly expressed their preference for the English speakers by gazing at their screen for a longer time (measuring gaze time like this is a standard test used by child psychologists).

Once developed in early infancy, these preferences stick around into childhood, and most probably well beyond that. In very similar experiments, Kinzler found that older infants (10 months or so) prefer to accept toys from a woman who spoke their native language.

Even young infants can discriminate between their language and others.The babies, from either Boston or Paris, were shown alternating films of an English or French-speaking woman, who spoke for a while and then silently offered the child a toy. Two real toys then appeared on the table in front of the infant, and they were twice as likely to pick the one in front of the native speaker.

So even though the offering of the toy involved no spoken words, the infants still gravitated towards the woman who had spoken earlier in their familiar tongue.

Different accents

Infants can even pick up on subtle differences in dialect. Even when two speakers are talking in the same language, 5-month old infants will prefer someone who speaks with a native accent to someone who speaks with a foreign twang. Older children (5 years or so) will similarly prefer to befriend another child who speaks with the same accent.

At that age, children will have barely any understanding of the social circumstances that leads to different groups of people speaking the same language in different ways. And it’s unlikely that their parents had much influences, since even the 5-month-old toddlers had these preferences.

These early preferences can act as the foundations for more destructive behaviours and conflicts later on in life. But we must be very careful – an instinctive basis for a behaviour does not in any way justify it.

Instead, by telling us about the basis of linguistic prejudices, these results suggest that we must work even harder to overcome them. If they are hard-wired from an early age, then education from an early age seems like a sensible first step.

Perhaps, exposure to multiple languages early in life can soften these preferences, and it would be fascinating to see if the same results hold for babies from bilingual households.

More on languages, child development, and social conflicts:
Babies can tell apart different languages with visual cues alone
Experience tunes a part of the brain to the shapes of words
In conflicts over beliefs and values, symbolic gestures matter more than reason or money

Reference: Kinzler, Dupoux & Spelke. 2007. The native language of social cognition. PNAS 104: 12577-12580

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Are women more talkative than men?

In 2006, a best-selling book claimed that women are over three times more talkative than men. But a new study, the first to actually measure how many words men and women say in natural conversations, has resigned this statistic to the urban myth bin.

In ‘The Female Brain’, author Louann Brizendine stated that women use about 20,000 words a day while men speak a mere 7,000. Predictably, the media loved the story and through widespread reporting, this statistic has almost reached the status of urban myth.

Women and men are just as chatty as each other.The success of Brizendine’s statistic as a meme is surely helped by the fact that it ‘sounds about right’, much like the infamous myth that Inuits have multiple words for snow. In this case, our stereotyped view of gender says that women are better at expressing themselves than men, who are content to grunt and repress their way through emotional experiences.

In the light of this common wisdom, Brizendine’s ‘fact’ seems like pointing out the obvious, and she helped matters along by providing a vague explanation.

As testosterone moulds the developing brain of male embryos, it slows the development of areas of the brain involved in emotion and communication. As adults, men pay the price for this and struggle to express themselves.

But scientists were not impressed. The journal Nature said that, “despite the author’s extensive academic credentials, The Female Brain disappointingly fails to meet even the most basic standards of scientific accuracy and balance.”

As it happens, Brizendine didn’t really have any data to go on. Until now, no studies have recorded the natural conversations of large groups of people over long periods of time, which means that the statistic in the book is a guess at best.

Evidence at last

For hard evidence, we can now turn to Matthias Mehl from the University of Arizona, and colleagues from the Universities of St Louis and Texas. They had a wealth of data to study. Over the past decade, they have been running experiments which involved unobtrusively recording natural conversations.

Their recorder is an electronic device, delightfully called the EAR (electronically activated recorder). The wearer keeps the EAR on for several days and every 12.5 minutes, it records a thirty-second snippet of sound. The researchers transcribe any conversations captured by the device, and use this to estimate the total number of words spoken throughout the day.

Men may have difficulty expressing themselves but that doesn’t mean that they’re any less talkative than women.Between 1998 and 2004, the group amassed recordings from over 210 women and 186 men. When they did a word count of the recordings, the results were very clear – both men and women use about 16,000 words a day.

Women used about 215 words more than average and men used 331 less, but this difference was not statistically significant. Neither gender was more verbose than the other.

Mehl admits that there are certain limitations to their data. For a start, all the people in the studies were university students between the ages of 17 and 29. It may be that larger differences would show up in people from lower educational background.

But not according to Brizendine’s theory – she suggested that women are more talkative because of fundamental biological differences that happen in the womb. If she was right, you wouldn’t expect these differences to be so completely masked in any socioeconomic group.

The final caveat is that only American and Mexican students were tested. In other countries, where gender equality is a much more troubling issue, there may be starker differences.

But in North America at least, women are not more talkative than men. Indeed, there may well be much larger differences between different men and women than there are between the two genders.

The moral of this story is that repeating a statistic doesn’t transform it into fact – we need experiments and good, hard data for that.

Reference: Mehl, Vazire, Esparza, Slatcher & Pennebaker. 2007. Are women really more talkative than men? Science

Related posts on gender issues and psychology:
Opinion: Women in science or “Why those at the top should mind what they say”
In conflicts over beliefs and values, symbolic gestures matter more than reason or money
Opinion: Discovery of ‘fat gene’ highlights stigma against obese people

In conflicts over beliefs and values, symbolic gestures matter more than reason or money

When battles are waged over values and ideologies, you can’t bribe or reason your way to peace. That’s the stark message from a new psychological study of people in the heart of the Israeli-Palestinian conflict.

Land - a solid resouce - can become a moral issue when prefixed by the word ‘holy’.The fight over the land of Israel/Palestine has raged for over a century and the peace process has been difficult, lengthy and often stagnant. All the while, lives continue to be lost in skirmishes and suicide attacks. Perhaps it’s time to put the situation under some scientific scrutiny.

A huge number of modern conflicts are fuelled by differences in opinions and beliefs, rather than grabs for power or land (at least on the ground level).

Even if the foundation of a dispute is not initially a moral issue, it can quickly become one. Land, for example, is a solid resource that can be completely transformed into something much more by adding the word ‘holy’ in front of it.

In these situations, people tend to forgo a rational weighing up of pros and cons in favour or making decisions with an intuitive moral compass. Jeremy Ginges and colleagues from the New School for Social Research studied the effects of this switch against the backdrop of the Israeli-Palestinian conflict.

Through a series of psychological experiments, they worked out that in these circumstances, the power of symbols is far greater than that of currency or logic.

They surveyed over 1,800 from three different groups: Jewish Israeli settlers, Palestinian refugees, and Palestinian students (half of whom were members of Hamas or related organisations).

Ginges asked the participants to consider hypothetical scenarios where they would have to compromise over issues that were particularly relevant to them. The Israeli settlers were asked about their willingness to exchange their land for peace, which would involved them having to relocate. The Palestinian refugees had to consider giving up their right to return to their former homelands. And the Palestinian students were asked to consider Palestine relinquishing sovereignty over Jerusalem.

Symbolic compromises are essential for engaging with moral absolutists.Unsurprisingly, all the participants were reluctant to compromise. But Ginges found that they fell into two camps based on the strength of their convictions.

The first, who he termed the ‘non-absolutists’ expressed no more than a strong preference against any compromises. The second group, the ‘moral-absolutists’, had elevated the respective issues to the status of sacred values and were more fervently against losing any ideological ground.

For example, about half of the Israeli settlers felt that the Jewish people should never cede part of the ‘Land of Israel’ not matter the cost or benefit. The other half opposed the loss of land but did not rule it out under extreme circumstances.

So far, so predictable. But the real surprise came when Ginges offered the participants the same compromise but with a rational incentive to sweeten the deal. The incentives included peace, resulting from the end of all hostilities, or money, in the form of substantial donations from the US or the European Union.

Faced with these added carrots, the two camps behaved very differently. The non-absolutists tended to take a pragmatic stance and softened their responses. After all, in rational terms, the extra benefits are better than nothing.

A Palestinian woman at MashaBut the moral-absolutists from both the Israeli and Palestinian sides showed even more outrage than before and an even greater number supported a violent response. For these people, bribes or appeals to reasons were just making things worse.

Symbolic incentives had the opposite effect. Moral-absolutists were more willing to compromise over their own sacred values if they saw that the other side was prepared to do the same.

For example, the Palestinian refugees were more prepared to recognise Israel’s right to exist if Israel would in return recognise the historic legitimacy of the refugees’ right to return. They were less angry about the thought of compromise and less supportive of violent responses or suicide attacks.

The swings in opinion were small but significant – elections in the Middle East have been settled by much smaller majorities.

It did not matter if these symbolic gestures altered the costs or benefits of the compromise, and indeed, in most cases they did not. It didn’t even seem to matter if the deals would be successfully carried out, and those surveyed were not confident that they would be.

The Israeli-Palestinian peace process is not amenable to reason or financial incentives.Amazingly, when you consider that this conflict regularly takes the lives of hundreds of people, it was the gesture that counted. It was the fact that one side showed willingness to even budge on matters of principle that prompted the other to do the same.

It just goes to show that when people promote their ideas to the rank of beliefs, they risk losing the ability to view those issues rationally.

Ginges has a reason for this. He believes we are almost programmed to avoid weighing things up in terms of costs and benefits when they concern our values or beliefs, preferring instead to rely on a moral compass. Indeed, we have such an inherent distaste for attempts to measure moral commitments in such a calculating way that such attempts are likely to be met by outrage and anger. So it was with the Israelis and Palestinians surveyed in this study.

In these situations, attempting to resolve the situations through logical arguments or financial bargaining can seriously backfire. Symbolic trade-offs hold much greater power in ensuring that peace can be achieved.

Reference: Ginges, Atran, Medin & Shikaki. 2007. Sacred bounds on rational resolution of violent political conflict. PNAS 104: 7357-7360.

Images: Photo of Palestinian woman and Israeli soldier by Justin McIntosh.

 

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Chimps have more adaptive genetic changes than humans

According to new research, chimpanzee genes have shown more adaptive changes than those of humans. The media widely reported the results as evidence that chimps are ‘more evolved’ than humans. But as I discuss here, these headlines are putting words into the researchers’ mouths.

Chimps have more adaptive genetic changes than humansSince the time when humans and chimps evolved from our common ancestor, our species appears to have come on by leaps and bounds. We walk on two legs, we speak using languages and while there is no doubt that chimps are intelligent, there is even less doubt that our brainpower outclasses theirs.

For years, scientists have assumed that our advanced abilities must be reflected in our genetics. After all, traits like intelligence and language give us great adaptive advantages. They should therefore be mirrored by similarly large changes in the human genome, compared to the chimp one.

Not so. Researchers at the University of Michigan sifted through the human and chimp genomes for signs of positive selection – the process where natural selection firmly embeds new mutations because of the advantages they provide. They found that the chimp genome contains 50% more positively-selected genes than the human one.

While earlier studies have compared individual human and chimp genes, this is the first to do a proper census. Margaret Bakewell and colleagues looked at almost 14,000 genes in both species.

The project was given a valuable push by the recent publication of the fully-sequenced rhesus macaque genome. The macaque – a type of monkey – is an evolutionary cousin of both humans and chimps, and provides a useful comparison.

Humans may have fewer adaptive changes than chimps because our population sizes have traditionally been smaller.If the team found a difference in the human and chimp genes, the macaque version can tell them which version is closest to the ancestral one. Previously, scientists had to make do with the mouse, a much more distantly related animal. The macaque’s presence gives the analysis greater accuracy.

Bakewell failed to find any noticeable differences in the function of positively-selected genes in humans and chimps. Both species even had similar proportions of positive changes among the genes that control the brain and nervous systems.

The reasons for this surprising result are unclear, but Bakewell feels that population sizes may hold the answer. For most of their evolution, chimpanzees have enjoyed a larger population size than humans have. It’s only recently that our numbers have ballooned to unfeasible proportions.

According to evolutionary theory, beneficial genetic changes are more quickly established in a population if it is larger. But in smaller groups, random genetic changes can trickle down through generations without being properly weeded out. This ‘genetic drift’ could explain why humans have fewer positively-selected genes than chimps do.

An alternative theory is that many of the human genetic changes that provide us with the greatest advantages may be relatively new developments. It is only recently in our history that we spread around the world from our origins in Africa, and as such, new genetic innovations may not have become established in the population as a whole.

A third theory, which I’m putting forward myself, is that the genetic changes responsible for our most human traits, may lie among stretches of DNA missed by this study. Recently, a study showed that one of the most important ‘genes’ in human evolution lies within our so-called junk DNA and controls the development of our brains. Clearly, we still have much to learn.

Evolution is not about progress.Nonetheless, the study helpfully shows that evolution is not necessarily about progress. It’s not an inexorable march toward some gleaming future. It’s about change, regardless of direction or result.

Somewhere along the line, the word ‘evolved’ started to gain a false value. It became an indicator of positive progress, so that claiming to be ‘more evolved’ than a peer is to claim superiority.

A huge number of newspapers and magazines reported this story under the headline of ‘Chimps more evolved than humans’. And while that may be technically reasonable, the inferences made were anything but.

The inherent values placed upon the phrase ‘more evolved’ clearly emerged in the reaction to the story. Some suggested that humans were obviously ‘less evolved’ given for reasons ranging from pollution to capitalism. Meanwhile, creationists and ID-supporters smelled blood in the water, and claimed that such as blatantly preposterous conclusion proved that evolution was nonsense.

Of course, no such conclusions were actually made by the study itself. In the light of the proper progress-free meaning of the word ‘evolution’, hese results are not preposterous, but fascinating. We should use them to drive a nail in the coffin of phrases like ‘evolutionary race’ or ‘more evolved’, at least in its value-laden non-scientific sense.

Reference: Bakewell, Shi & Zhang. 2007. More genes underwent positive selection in chimpanzee evolution than in human evolution. PNAS 104: 7489-7494.

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Discovery of ‘fat gene’ highlights stigma against obese people

On Friday, the media was abuzz with the discovery of a ‘gene for obesity’. Researchers funded by the Wellcome Trust found that people who carry a single copy of a variant of the FTO gene are 30% more likely to be obese than people with no copies.

People with two copies of the FTO gene are 70% more likely to be obese.But one in six Europeans carry two copies of this variant, and they are 70% more likely to be obese. On average, these dual carriers weighed three kilograms heavier than their peers.

The FTO gene itself is a mystery. Noone knows what it does or even which other genes it interacts with, and the Wellcome Trust team are now probably itching to find out.

But in this case, the reaction to the discovery was almost more interesting than the science itself. If internet talkbacks are any indication, people roughly fall into two groups.

To the first camp, the findings echo their own experiences of finding it difficult to maintain a healthy body weight. It points to something deeper and innate at work.

But the reactions from the other, slightly louder camp have been acrimonious to say the least. To them, the discovery of the FTO variant is yet another way for obese people to brush off the burden of responsibility from their shoulders.

After all, they say, obesity is just a matter of eating healthily and exercising regularly. To go beyond this is to over-complicate a simple lack of willpower. And where exactly was this gene in post-war Britain when obesity levels were much lower?

This attitude couldn’t be more wrong or more unhelpful, and many of these complaints misunderstand the nature of obesity-related genes.

Accusing obese people of being lazy or weak is inaccurate at best, stigamtising at worst.It is clear that obesity has some genetic basis, but no researcher worth their salt would imagine that a single gene dictates whether a person becomes obese or not.

Obesity-related genes are likely to work through much more delicate ways. Some may affect how we metabolise food or lay down fat. But subtlest of all are genes that affect our very behaviour.

These inherited influences could make individuals more responsive to the smells or sights of food. They could make the brain less responsive to signals from the gut that say, “I’m full.” They could give people a strong innate preference for the chemicals that give fatty foods their taste, or equally put them off the chemicals (often bitter ones) within healthier choices.

In a society where food supplies are modest, say post-war Britain, variations in such genes across a population wouldn’t have much effect. But in the 21st century, things are very different.

With more junk food widely available at cheaper cost, and active lives replaced by office jobs, cars and the telly, it is notoriously easy to eat lots and do little. In this environment, small genetic differences that affect how people react to food or activity can have massive effects.

So where was the FTO variant in post-war Britain? Well, in all likelihood, it was around, but its effects have been masked until now. Genes and environment interact with each other to affect our lives – nature and nurture usually walk hand in hand.

Obesity is caused by both genes and environmentObese people are likely to carry around a host of genetic variants that alter their behaviour in ways that leave them very vulnerable in a world where obesity is just around the corner. Obesity then, is a complex disease with many underlying causes.

And because of this, throwing words like ‘self-discipline’ and ‘laziness’ about with cavalier abandon does nothing for the obesity debate or for obese people themselves.

After all, where are personality traits like ‘discipline’ housed, if not the brain? And what controls behaviour and the development of the brain if not genetic information?

Is the combination of genes and environment an excuse for obesity? Hardly. But it does go some way toward explaining it, which is more than an accusation of faulty willpower will do.

Scientists hope that the discovery of genetic variants that influence the risk of obesity may one day herald new treatments for obesity. But this is a distant dream. For the present, very little actually changes for obese and overweight people.

To overcome the effects of genes and environment, they must still make lifestyle choices. The old maxim of “eat well, be active” still applies. The real benefit to FTO’s discovery would be a change in the attitudes of everyone else, from damning to supportive and from accusatory to understanding.

More on obesity:
A mismatch between nutrition before and after birth can lead to poor health
Human gut bacteria linked to obesity

Reference: Frayling, Timpson, Weedon, Zeggini et al. 2007. A common variant in the FTO gene is associated with body mass index and predisposes to childhood and adult obesity. Science 10.1126/science.1141634.

Image: Photographs by Boochan and Clarita

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