Grandmothers play a key role as alloparents in human families. A leading hypothesis suggests that the inclusive fitness benefits of grandmaternal care selected for an extended female lifespan after reproduction, a unique trait among primates. Beyond lifespan extension, grandmothers may have biological adaptations for caregiving. Research from our lab shows grandmothers have lower DNA methylation of the oxytocin receptor gene (OXTR) compared to non-grandmothers, with lower methylation linked to stronger bonds with grandchildren. MRI scans reveal grandmothers have a lower brain age than controls, further reduced among those with higher engagement. These findings suggest grandmotherhood may enhance oxytocin signaling, promoting bonding and slowing brain aging. Recorded on 02/14/2025. (#40383)