Chronic stress could be one reason why some animal orphans have shorter lives and less offspring. Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig and the Institute of Cognitive Sciences, CNRS in Lyon assessed if, as orphan humans, orphan chimpanzees are exposed to chronic stress. They found that maternal loss is stressful but orphans experience little chronic stress since stress hormones return to normal after two years, possibly thanks to care provided by other chimpanzees.