Jim Vaupel was one-of-a-kind. His personality, style and demeanor were not designed to make scientific contributions at the fifth decimal place. He was after big game and he roamed widely in search of it, drew large numbers into the search parties, and employed many different weapons in the capture.

His favorite weapon was mathematics, which offered the most precision and closure. He developed a series of fundamental equations describing population dynamics. Rather than assuming that all members of a population had the same demographic characteristics, he introduced variability into these relationships. No modern student of demography is unfamiliar with Jim’s demonstration of how population heterogeneity must affect the age-pattern of mortality.

The age-pattern of mortality was a focal point of Jim’s research. He resisted the idea that there was a maximum length of the human lifespan—I think that it was inconsistent with his inherent optimism. Many of his empirical studies showed powerfully the plasticity of mortality at older ages and the regularity of its progress. Studies of other species that he initiated with collaborators from biology found examples of species whose mortality patterns did not reveal an aging process at all.

Jim’s contributions to demography are not limited to his own research but extend to the large number of students and professionals for whom he served as teacher and mentor. He was kind and generous to those at an early and vulnerable career stage, as well as to those who were more accomplished. Above all, he offered to everyone a wonderful example of enthusiasm and energy in pursuit of the abundant gifts that science can offer.