Microbial biomarkers reveal a hydrothermally active landscape at Olduvai Gorge at the dawn of the Acheulean, 1.7 Ma
Molecular fossil biomarkers illuminate a geothermally active oasis landscape at Olduvai Gorge 1.7 Ma at the emergence of the Acheulean technology. This study on the local paleolandscape reveals a mosaic ecosystem with great biodiversity, rivers, edible resources, and hydrothermal features. Evidence of hydrothermalism was found near sites intensively used by early hominins. The geothermal activity described here may have influenced the use of the space at Olduvai Gorge and may have provided advantages, such as cooking, which has not been previously contemplated in the context of human evolution.Landscape-scale reconstructions of ancient environments within the cradle of humanity may reveal insights into the relationship between early hominins and the changing resources around them. Many studies of Olduvai Gorge during Pliocene–Pleistocene times have revealed the presence of precession-driven wet–dry cycles atop a general aridification trend, though may underestimate the impact of local-scale conditions on early hominins, who likely experienced a varied and more dynamic landscape. Fossil lipid biomarkers from ancient plants and microbes encode information about their surroundings via their molecular structures and composition, and thus can shed light on past environments. Here, we employ fossil lipid biomarkers to study the paleolandscape at Olduvai Gorge at the emergence of the Acheulean technology, 1.7 Ma, through the Lower Augitic Sandstones layer. In the context of the expansion of savanna grasslands, our results represent a resource-rich mosaic ecosystem populated by groundwater-fed rivers, aquatic plants, angiosperm shrublands, and edible plants. Evidence of a geothermally active landscape is reported via an unusual biomarker distribution consistent with the presence of hydrothermal features seen today at Yellowstone National Park. The study of hydrothermalism in ancient settings and its impact on hominin evolution has not been addressed before, although the association of thermal springs in the proximity of archaeological sites documented here can also be found at other localities. The hydrothermal features and resources present at Olduvai Gorge may have allowed early hominins to thermally process edible plants and meat, supporting the possibility of a prefire stage of human evolution.All data pertaining to this study can be found in SI Appendix. GC-MS data have been deposited by Ainara Sistiaga at the Electronic Research Data Archive (ERDA) on 20 July 2020 (https://erda.ku.dk/public/archives/947e13a6272ba9d74056e7010319486f/publ...).
