Yawns, hiccups, prune fingers - we wouldn't be here without them Prune fingers may once have been vital, according to Dr Smulders's research. He asked 20 volunteers to move marbles from one hand to another and into a underwater box. Those with wrinkly fingers were 12 per cent faster than those without. His research is supported by pictures that show Japanese macaques develop wrinkly fingers when they sit in hot springs, suggesting fellow mammals may have acquired the feature for the same purpose. So what other traits persist? Goosebumps have no purpose in the modern world, but serve as a reminder of a more brutal era when, under threat, we would make our hair stand on end to appear larger. Scientists are also examining whether goosebumps are an indicator of dishonesty, appearing when we tell lies. Yawning also appears pointless today, but it could have been developed to enable primates to monitor air quality in enclosed spaces or, because the act is so contagious, to encourage humans to empathise with and learn from one another, according to Dr Matthew Mason, a physiologist at Cambridge University. Some traits, such as hiccuping, have been retained as side-effects of more beneficial processes. As Dr Mason explains: "It can be an inevitable if unwanted consequence of something else, which is advantageous and selected for, and you can't lose one without the other." In the case of hiccups, a reflex to keep the digestive tract working functions too well, causing a "fit" even when there is no problem: "It may not achieve anything very useful, but it is a consequence of having some useful reflexes that help dislodge food and sometimes go wrong," says Dr Mason. Some of our most common evolutionary "relics" can cause pain. Not only can appendicitis lead to life-threatening infections, but the appendix has been "useless for a good hundred thousand years," according to Dr Robin Allaby of Warwick University. So why have we not lost the small, worm-like appendage attached to the colon? "It is generally not a problem," says Dr Allaby, "so there is no selection pressure." Other scientists have suggested it might act as a reservoir of good bacteria, helping to repopulate the gut. Its original purpose is better understood. "It is a throwback to our time of chewing hard plant matter," says Dr Allaby. You will see rabbits have a well-developed appendix where you will have a colony of bacteria that will be good at breaking down things such as cellulose. Similarly, the coccyx - or human tail bone - can be very painful if broken. "It will hurt like hell," Dr Allaby says. Despite this, it is predominantly harmless and was very helpful when our ancestors used their tails for balance. There is, though, good news for those who suffer from one painful throwback: wisdom teeth. They were useful hundreds of thousands of years ago for chewing tough plant matter, but today only lead to visits to the dentist. "The third molars are in a state of flux," says Dr Allaby. They will be selected against. They could be gone very, very rapidly. Well, within tens of thousands of years.