Paper wasps – caring mothers evolved into selfless workers

The workers of many social insect colonies give up their chance to reproduce in order to raise their sisters and their nieces. A new genetic study in paper wasps, which are halfway down the road to this extreme altruism, tells us that worker selflessness evolved from motherly care.

Imagine that one day, you make a pact with your brother or sister, vowing to never have children of your own and instead spend your life raising theirs. You’ll agree to do the grocery shopping, cook for them, clean their rooms and bathe them, until you die.

A paper wasp foundress begins the task of building a hive.That seems like a crazy plan, but it’s one that some of the most successful animals in the world – the social insects – have adopted. It’s called ‘eusociality’ and it’s a puzzle for evolutionary biologists. Why should an animal forgo the chance to reproduce in order to help rear its siblings and their young?

The strategy makes sense if you share enough genes with your close relatives. In helping them, you indirectly ensure the transmission of your own genetic material. But even if this explains the existence of eusociality, it doesn’t explain how such an extreme form of co-operation evolved.

Now, Amy Toth and colleages at the University of Illinois have found a clue in the genes of the paper wasp, Polistes metricus, which suggests that their altruistic actions evolved from motherly behaviour.

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Altruistic chimpanzees clearly help each other out

Many scientists have argued that only humans show true altruistic behaviour. But a group of Ugandan chimps is set to change all that by showing clear signs of true selflessness, helping other unrelated chimps with no desire for reward.

Why do we help each other, instead of constantly looking out for ourselves? This is one of the most compelling questions in modern biology. Evolutionary and game theory alike predict that selfish behaviour should be the rule with altruism the exception, and animal experiments have largely supported this idea.

Nature, ‘red in tooth and claw’, is painted as a fierce competition between selfish individuals and their even more selfish genes. In this stark landscape, true altruism is a rare quality and some scientists believe that it’s one that only we humans possess.

Even our closest relatives, chimpanzees, are not exempt from this dividing line. Certainly, there is a large amount of anecdotal evidence of chimps helping each other or even saving each others’ lives. But some thinkers believe that this behaviour, along with other seemingly selfless animal acts, is actually self-serving in one of two ways.

The chimps could be helping their relatives in order to advanced the spread of its own genes, which family members are likely to share. Or they could be doing a favour for another individual, in the knowledge that it will be repaid later on. Either way, it’s the do-gooder that eventually benefits.

Humans, on the other hand, seem to flaunt this rule. We often help others who are not relatives and who are unlikely to repay the favour. We go out of our way to be helpful, and sometimes even risk personal harm to do so.

Two tests for altruism

Now, Felix Warneken and colleagues form the Max Planck Institute for Evolutionary Anthropology have found compelling evidence that we are not alone. Contrary to previous studies, they have found that chimps also behave altruistically in a very human way. They help out unrelated strangers without expectation of reward, and even go to great lengths to do so.

Warneken studied 36 chimps at Ngamba Island Chimpanzee Sanctuary, Uganda and looked at their willingness to help a human handler. To minimise the effect of any human-chimp bond, he only looked at chimps that were born in the wild, and used experimenters who the chimps had never seen before.

In the first test, the chimps saw a human unsuccessfully trying to reach a stick that they themselves could reach. Warneken found that chimps were all too happy to pass the stick across (video), regardless of whether they were rewarded with a banana or not. In fact, the only thing that affected their readiness to lend a hand was whether the human was struggling for the stick or just passively staring at it.

He found the same thing when he ran a similar set-up with a 36 eighteen-month-old human toddlers, but with toy cubes in lieu of sticks (video). At that age, a baby’s mental abilities are thought to similar to those of chimps, and indeed the only real difference between the two was that the babies were quicker with their assistance.

Passing a stick across is obviously fairly easy but would altruism persist if there was effort involved? Warneken tested this by changing the experiment so that the chimps had to climb over a raceway (video) and the toddlers had to walk past a series of obstacles (video). Those that helped in the first test were happy to do so in the second, again without any rewards.

The third and most important test

A skeptic might argue that this doesn’t show anything. During their stay at the sanctuary, the chimps could have learned that helping any one of their strange two-legged keepers was worth it. The acid test then, was to see if the chimps would help each other.

The first chimp – the subject – could only get into a room with food by lifting the chain attached to its door. But it couldn’t reach the chain – only a second chimp, the observer, could do that. And once again, the chimps proved their selflessness, lifting the chain for their fellow chimps the vast majority of the time (video).

This striking result flies in the face of other studies, which have failed to find altruistic behaviour between chimps. But in a related commentary, Frans de Waal, an international expert of ape behaviour, claimed that these were more tests of generosity than selfishness.

They created specific situations where chimps were motivated to look out for themselves and the species can’t be judged on these scenarios alone. It would be like claiming that all people are selfish after watching the self-interested behaviour of commuters. Failing to show altruism is not the same as proving that it doesn’t happen.

But it does happen – Warneken’s experiments are striking indicators of that. In the third test, the chimps were unrelated, the observer had no chance of getting a share of the food, and their roles were never reversed so there were no opportunities for payback. Clearly, humans are not alone in our desire to help each other. Chimps are now our fellows in altruism and it’s likely that our common ancestor did the same.

What this means for the altruism debate

It’s particularly fascinating that rewards in the first two tests didn’t affect the chimps’ behaviour. This suggests that chimps don’t continually analyse the pros and cons of helping their fellow – if they did, the reward would have motivated them to help even more often.

Instead, de Waal believes that the chimps have evolved psychological systems that steer them towards selflessness. In essence, natural selection has done the analysis for them and decided that altruistic behaviour works to its advantage in the long run. Selfless behaviour then, can evolve for selfish reasons, and that strikes to the very core of the debate on altruism.

Spend enough time reading about this field of research, and you could be forgiven for thinking that some scientists are taking cynical glee at ‘explaining away’ altruism. The extreme reductionist view is that discovering the evolutionary origins of selfless behaviour discredits that behaviour, somehow making it less worthy. As Robert Trivers put it, these models are designed to “take the altruism out of altruism”.

But this viewpoint is blinkered and too focused on the past. Evolutionary explanations can help us understand where an unusual behaviour like selflessness comes from, but they do not alter the value of those behaviours. They can tell us about how a behaviour arose, but not about an animal’s reasons for behaving in that way here and now.

Take sex. Its adaptive benefits are clear – it continues the line and promotes genetic diversity. But animals don’t consider the issue of reproduction every time they have sex and for the most part, humans actively deny it!

According to de Waal, we should now turn our attention to the psychological processes that foster altruism in chimps, and how they are different from those that work in our own minds. Do chimps share our strong sense of empathy, that fuels selflessness by letting us identify with the emotions and needs of others. Do their cultures, like ours, punish and vilify selfish behaviour?

References: Warneken, Hare, Melis, Hanus & Tomasello. 2007. Spontaneous altruism by chimpanzees and young children. PLOS Biology 5: e184.
de Waal. 2007. With a little help from a friend. PLOS Biology 5: e190.

Related posts on chimps:
Chimps show that actions spoke louder than words in language evolution
Not so unique – the chimpanzee Stone Age, and our place among intelligent animals
Cultured chimps pass on new traditions between groups
Chimpanzees make spears to hunt bushbabies

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Army ants plug potholes with their own bodies

Images: from BBC, Nature, Jane Goodall Institute and Ngamba Sanctuary

Army ants plug potholes with their own bodies

Army ants are wonderful examples of animal co-operation. In one species, workers use their own bodies to fill potholes in the paths of their sisters, leading to easier journeys and more food for the colony.

Imagine that you’re driving along a country lane. As often happens, the road suddenly transforms from a well-paved street to a pothole-ridden nightmare. As your suspension and your stomachs start to tire, your friends in the back suddenly force you to stop the car.

To your amazement, they jump out and lie across the potholes, beckoning you to drive your car over them. It may seem like a far-fetched scenario, but if you were an army ant, such selfless behaviour would be a matter of course.

An army ant worker plugging a pothole.Army ants are some of the deadliest hunters of South America. Amassing in legions of over 200,000 ants, they become a massive predatory super-organism that fan out across the jungle floor leaving dismembered prey in their wake.

Behind the killing front, the corpses of the ant’s prey are taken back to the nest by foragers. But the route back home is not a smooth one. At an ant’s size, small twigs and leaves can be the equivalent of a bumpy, unpaved motorway.

Scott Powell and Nigel Franks from the University of Bristol found that at least one species of army ant (Eciton burchellii) solves this problem with living paving. Certain workers stretch their bodies over gaps in the forest floor, allowing their food-carrying sisters to march over them.

Eciton burchellii, a deadly predator, but a highly co-operative one.The ants carefully size-match to the holes that they plug. Powell and Franks stuck planks with different sizes of hole in the path of the ant column, and found perfect matches between ant and hole.

By smoothing the trail home, they ensure that other workers can return food to the colony as fast as possible. Powell and Franks calculated that this increase speed means that the colony as a whole gets more to eat, even thought the plugging ants cannot carry any food themselves.

It may seem that the plugging ants have a hard lot in life. But they are ultimately rewarded for their temporary sacrifices. When the foraging trip finally ends, the pluggers can look forward to a hearty meal when they return home. By taking on a specialised role, these ants improve the performance of the colony as a whole.

Reference: Powell & Franks. 2007. How a few help all: living pothole plugs speed prey delivery in the army ant Eciton burchellii. Animal Behaviour doi:10.1016/j.anbehav.2006.11.005

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How Big Brother keeps us honest

Even selfish people can act selflessly when their reputation is on the line. Now, a simple experiment reveals just how honest people become when they feel that Big Brother is watching them.

The wallet problem - would you take it if you thought someone was watching?Imagine that you’re walking along a quiet street and you see a wallet lying on the pavement. Would you take it? Now imagine the same situation with a small difference – the wallet has a red circle drawn around it. While many people would be tempted in the first scenario, almost no one would touch the wallet in the second.

The key difference is that the lone wallet was most likely dropped accidentally by a passer-by. But the encircled wallet was clearly placed and marked by someone, who may well still be watching. And there is nothing that keeps people more honest than the presence of a watchman.

Explaining honesty

Social experiments like these are of great interest to biologists because they tell us more about the nature of selfishness and altruism. In recent years, selfishness has become something of a biological buzzword and many influential writers have cast living things as self-serving vessels acting for the benefit of their genes. In this harsh light, individuals co-operate with each other only if they reap a personal reward.

But some acts of altruism, particularly human ones, are harder to explain. We are often kind and generous to others, even if they are unrelated (and so share no genes) or are unlikely to ever repay the good deed. Is this true selflessness, or is there something else going on?

Image is everything

One theory is that such selfless acts do provide benefits – they raise the reputation of the do-gooder in the eyes of their peers. Some lab experiments have supported this idea by showing that people co-operate more strongly if they know they are being watched.

Now, Melissa Bateson and colleagues at the University of Newcastle have shown just how strong this effect with a cunning psychological experiment. Rather than study subjects in an artificial environment, they chose to run a simple test on the other unwitting members of their university’s Division of Psychology in their own coffee room.

The walls have eyes

For years, Bateson had put up a friendly notice reminding staff members to pay for their tea, milk and coffee by putting money into an honesty box. To run her experiment, she made one small change – she added an image banner to the top of the notice which alternated on different weeks between some flowers and a pair of eyes.

Being watched makes people more honestEach time, different eyes were used of varying gender and expression but in all cases, they were staring straight at the reader. When she compared the amount of money collected from week to week, with the amount of drink that people bought, the results were striking.

On average, people paid almost three times more for their drinks when the pair of eyes watched over them. When the image changed from flowers to eyes, the payments always went up and when they were changed back, they always went down. The mere appearance of Big Brother prompted people towards greater heights of honesty.

Being watched

It’s very unlikely that the eyes made the staff members consciously believe that they were actually being watched. After all, the room’s layout ensured that cheats who didn’t pay up would never be caught by their colleagues.

Instead, Bateson believes that the eye images probably set off unconscious and automatic reactions in people who viewed them, a sort of mental reflex. Her theory is that our brains are very keenly attuned to cues that indicate that their behaviour could affect their reputation.

The presence of onlookers could be one such cue, and indeed, human brains have special neurons that are primed to respond to eyes and faces. The effect of such cues must be very strong indeed, since the relatively weak stimulus of an image of eyes produced such strong changes in behaviour.

Being human

But what does this say about us? Are we truly all self-serving hypocrites, helping each other solely to further our status? Clearly not. For a start, even the images of flowers prompted staff members to contribute small amounts of money to the honesty box. If we were all the wholly selfish creatures that reductionists might have us believe, then even these paltry payments might be unexpected.

But more importantly, the responses to the eye images were sub-conscious, rather than active decisions. A selfless act consciously designed to further one’s status might be robbed of its valour. But a selfless act based on an instinctive reaction is a selfless act nonetheless.

If this experiment tells us anything, it is that safeguarding our reputation, for whatever reason, is very much part of being human.

Reference: Bateson, Nettle and Roberts. 2006. Biol. Lett. 2: 1744-9561.

Related posts on morality:
Our sense of fair play lives on the right side of the brain
The Lady Macbeth effect – how physical cleanliness affects moral cleanliness

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In conflicts over beliefs and values, symbolic gestures matter more than reason or money
Why music sounds right – the hidden tones in our own speech
Impulsive brains are primed for drug addiction