Physiological markers are valuable tools to investigate the emergence and progression of life stages during life. The changes in levels of physiological markers, e.g., hormone levels, can be used to investigate the timing and expression of specific developmental events, to compare temporal patterns of life-history within and across species. Developmental changes in morphology and behaviour are accompanied by increased or decreased activity of hormone axes. Hormonal changes triggered by these axes have been related to events such as juvenile pause, menarche, and aging. Products of the somatotropin axis are related to growth spurts. Many of these physiological markers have been measured predominantly in human serum samples, whereas studies of wild-living animals are comprised almost exclusively of non-invasively collected samples of urine and faeces. Physiological markers measured in non-invasive samples from bonobos can be used to investigate specific patterns during ontogeny including adrenarche, juvenile pause, gonadarche, and somatic growth spurts. These studies provide standardized developmental profiles in a variety of species allowing to elucidate phylogenetic patterns as well as life history trade-offs.