Birth of a sibling triggers long-lasting stress in young bonobos

First-of-its-kind study identifies physiological changes in the transition to siblinghood. Young bonobos as old as eight years suffer long-lasting stress after the birth of a sibling. MPI of Animal Behavior/ Christian Ziegler - In any family, the birth of a child is a transformative event, often greeted with positive feelings from parents-and mixed feelings from siblings. The arrival of a new brother or sister, and the loss of parental attention that comes with it, is stressful for any first-born child. Now, scientists have shown that it is not just humans who have trouble becoming siblings. Bonobos, our closest living relatives, also experience stress in the transition to siblinghood. Following the birth of a sibling, young bonobos had five times higher levels of the stress hormone cortisol and a reduced immune response, which lingered for months.