A larger view on tiny things: multi-proxy approaches for the understanding of Earth earliest fossils

The Precambrian Era constitutes the longest period of Earth history, spanning from the accretion of the planet (4.55 Billion years ago) to the rise of Animals (542 Million years ago). During this period, the massive changes in hydrosphere, atmosphere and geosphere influenced the development of the early biosphere. Conversely, the transition from prebiotic chemistry to life and the subsequent biological changes (complexification of cells; prokaryotic then eukaryotic photosynthesis, sexual reproduction, …) also played a role in modifying our young planet. Therefore, to be fully understood, the appearance and evolution of life on Earth (and elsewhere?) require multidisciplinary approaches intersecting, notably, biology, geology and chemistry.

In Precambrian, the fossil record mainly consists of organic-walled microfossil (OWM) preserved in sedimentary rocks. Despite an unclear biological origin for most of them, researchers have established sets of criteria and approaches to determine their probable biological lineages. By combining classical palaeontological investigations with spectroscopic and ultrastructural analyses, we were able to predict a fungal origin for one particular species of OWM. In addition, new synchrotron FTIR and XRF/XANES approaches on various Precambrian microfossils demonstrate the importance for more integrative studies of early life traces.