Does running explain the naked ape?
15 September 2011
Compared with other mammals of similar size, humans are odd-looking creatures because they lack body hair and stand upright. This difference has puzzled zoologists for decades, and speaking at the British Ecological Society's Annual Meeting earlier this week, LJMU’s Dr David Wilkinson explained how better computer models are shedding light on this contentious issue.
According to Dr Wilkinson, who illustrated his talk with pictures of the near naked combatants in David's Intervention of the Sabine Women and the statue of Adam, clad only in a fig leaf, in Milan Cathedral: “Most major western art galleries contain paintings or sculptures of the human nude, yet viewed through the eyes of a zoologist rather than an art lover these representations show remarkably odd animals that have lost their body hair and walk upright.”
One of the most important explanations of why we look so odd was proposed by LJMU’s Dean of Science, Professor Peter Wheeler. In a series of seminal papers published in the 1980s and early 1990s based on mathematical models, he suggested our lack of hair and upright stance were adaptations that helped early humans keep cool on a hot African savanna.
Performed before powerful computers were widely available, Professor Wheeler's calculations – which were done on a programmable electronic calculator – could not take into account the impact of running on early humans' thermal ecology. Humans are adept at endurance running but exercise produces internal heat, a major issue for active animals in hot environments.
One influential theory proposed after Wheeler's work suggests that endurance running, used to run animal prey into the ground, played an important role in our evolution. This theory is, however, contentious, so Dr Wilkinson and Professor Graeme Ruxton of the University of Glasgow used new data and more powerful computers to revisit Wheeler's model – with intriguing results.
Dr Wilkinson says.
"In earlier models our virtual ancestors stood still in a gentle breeze, but our new model allows them to run around. This means we can investigate the theory that human body shape is an adaptation which allowed our ancestors to run for long distances in hot conditions.”
The model shows endurance running requires high rates of sweating and areas of hairless skin similar to modern humans. "Our model suggests that although the earliest upright humans may well have walked from place to place or run short distances – perhaps to a tree to escape predators – they could not run long distances to catch their supper. Humans are unusually sweaty mammals and our results show just how important sweating rates are in allowing long-distance running in the tropics,"he explains.
The meeting will also learn what the new model reveals about why we walk upright and have lost most of our body hair. "The model predictions suggest to us that upright stance probably evolved not to keep us cool, but for other reasons," says Dr Wilkinson. "In my view, Wheeler's ideas still provide one of the most plausible explanations for why we lost most of our body hair, but I am more sceptical about his explanations for why we started walking upright. Without the ecological pressures of hot African habitats during our evolution modern artists might today be drawing much hairier life models."
Dr David Wilkinson, Reader in Environmental Science at the School of Natural Sciences and Psychology, presented his full findings on 13 September 2011 to the British Ecological Society’s Annual Meeting at the University of Sheffield.
The story was featured internationally by the press which in the UK included The Daily Telegraph and coverage on The Daily Mail website: http://www.dailymail.co.uk/sciencetech/article-2036740/Hair-Why-lost-locks-run-faster-catch-food.html
The paper containing the results on endurance running is Graeme D Ruxton and David M Wilkinson (2011), “Thermoregulation and endurance running in extinct hominins: Wheeler’s models revisited”, Journal of Human Evolution, 61, 169-175, doi: 10.1016/j.jhevol.2011.02.012.
The British Ecological Society is a learned society, a registered charity and a company limited by guarantee. Established in 1913 by academics to promote and foster the study of ecology in its widest sense, the Society has 4,000 members in the UK and abroad. Further information is available at www.britishecologicalsociety.org