Great apes such as chimpanzees and orangutans may have more in common with our species than we previously thought. Other than a similar genetic makeup, the apes also exhibit similar social tendencies, including, it seems, going through a midlife crisis.
The evidence is published in the Proceedings of the National Academy of Sciences of the United States of America under the title "Evidence for a midlife crisis in great apes consistent with the U-shape in human well-being."
The U-shape curve refers to the happiness curve humans go through. We seem to be happiest in our youth, with a dip occurring midlife, and an upward rise in happiness as we enter old age. Chimpanzees and orangutans seem to go through the same trend.
"The reasons for this U-shape are still unclear. Present theories emphasize sociological and economic forces. In this study we show that a similar U-shape exists in 508 great apes (two samples of chimpanzees and one sample of orangutans) whose well-being was assessed by raters familiar with the individual apes," reads the study abstract.
The raters all had to have worked with each ape for a minimum of at least two years and they asked the apes to go through a short happiness questionnaire based on a human model.
"You don't have the chimpanzee hitting midlife and suddenly they want a bright red sports car," said lead author of the study Dr. Alexander Weiss. "But there may be other things that they want like mating with more females or gaining access to more resources."
The scientists are hoping that this behavioral similarity will allow for them to better understand social tendencies in humans. It may even explain the origins of the midlife crisis, which Dr. Weiss believes is merely a motivational kick from nature.
"Our results imply that human well-being's curved shape is not uniquely human and that, although it may be partly explained by aspects of human life and society, its origins may lie partly in the biology we share with great apes," the study abstract stated.