Few species develop as slowly as humans, both in terms of developing adult skills and brain development. Human infants are born so underdeveloped that they cannot survive without adult care and feeding for some years after birth. Children still need to learn fundamental skills such as walking, eating, talking, using tools and much more. The timing of these developmental milestones is used by doctors to determine if a child and the child's brain are developing normally. However, we know little about the timing of motor and social developmental milestones in other long-lived, closely related species such as chimpanzees, nor what they indicate for brain development. For example, when do chimpanzees start to walk, feed themselves, groom others and use tools? Fully charting development milestones in wild chimpanzees and other species can shed light on the evolutionary basis of such extended developmental periods.