Scientists have witnessed that bonobos adopt babies born outside of their social group for the first time in the wild.
Researchers, including psychologists at the University of Durham in the United Kingdom, have observed twice an unusual occurrence among bonobos in the Democratic Republic of the Congo, central Africa.
They say their findings give us greater insight into the parental instincts of a human being’s closest relative and could help explain the emotional reason why people so easily adopt children with whom they have no prior connection.
The research, led by Kyoto University in Japan, is published in the journal Scientific Reports.
Researchers observed a number of bonobo groups over several years in the Wumpa region of the Democratic Republic of the Congo.
Examples of cross-group adoption were seen between April 2019 and March 2020 before Covid-19 restrictions temporarily halted observations.
Qiu, who is between 52 and 57 years old, who is believed to be postmenopausal, was spotted adopting a three-year-old Ruby who was part of another unknown group.
Mary, 18, is also seen adopting Flora, who is estimated to be two and a half years old, after Flora’s mother disappeared from a separate group.
Chio or Marie, who already had no offspring, had no prior family ties to the adopted babies or any strong social ties with the biological mothers of the young, yet they both adopted baby bonobos.
Each of the adoptive mothers carried, nurtured and nursed the food and exchanged it with their adopted young. Both Ruby and Flora were also observed to be breastfeeding from their adoptive mothers. In Ruby’s case, she may have been breastfeeding for comfort since Chio is unlikely to produce milk.
The researchers say this caring nature is evidence of bonobos’ strong appeal to infants and the extreme tolerance of individuals, including immature young, outside their natural group.
Bonobos, along with chimpanzees, are humans’ closest relatives, and researchers say their discovery helps us understand adoption among people.
“Wildlife adoptive mothers are usually associated with orphaned infants or sometimes young women adopt orphans to improve their own caregiving delivery. Behaviors that increase the chances of their offspring surviving in the future,” said Mary Laurie Poart, PhD student in the Department of Psychology at Durham University, UK .
This means that adoption in non-human animals can usually be explained by the adoptive mother’s self-interest or pre-existing social relationships.
“The cross-group adoption that we have seen in the cases of Chio, Ruby, Marie and Flora is as surprising as it is wonderful and may help us explain human adoption, which cannot be explained solely by the benefits that adoptive mothers receive.
“Instead, it is fair to say from the examples we saw in bonobos that adoption in humans can be explained by selfless concern for others and the emotional desire to care for someone with whom we have no prior connection.”
Scientists have observed the bonobo groups included in this study since the 1970s, and researchers have identified the individuals in each group.
The lead author of the research, Nahoko Tokoyama, an associate professor at the Primate Research Institute and the Wildlife Research Center at Kyoto University in Japan, who has spent more than a decade studying bonobos in the Democratic Republic of the Congo, said bonobos “never stopped amazed.”
Dr. Tokoyama added: “Although adoptions have been observed in non-human primates, the adoptive mother and the adopters belong almost exclusively to the same social group.
“This may be because adoption is a very costly behavior and because non-human primates form stable groups and have a good ability to recognize other members of the group.
“It is known that groups of bonobos sometimes meet and cooperate with each other, and that those from different groups can interact with tolerance.
“However, I never imagined that bonobos could adopt children from outside their groups, so these cases were very surprising.”
The researchers plan to continue their observations of bonobos as soon as the Covid-19 restrictions allow.
The research, which also included the Environmental and Forest Research Center, Kinshasa, Democratic Republic of the Congo, was funded by the Japanese Association for the Promotion of Science, the European Research Council, the National Geographic Foundation for Science and Exploration, and the flagship program in Primatology and Wildlife Sciences at Kyoto University.