Sibling rivalry is often seen as a very human problem but new research suggests it may have much deeper evolutionary roots.
A study of wild baboons in Namibia has found that young baboons frequently interrupt their mother’s interactions with siblings in ways that closely resemble jealousy-driven behaviour seen in human children.
The research, published in Proceedings of the Royal Society B, focused on chacma baboons living freely in the wild. Researchers observed mother baboons grooming their offspring–a key social and bonding behaviour–and recorded how other siblings reacted when they were not the focus of attention.
The results revealed a consistent pattern: young baboons were much more likely to interfere when their mother was grooming another sibling than when she was available and not interacting with anyone.
According to the authors, “offspring were more likely to interfere when their mother was engaged in a grooming bout with a sibling than when she was socially available.”
This finding suggests that the interruptions were not simply attempts to seek attention. Instead, they appeared to be reactions to seeing a sibling receive exclusive maternal care.
One of the most striking findings was what these interruptions actually achieved. In most cases, the interfering baboon did not gain grooming or attention from the mother. Instead, the interference often caused the grooming session to stop altogether.
In other words, the behaviour was more about breaking up the interaction than benefiting directly from it. The study reports that “interferers were twice as likely to disrupt mother–sibling grooming bouts than to obtain maternal or sibling grooming.”
This pattern mirrors behaviour observed in young children, who may interrupt a parent’s interaction with a sibling even when doing so does not result in extra attention for themselves.
The study also found that interference was not random. Young baboons were more likely to interrupt when the sibling being groomed was younger, of the same sex, or received more grooming overall from the mother. These “favoured” siblings appeared to attract more interference, suggesting that baboons are sensitive to differences in how maternal attention is distributed.
This sensitivity to unequal treatment closely resembles findings from human psychology, where children who perceive a sibling as favoured often show more conflict and rivalry.
Age played a major role in how often baboons interfered. Younger individuals were the most frequent interrupters, while older offspring were much less likely to do so. As baboons grow and become more independent, maternal attention becomes less critical for their survival and social success.
This decline over time fits with what researchers know about human development, where jealousy and rivalry tend to lessen as children mature and gain emotional regulation skills.
The researchers stress that they cannot directly measure emotions in animals. Feelings like jealousy are internal mental states, and behaviour alone cannot prove what an animal is experiencing. However, when similar behaviours occur in similar social situations across species, emotional explanations become harder to dismiss.
As the authors note, “sibling interference in chacma baboons strikingly mirrors patterns of sibling jealousy reported in humans.”
Rather than claiming baboons experience jealousy exactly as humans do, the study suggests that jealousy-like emotional mechanisms may be evolutionarily ancient and shared across closely related species.