Tetrahymanol is primarily used as a biomarker in geochemical studies to trace ancient microbial activity, especially in environments where anaerobic conditions prevailed. It is a stable compound that persists in sedimentary rocks over geological timescales, making it valuable for reconstructing past environmental conditions. Due to its origin from specific microorganisms like those found in freshwater or saline environments, its presence in rock samples helps scientists infer the type of ecosystem that existed millions of years ago. It is also used in organic geochemistry to assess thermal maturity of petroleum source rocks and to correlate hydrocarbon deposits. Its structural similarity to other pentacyclic triterpenoids allows comparison with related biomarkers to refine interpretations of depositional settings.