Oxygen and nitrogen occur in the form of different isotopes which vary in their proportions geospatially and climatically. Oxygen is absorbed into the body in the form of HO and is used in the growth of tissues. As with carbon, oxygen isotopic ratio variances can be attributed to specific locations and the proportion of O isotopes can therefore contribute to the reconstruction of past climates, understanding of diets and water consumption, seasonality, mobility patterns, life history and elements of culture.