Prader-Willi syndrome (PWS) is caused by a lack of expression of paternally-expressed imprinted genes at human chromosome 15q11-13 and is characterized by a switch from infant anorexia to childhood hyperphagia. A recent multiphase staging system recognizes gradual changes between the anorexic and hyperphagic phases of PWS. We undertook to use clinical records from an independent population to assess the multiphase system and explore the implications for the evolution of distinctive features of human childhood. Medical records of 258 clinic visits by 55 patients with PWS were reviewed with a focus on appetite and feeding. These clinical records were found to be inadequate for placing patients into particular phases of the multiphase system. Under the multiphase system, the onset of hyperphagia in PWS appears to coincide more with the timing of adrenarche than weaning from the breast and this timing should frame future evolutionary hypotheses. We discuss challenges encountered while attempting to use clinical data to explore evolutionary questions, but also identify useful information contained in the records.