A Story of Ants, Ageing and Altruism

From The Independent by Steve Connor.

King Solomon is said to have told sluggards to look to the hard-working ant and be wise. Aesop, too, extolled the virtues of the humble ant in his fable explaining why the insect's constant toiling through the summer months would make for an easier winter compared with the fortunes of the lazy, singing grasshopper.

Now there is another reason to admire the tiny, colonial denizens of the insect world. Ants not only work hard and are prepared to lay down their lives for their fellow ants, they also take bigger risks for the good of the colony as they get older – and they can even assess how much time they have left in life.

It is well established that worker ants tend to take greater risks as they get older. Scientists have shown that this behavioural trait benefits the colony because certain risky activities, such as foraging far from the nest, are best done by ants coming to the end of their useful lives – it doesn't pay to put young workers in high-risk jobs.

One remaining question, however, was whether ants had some internal mechanism that told them how old they were and how much time they had left before dying.

Dr Moron believed that it might be possible to manipulate an ant's lifespan artificially, and to observe changes to its risk-taking behaviour as a result. His study, published in the latest issue of the journal Animal Behaviour, did just this by increasing the concentration of carbon dioxide in a chamber housing an ant's nest. High concentrations of carbon dioxide increase the acidity of the blood and curtail an ant's lifespan.

As the scientists predicted, the worker ants in the colony began to forage further afield earlier than they would have done if they had been brought up in a low carbon dioxide atmosphere. The findings are further evidence of the apparent altruism of the ant. These workers are not only prepared to sacrifice their lives to serve and protect their queen, they also have the ability to make careful calculations of just how much risk they should take based on their current life expectancy.

Many different kinds of animals, other than ants, are known to be altruistic and the issue of how this could evolve in a world of selfish genes remained unresolved until about 40 years ago with the work of the late William Hamilton of Oxford University. It was Hamilton who showed that the altruism seen in ants and other social insects could be explained by something called kin selection.

But would the altruism of the simple ant explain human altruism? Most people show the greatest kindness to their own children, followed by the children of their closest relatives. It cannot explain the more conscious acts of true altruism that people often show to complete strangers. Human altruism may be far more complex, but the humble ant has at least given us a hint of how our own unselfish behaviour first evolved.


Ants Plug Holes to Smooth Journey.


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