This paper expands upon the existing literature on the evolutionary importance of grandmothers by examining how direct care by grandmothers differs from care provided by other helpers within a population of Martu Aborigines. Behavioral observations were collected on ten babies who ranged from 3 months to 3 years of age. The results show that Martu grandmothers were in contact with their grandchildren more than any person other than the mother, and they were also more likely than any other category of caregiver to perform high-demand tasks, such as bathing or feeding. These results suggest that Martu grandmothers are specializing in the type of care they provide and posits that high-quality allocare is an important pathway to increased health and survival of grandchildren. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc.