New research has shown that happier orang-utans live longer which may shed light on the evolution of happiness in humans. Dr. Alexander Weiss and colleagues at the University of Edinburgh and the University of Arizona, who are presenting their paper published in Royal Society journal Biology Letters at the Society for Experimental Biology Annual Conference in Glasgow on Sunday the 3rd of July, used an innovative approach to assessing happiness by asking keepers who work with orang-utans to answer questions on the animals' behalf.

The keepers were asked how often the orang-utan was in a good mood as opposed to a bad mood, how much it enjoyed social interactions and whether it was effective at achieving its goals. The keepers were also asked to speculate as to how happy they would be if they were the animal in question.

Of the 184 orang-utans included in the study those which were scored as happier by their keepers were significantly more likely to be alive up to seven years later. The effect remained even when factors such as sex, age and species were taken into account.

The Evolution of Happiness
These results could shed light on how happiness evolved, not just in orang-utans but all primates, including ourselves. Dr. Weiss says "Already we have shown that certain personality traits linked to happiness share the same genetic basis in humans and chimpanzees. Studying these relationships across a wide range of species could yield fascinating insights into the evolutionary bases of happiness, depression and a host of other psychological characteristics that impact the lives of humans and, most likely, a range of other species."

One theory of how happiness evolved is sexual selection; a happier individual might be more attractive to the opposite sex because they are likely to live longer, and vice versa. Dr. Weiss suggests that in the future other researchers might look to dating websites for information, to discover whether the profiles of individuals who rate themselves as happier are more popular.

Although happiness has been linked to longer life in humans, and now orang-utans, the basis for this is not well-understood. Dr. Weiss says: "It is unlikely that happiness causes longer life, the association is almost certainly more complex." The next step for scientists in understanding the importance of happiness in the lives of orang-utans will be to assess whether happiness and health are governed by the same genes.

Animal Welfare Applications
This research also shows that the insight of orang-utan keepers should be taken seriously as it can give vital information on the animal's well being.

Using simple questions like those in the current study would provide an efficient, low cost method of assessing the well being of orang-utans in zoos all over the world. Monitoring orang-utan health and well being in this way will help, says Dr Weiss "to ensure that orang-utans too live 'happily ever after'"