SIGNAL TO NOISE: UNRAVELING BIOLOGICAL INFORMATION FROM PRESERVATIONAL OVERPRINTS IN EXCEPTIONAL FOSSILS

Our current understanding of the early evolution of complex life is provided largely by the fossil record of soft-tissues, which is unfortunately rife with biases and distortion. The information provided by fossil soft-tissues can be likened to a signal-to-noise ratio; that is, in each case of soft-tissue preservation, true biological information represents the “signal”, and artificial features arising from selective information loss through decay or addition from mineral overprinting represents the “noise”. In many cases, the presence and extent of signal-corrupting noise is not easy to recognize, and can result in conflicting interpretations of the same fossil material. A prime example of this may be seen in our earliest potential animal fossils, the 600 Ma Doushantuo embryos, for which several radically different phylogenetic interpretations have been proposed. These fossils are not alone in controversy, and many other representatives of early life, both single-celled and multicellular, have faced similar challenges. These complications are fortunately not codas to the story provided by soft-tissue fossils, but to interpret it correctly and fully, that is to “turn up the signal, wipe out the noise” (Gabriel, 2002), requires that we develop a thorough understanding of how the soft-tissue record was written. To this end, we must critically analyze soft-tissue fossils from a chemical perspective and pragmatically interpret their taphonomic histories in an effort to determine which aspects reflect original biological signal, and therefore have evolutionary significance, and which reflect the noise imparted by post-mortem decay, chemical alteration, and inorganic mineralization. As an overview, this presentation will emphasize three case studies, two of which focus on resolving the nature and origin of nucleus-like structures in Ediacaran Doushantuo embryos and Paleoproterozoic Ruyang acritarchs, and the third spotlighting fossils described as macroalgae from the Cambrian Wheeler Shale of Utah. Utilizing combined analytical approaches, centering on scanning electron microscopic techniques, microtaphonomic research provides a means to decipher and disentangle biology from taphonomy and holds valuable potential for shedding light on evolutionarily significant intervals in Earth’s history.