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.

Continue reading

Brain of the beholder – the neuroscience of beauty in sculpture

Blogging on Peer-Reviewed ResearchIs beauty simply in the eye of the beholder, or do all the beholders’ brains have something in common? Is there an objective side to beauty? Plato certainly seemed to think so. His view was that beauty was an inherent property that all beautiful objects possess, irrespective of whether someone likes it or not.

Brain of the beholder – the neuroscience of beauty in sculptureTo him, beauty in the world stemmed from an ideal version of Beauty that real objects can only aspire to. A biologist might instead suggest that the objective side of beauty stems from built-in predispositions for certain features, colours, shapes or proportions.

The opposing view is that art is a fully subjective enterprise and our preferences are shaped by our values and experiences. The real answer is likely to lie somewhere in the middle – after all, art students learn basic common skills such as proportion, perspective and symmetry before embarking on their own stylistic journeys.

Artists, critics and gallery visitors can argue about this question all they like, but some clearer answers have now emerged from three researchers in Italy, arguably the home of the some of the world’s most beautiful art. Cinzia Di Dio, Emiliano Macaluso and Giacomo Rizzolatti from the University of Parma have brought the tools of the modern neuroscientist into the debate.

Continue reading

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.

Continue reading

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

Technorati Tags: , , , , , , , , ,

Cultured chimps pass on new traditions between groups

Chimpanzee groups have their own cultural traditions. Now, scientists have shown that chimp groups can transmit new behaviours to each other, by seeding new behaviours into a group and watching them spread.

For humans, our culture is a massive part of our identity, from the way we dress, speak and cook, to the social norms that govern how we interact with our peers. Our culture stems from our ability to pick up new behaviours through imitation, and we are so innately good at this that we often take it for granted.

Chimpanzee groups can learn new traditions from each other.We now know that chimpanzees have a similar ability, and like us, different groups have their own distinct cultures and traditions.

Now, Andrew Whiten from the University of St Andrews has published the first evidence that groups of chimpanzees can pick up new traditions from each other. In an experimental game of Chinese whispers, he seeded new behaviours in one group and saw that they readily spread to others.

Chimp cultures

Many animals have their own cultural traditions. Songbirds, for example, copy their parents’ melodies, and small variations lead to groups with different dialects. But chimpanzees have by far the richest cultures so far observed.

These scope of their culture first came to light in 1999, when Whiten, together with Jane Goodall and others, carefully documented at least 39 cultural behaviours among wild chimpanzees. Many of these were a matter of course in some populations, but completely absent in others.

Some groups use sticks to extract honey, others use them to retrieve marrow from bones, and yet others use them to fish for ants. Some get attention by rapping their knuckles on a branch, while others noisily rip leaves between their teeth. Some groups even have a rain dance.

Whiten has previously published three studies which demonstrated different sides of chimp cultural transmission. The first showed that trained individuals can spread seeded behaviours within a group. The second showed that cultures trickle through the generations as parents teach their children new behaviours. And the third showed that arbitrary conventions such as gestures and displays can spread as easily as skills involving tool use.

Now, together with an international team of researchers from the University of Texas and Yerkes National Primate Research Center, including primate expert Frans de Waal, Whiten has produced the first experimental evidence that cultural transmission can happen between different groups.

Seeding behaviours in groups

Whiten worked with six groups of captive chimps, each consisting of 8-11 individuals. They lived in large but separate enclosures arranged in two rows of three and each group could observe its neighbours, but not interact with them.

Whiten trained one chimp from groups one and four to solve two difficult tasks – the ‘probe task’ and the ‘turn-ip’ task – in order to get some food hidden inside a box. Each chimp was taught to use a different technique.

The probe taskIn the probe task, the chimp could move a lever at the top of the box to open a hatch, and use a stick to impale the food (A). Alternatively, it could use another lever at the side to lift an opening, giving it enough room to manoeuvre a stick inside and push the food out (B).

The turn-ip taskIn the turn-ip task (C), food items were dropped down a pipe, where they were blocked by a disc. The disc had a hole in it, that would allow the food to fall through when it was properly aligned. The chimps could turn the disc either by rotating an exposed edge or using a ratchet. Once the food dropped through, the chimps could get at it by pressing or sliding one of two different handles.

Group transmission

Once the student chimps had mastered their new methods, they were returned to their respective compounds and the whole group was allowed to try its hand at the tasks. Before the training, none of the chimps managed to successfully get at the food. But after just one chimp was taught the technique, most of the others in the group quickly picked it up.

The boxes were then moved to a different position, where chimps from the second pair of groups could watch chimps from the first pair solving the task. After a time, it was moved to another position where the third pair of groups could watch the second one.

Whiten found that the techniques were accurately and quickly transmitted between the different chimpanzee groups. His experiment clearly shows that chimps have an immense capacity for learning new behaviours from their peers. They do this accurately and different groups can acquire and maintain several varied cultural traditions.

Different chimpanzee groups have distinct cultural traditions.In light of this evidence, the regional behaviour patterns seen in chimp groups across Africa are, without a doubt, the result of cultural transmission. In the wild, rival groups are often hostile towards each other and it is unlikely that chimps sit down in jungle conferences to share new ideas. But females do move between groups and Whiten believes that they carry new cultural traditions with them.

How exactly the new behaviours spread is still a matter for debate. Some scientists have suggested that the chimps learn by ‘emulation’, meaning that they focus on the results of actions rather than the actions themselves. But other studies found that chimps don’t respond to ‘ghost’ lessons, where task machinery is operated by remote and not by another chimp.

The most likely explanation is that chimps imitate the actions of other chimps and are very good at learning from each other. In all likelihood, the common ancestor that we share with chimps had the same ability, and also had strong cultural streams running through its populations.

Find out more: If you’re interested in chimp intelligence and evolution, have a look at some of my previous posts on chimp gestures and the evolution of language, the chimp Stone Age and the evolution of tool use, and their use of tools for hunting.

Reference: Whiten, Spiteri, Horner, Bonnie, Lambeth, Schapiro & de Waal. 2007. Transmission of multiple traditions within and between chimpanzee groups. Current Biology 17: 1-6.

Images: Image of experimental apparatus taken from Cell Press.

Technorati Tags: , , , , , , ,

Loss of traditional knowledge in the Amazon leads to poorer child health

In the heart of Bolivia, an Amazonian society is losing its traditional knowledge of the medicinal value of local plants, to the detriment of its children’s health.

The Tsimane’ are a small seven thousand-strong population, living in a lowland region of Bolivia, who possess tremendous knowledge about the plants they share their forest with.

The Tsimane’ rely on their knowledge of local plants to survive.Their botanical know-how trickles down through the generations and allows them to use the local plant-life for construction, tool-making, medicine and food.

These plants account for over half of their household consumption of goods, while those purchased from the outside world make up a meagre three per cent at most.

But globalisation is changing all that. The Tsimane’ are now starting to integrate into societies that place no value on their indigenous knowledge. They are promised alternatives in the form of Western medicine without necessarily having access to it. Their culture is disappearing.

But unlike many other societies, it is only beginning to do so. And that gives scientists like Thomas McDade and William Leonard from Northwestern University a chance to work out what impact the loss of traditional knowledge might have on the Tsimane’s future.

To do this, they assessed the health of 330 Tsimane’ children, aged 2-10, and tested their mothers and fathers on both their knowledge about local plants and their skills at using them.

Tsimane’ children have worse health if their parents are less botanically savvyTheir results were striking. Children with plant-savvy parents – mothers in particular – were much healthier than their peers, irrespective of other factors such as education or integration into other societies.

Those the other hand, those with more ignorant parents had higher levels of an immune system chemical called C-reactive protein, that accumulates in the presence of frequent infections. They had smaller fat reserves to draw on for growth of fighting off disease. And they were more likely to have stunted growth, a sign of infections or malnutrition.

Westerners often look down on traditional knowledge as mere folk tales or cultural curios. But for the Tsimane’, they are clearly more – they are a vital ingredient for the society’s good health. Knowledgeable mothers can pick out the most nutritious plants to give their children the healthiest and most balanced diets (and all without Jamie Oliver’s assistance).

But various forest plants also have medicinal value. In an environment rife with disease and with little access to modern medicines, the Tsimane’s knowledge acts as a buffer against infections, helping their children to recover faster.

And since parents begin passing their tips and tricks down at an early age, children of well-versed parents can start self-medicating or helping their younger friends.

The cultural transmission of knowledge is a key part of the human species’ adaptive power. And as globalisation continues for better or worse, we would do well to remember that such enlightenment also exists at a small and intimate scale.

Education, modern medicine and economic security can certainly boost global prosperity. But as the Tsimane’ show, they can also do harm at a local level by replacing vital cultural expertise while offering little in its place.

Not all ‘traditional knowledge’ is necessarily worth considering…On the other hand, it would be foolish to assume that all ‘traditional knowledge’ is golden.

The strength of Western medicine lies in it scientific foundations and its own transmission of knowledge through journals and conferences. Groups like the Tsimane’ arrive at their local knowledge of plants through remarkably parallel means, using similar processed of inductive reasoning.

But there, the impetus is survival. Their knowledge of local plants is put to constant use and there is great value in getting things right. Using the wrong plant in the wrong circumstances could make things much worse, and there is a strong incentive for weeding out incorrect strategies. Superstition doesn’t get a look in.

When the stakes are lowered, the door is open to quackery. A herb salesman on a busy high street, for example, may claim that their prescriptions may claim to be based on centuries-old knowledge but face no direct repercussions if their products don’t work.

Without the immediacy of need that the Tsimane’ face, knowledge handed down over generations can be diluted to the point of inaccuracy.


Reference: McDade, Reyes-Garcia, Blackinton, Tanner, Huanca & Leonard. 2006. Ethnobotanical knowledge is associated with indices of child health in the Bolivian Amazon. PNAS 104: 6134-6139.

Images: All images from Tsimane’ Amazonian Panel Study (TAPS) website

Technorati Tags: , , , , ,

Opinion: Not so unique – the chimpanzee Stone Age, and our place among intelligent animals

This is the 50th article for this blog. I’ve been writing for it for over six months now, and I pleasantly surprised that I’m still finding the enthusiasm to write for it regularly, and that people seem to be reading it.

This special article considers new evidence for the origins of chimpanzee tool use. It is the third piece of research I’ve seen in the last few months which shows that other animals share an ability previously thought to be the sole province of humans. In this article, I consider why these discoveries are now coming to light, and what they mean for us.

In the Ivory Coast, a small stream called Audrenisrou winds its way through the lowland rainforest of the Tai National Park. On the floodplain of this stream, at a site called Nuolo, lie several stones that seem unassuming at first glance. But to the trained eye, they are a window to the past.

Chimps are advanced tool users, and have been for some timeTheir shape is different to other stones that have been worn away by natural erosion. They have been flaked in systematic ways and many are flattened and sharp. Clearly, they were shaped by hand for a purpose – they are tools.

Their creators were not humans, but close relatives who lived in these rainforests thousands of years ago – the ancestors of modern chimpanzees.

Nuolo: humans or chimps?

The Nuolo stones were uncovered by Julio Mercader form the University of Calgary, Christophe Boesch from the Max Planck Institute of Evolutionary Anthropology, and their colleagues. They are a magnificent archaeological find – the first ever evidence of prehistoric ape behaviour anywhere in the world.

Humans have a rich prehistoric past, informed by key archaeological finds like the Olduwan sites. These findings provide us with a window into the past, showing us how our ancestors developed the tools that continue to serve us well today. For chimps, no such sites have been found, until now.

Julio Mercador at the Nuolo excavationThe evidence that the Nuolo specimens were created by chimps is compelling. The density of stone pieces in the site, the preferred types of rocks, the length of the stone flakes and the patterns of wear closely mirror those of modern chimp tools.

They also carry the evidence of their past uses, as hammers and anvils for cracking nuts. Their crevices contain granules of starch that clearly came from nuts. Mercador and Boesch even managed to narrow the granules’ origins down to three possible species, all of which are currently cracked and eaten by today’s chimps. In contrast, the team found scant remains of tubers and legumes, the main food source of forest-dwelling humans.

This suggests that prehistoric humans who also, over time, visited the river-side site were not the creators of the Nuolo tools. But Mercador and Boesch found even stronger evidence.

Human hammers usually weight less than 400g, and even our ancestors’ anvils weighed no more than a kilogram. The far more powerful chimp with its larger hand can wield a tool many times heavier, anywhere from one to nine kilograms in weight.

Mercador and Boesch found that the stone tools at Nuolo most likely weighed about 2 kilograms, far too heavy heavier for a human but well within the limits of even a weak chimpanzee.

A chimpanzee Stone Age

A chimp cracks a nut with a stone hammerTogether, this evidence paints a remarkable picture of a chimpanzee Stone Age, when ancient chimps were clearly cracking nuts in the same way they do now, over four millennia ago.

Chimpanzees are highly advanced tool users. But some critics have sold short their abilities, claiming that they learned the use of tools by, for lack of a better word, apeing nearby humans.

The Nuolo finds puts paid to that suggestion. The tools predated the advent of farming in the rainforest by some time. Nuolo also lacks evidence of any of the other tools used by humans to grind and pound starchy tubers.

Among chimpanzees, nut-cracking is clearly a cultural tradition, passed down over time through over 200 generations of chimps. Humans and chimps either developed this technology independently, or they inherited it from a common ancestor who had already begun to use tools.

We’re not so unique after all

With studies like this, the list of attributes that are unique to humans seems to be getting smaller all the time. In just the last few months, scientists have found that chimpanzees hunt with spears, jays (below) can plan for the future, and even the long-dead dinosaur Bambiraptor, gripped prey with opposable fingers.

The beautiful western scrub-jay - a bird that can plan for the future.But as we start to come down from our pedestal, we should not mourn the loss of our position, but rejoice in our connectedness with the rest of the living world. These discoveries emphasise our position at the end of a continuous evolutionary spectrum, rather than atop a looming precipice.

The outdated view that we have been awarded special dominion over other life should be replaced by a humbler view, where our position of biological authority is tempered with respect.

Why has it taken so long for such findings to come to light? Centuries ago, anthropomorphism was commonplace and these experiments would have seemed like pointing out the obvious. But of late, biology has taken a more reductionist turn and signs of potential animal behaviour are scrutinised under the harshest and most sceptical light.

In many cases, this quite rightly avoids the false conclusions based on flimsy and anecdotal evidence. But while scientists have taken great care to ensure that their interpretations are not biased towards human perspectives, the same cannot always be said the design of the experiments themselves.

Looking for intelligence

One of the most significant problems with studying animal intelligence is that many species experience and react to the world in completely different ways to us. For example, to pass the classic test for self-awareness, an animal must show that it recognises itself in a mirror, by examining a mark previously made on its face (see right).

elephants-paper32.jpgGorillas and dogs tend to fail the mirror test, but not because they are mentally less advanced than successful examinees like elephants or chimps. Gorillas view direct eye contact is a sign of aggression and tend to avoid it, while dogs rely on smell as their primary sense, rather than sight.

Simply put, can we truly claim to understand the limits of another animal’s intelligence when we know so comparatively little about their behaviour or perceptions? Cleverly designed experiments may bring us closer to an answer, but sadly, we may never get the opportunity to conduct them.

800px-bottlenose_dolphin_ks.jpgSave ourselves, the most intelligent animals on the planet – the great apes, elephants, dolphins and whales – are mostly endangered, with many species facing a very real threat of extinction. Chimpanzees, like those in the Tai National Park are under threat from the loss of their habitat, and the illegal bushmeat trade.

A massive amount of evidence now paints these, our closest cousins, as sophisticated animals with their own culture. Imagine how tragic it would be if they died out for good, leaving only a set of shaped stones as the only lasting signs of their intelligence.

Reference: Mercader, Barton, Gillespie, Harris, Kuhn, Tyler & Boesch. 2007. 4,300-Year-old chimpanzee sites and the origins of percussive stone technology. PNAS 104: 3043-3048.

Technorati Tags: , , , , ,