Sibling rivalry, a near-universal experience for human families, isn’t limited to our species. New research published this week reveals that young chacma baboons in southern Africa exhibit strikingly similar patterns of jealousy and competition for maternal attention, offering a fascinating glimpse into the evolutionary roots of this complex emotion.
The study, conducted by researchers observing two troops of wild baboons in Namibia’s Tsaobis Nature Park between and , meticulously documented interactions between baboon mothers and their offspring. Researchers focused on instances where one infant would attempt to disrupt a mother’s grooming or resting time with another sibling, employing tactics ranging from gentle requests for affection to more assertive behaviors like biting, slapping, or vocalizing.
Axelle Delaunay, an evolutionary biologist at Finland’s University of Turku and lead author of the study, explained that jealousy is a “very striking” emotion in humans, but has been historically difficult to study in primates. “It’s been little studied among our fellow primates because jealousy is ‘very complicated to measure’,” she told reporters. The research team’s detailed observations, however, revealed behaviors that “strikingly mirrors patterns of sibling jealousy reported in humans.”
The findings challenge previous assumptions about sibling dynamics in primates. Traditionally, it was believed that limited instances of single births among primates meant there would be less competition between siblings. “Female primates usually only have one baby at a time, so ‘it was generally thought there was no real competition between siblings, because brothers and sisters are different ages and do not necessarily need their mother and her resources at the same time’,” Delaunay explained.
The study focused on 16 families within the two baboon troops, encompassing a total of 49 young siblings. Baboon societies are matriarchal, with power and resources typically passed down through the female line. Male baboons typically leave their natal troops after reaching puberty. Like human infants, baboon offspring experience a prolonged developmental period characterized by strong bonds with their mothers.
Researchers paid close attention to the mothers’ behavior, noting instances where they appeared to favor one infant over another during grooming sessions. This preferential treatment, a common dynamic in human families, seemed to trigger competitive responses from the less-favored siblings. The team meticulously recorded the frequency and nature of these interventions, providing a quantitative basis for their observations.
The study’s findings, published in Proceedings of the Royal Society B: Biological Sciences, suggest that the emotional underpinnings of sibling rivalry may be deeply ingrained in our evolutionary history. While the specific manifestations of jealousy may differ across species, the underlying drive to secure maternal attention and resources appears to be a common thread.
Interestingly, the research also indicated a developmental shift in baboon behavior. The study found that older baboons were less likely to interrupt their siblings’ time with their mothers, suggesting a growing understanding of social boundaries and resource allocation as they mature. This observation aligns with developmental psychology research on human children, where the intensity of sibling rivalry often diminishes with age.
The implications of this research extend beyond the realm of primate behavior. By demonstrating that jealousy and competition for maternal attention are present in another species, the study provides valuable insights into the evolutionary origins of these emotions in humans. It also highlights the importance of considering the complex social dynamics within animal families when studying their behavior.
The research team hopes to continue their work by exploring the long-term consequences of sibling rivalry in baboons, investigating how these early interactions shape their social relationships and reproductive success. Further studies could also examine the role of individual personality traits and environmental factors in influencing the intensity of sibling competition.
This discovery arrives alongside a renewed interest in animal cognition and emotion. Recent studies have demonstrated complex problem-solving skills in corvids, emotional responses to loss in elephants, and sophisticated communication abilities in cetaceans. The baboon study adds to this growing body of evidence, challenging the traditional view of animals as purely instinct-driven creatures and highlighting the rich emotional lives of our primate relatives.
