The oldest record of modified steranes are in sedimentary rocks deposited ca. 720–820 million years ago. In contrast, diagenetic products of protosterols (called protostanes and cyclosteranes) are widely distributed in older Proterozoic rocks and imply the presence of extinct proto-eukaryotes and/or sterol-producing bacteria before the evolution of crown-group eukaryotes.
The earliest documentation of altered steranes is found in sedimentary rocks dating back approximately 720–820 million years. In contrast, the diagenetic byproducts of protosterols (known as protostanes and cyclosteranes) are widely present in older Proterozoic rocks, suggesting the existence of extinct proto-eukaryotes and/or sterol-producing microorganisms prior to the emergence of crown-group eukaryotes.