Abstract : The oxygen isotope compositions of bones (n = 11) and teeth (n = 20) from 12 Sudanese individuals buried on Sai Island (Nubia) were analysed to investigate the registration of the evolution of the Nile environment from 3700 to 500 years BP and the potential effects of ontogeny on the oxygen isotope ratios. The isotopic compositions were converted into the composition of drinking water, ultimately originating from the Nile. δ(18)O values decrease during ontogeny; this is mainly related to breastfeeding and physiology. Those of neonates present very large variations. Neonates have a very high bone turnover and are thus able to record seasonal δ(18)O variations of the Nile waters. These variations followed a pattern very similar to the present one. Nile δ(18)O values increased from 1.4 to 4.4 ‰ (Vienna Standard Mean Ocean Water) from the Classic Kerma (∼3500 BP) through the Christian period (∼1000 BP), traducing a progressive drying of Northeast Africa.