I have been thinking a great deal about happiness and how we can best study the happiness of our species. That is why a recent study on great ape mood caught my eye. I found it quite insightful. The study was led by psychologist Alexander Weiss, who investigated patterns of well-being in two great ape species: chimpanzees and orangutans (Coles, 2012). In this study, Weiss and his colleagues wanted to understand if our closest relatives share the same general life pattern of well-being that humans seem to possess. Social scientists have established that humans experience a U-shaped pattern of well-being. This means that as a species we tend to experience greatest mental health in youth, become far less happy throughout midlife, and then become happier again in old age (Weiss et al., 2012). This seems to be a general pattern regardless of various socio-cultural and economic factors. The study by Weiss et al. (2012) provides some evidence that this U-shaped well-being curve is an evolved predisposition that we share with our closest relatives.
In the study, 508 captive great apes of varying age ranges were rated based on their ‘happiness’. However, happiness is notoriously difficult to study. Many social scientists are still struggling to understand how to study happiness in humans. Researchers decided that the best way to study happiness in apes was to survey the people who knew them best: their keepers. In the survey happiness was rated using four criteria (Callaway, 2012):
- The animal’s overall mood
- How much pleasure they got out of socializing
- Their success in achieving goals such as obtaining food and objects they desire
- How happy the keeper would be if s/he were that animal for a week
The results of this survey indicated that individuals in their late 20s to mid-30s were significantly less happy than individuals younger and older (Weiss et al. 2012). These results mirror the U-shaped happiness curve found in humans and raises some interesting questions about the evolutionary pressures that would have selected for these patterns.
Admittedly, the study is intensely anthropomorphic. As primatologist Frans de Waal suggested, it would have been nice to see a harder measure of ape happiness (e.g., stress hormone levels) (Callaway, 2012). Furthermore, I do think future studies should incorporate a more sophisticated methodology over a longer period of time before we can conclude with certainty that great apes experience a U-shaped well-being curve. However, I think this study does give us some insight into our own happiness, because it is relatively easy for keepers to gauge the mood of the apes they know so well. Also, the fact that the data enabled such strong conclusions that parallel our own pattern indicates that this may be a study worth replicating in the future.
So, if you trust the methodology, what does this tell us about the evolutionary pressures that produced it? Do these results mean that we are all destined to experience a mid-life crisis to some degree, regardless of socio-economic status and/or our own personal perception of age-appropriate achievement?
I believe that if a U-shaped curve is something we share with our closest relatives then it has probably been present for tens of millions of years throughout ape evolution and potentially primate evolution. It is plausible to suggest that the main pressure for this U-shaped curve would be the need for increased adaptability during mid-life. Generally speaking, young and old individuals are under less pressure to accumulate resources for survival and do not have the added burden of needing to increase biological fitness. Perhaps being discontent increases the likelihood that an individual will put extra effort into acquiring more resources or finding a new/better mate. It would make sense that there would be a strong selection pressure for this throughout our evolution because resources were so scarce and difficult to acquire. Discontented middle-aged individuals would likely be able to out compete (and out survive) those middle-aged individuals that were content. Of course, if this is true we need to test whether discontentedness is adaptive.
Either way, future research regarding great ape happiness needs to be conducted before we can be sure that the U-shaped curve is something they share with humans. If future data indicate it is true, our only chance of minimizing the bottom of the U-shaped curve may be to genetically reprogram ourselves.
Callaway, E. 2012. Great ape go through mid-life crisis. Nature. Accessed November 21, 2012. http://www.nature.com/news/great-apes-go-through-mid-life-crisis-1.11847
Coles, J. 2012. Great apes may have ‘mid-life crisis’, a study suggests. BBC Nature. Accessed November 21, 2012. http://www.bbc.co.uk/nature/20359229
Weiss, A. et al. 2012. Evidence for a mid-life crisis in great apes consistent with the U-shaped in human well-being. Proceedings of the National Academy of Sciences. doi: 10.1073/pnas.1212592109