It might worry you that your ageing parents have pruned their social circle. Have most of their friends shuffled off this mortal coil or have they just become too grumpy and introverted to hang out with all the mates they had when they were younger?New research conducted in Germany shows that it is not just human beings who reduce their social circle in their twilight years and that it's perfectly natural.Julia Fischer, an academic at the Leibniz Institute for Primate Research in Göttingen, Germany, found that monkeys who are getting on in years do exactly the same.She and her team focused on free-roaming macaques in the south of France and discovered that those aged 25 years or older spent less than half as much time grooming other monkeys and also tended to half as many when compared with five-year-old adults.Fellow researcher Laura Almeling said that some theories suggest that human beings "become more socially selective when they know that their remaining lifetime is limited".However, she said "We assume that monkeys are not aware of their own limited future time" and this could, therefore, not explain their behaviour.Instead, she said, we should consider that "similar physiological changes" in both species make them more selective when older.Joy Walsh, 74, who stays in a retirement village in Johannesburg, said: "This makes sense to me. I like having a small group of friends. You've sort of grown old with these people and you know them and you are loyal to one another."I suspect all older people are like that. I have seen at my retirement village there is no visiting in big groups like when we were younger."For University of Cape Town researcher Jacqueline Bishop research into primates is a useful window into our own behaviour."When observing primates I am always reminded of how important individual personalities are in both the success and the breakdown of social groups. We can recognise the despot, the peacekeeper, the sulky adolescent, and research supports that these similarities between humans and primates are best explained by our shared ancestry," she said...