Maintaining participation beyond the initial period of engagement is critical for peer production systems. Theory suggests that an increase in motivation is expected with contributors' movement from the community periphery to the core. Less is known, however, about how specific motivations change over time. We fill this gap by focusing on individual motivational paths in the formative periods of engagement, exploring which motivations change and how. We collected data on various instrumental and noninstrumental motivations at two points in study participants' Wikipedia career: when they started editing and again after six months. We found that non-instrumental motivations (including collective and intrinsic motives) decreased significantly over time, in contrast with socially-driven motivations such as norm-oriented motivates which did not change and social motives which increased marginally. The findings offer new insights into newcomers' evolving motivations, with implications for designing and managing peer-production systems.