Early evolution of large micro‐organisms with cytological complexity revealed by microanalyses of 3.4 Ga organic‐walled microfossils

Abstract

The Strelley Pool Formation (SPF) is widely distributed in the East Pilbara Terrane (EPT) of the Pilbara Craton, Western Australia, and represents a Paleoarchean shallow-water to subaerial environment. It was deposited ~3.4 billion years ago and displays well-documented carbonate stromatolites. Diverse putative microfossils (SPF microfossils) were recently reported from several localities in the East Strelley, Panorama, Warralong, and Goldsworthy greenstone belts. Thus, the SPF provides unparalleled opportunities to gain insights into a shallow-water to subaerial ecosystem on the early Earth. Our new micro- to nanoscale ultrastructural and microchemical studies of the SPF microfossils show that large (20-70 μm) lenticular organic-walled flanged microfossils retain their structural integrity, morphology, and chain-like arrangements after acid (HF-HCl) extraction (palynology). Scanning and transmitted electron microscopy of extracted microfossils revealed that the central lenticular body is either alveolar or hollow, and the wall is continuous with the surrounding smooth to reticulated discoidal flange. These features demonstrate the evolution of large micro-organisms able to form an acid-resistant recalcitrant envelope or cell wall with complex morphology and to form colonial chains in the Paleoarchean era. This study provides evidence of the evolution of very early and remarkable biological innovations, well before the presumed late emergence of complex cells.

An Akouemma hemisphaeria Organic Macrofossils Colony Hosting Biodiversity Assemblage on the Seafloor of Okondja Basin (Gabon) dated at 2.2 Ga

“…This process likely corresponds to a division phase, recalling the vegetative reproduction of unicellular micro-organisms [58,59] or primitive macro-organisms [60] including the enigmatic macrofossils of late Ediacaran [61].…”

Growth, Duplication and Lateral Mutual Compressive Deformation of Akouemma hemisphaeria on the Seafloor of Okondja Basin at 2.2 Ga (Gabon)

“…Similarly, the fission process recalls the cell division of microorganisms such as algae [22], protozoa [23] and Archean micro-organism [24], or the duplication of primitive metazoans as enigmatic macrofossils of late Ediacaran [25], Echinoderm Holothuria (sea cucumbers) [ …”

The longevity of habitable planets and the development of intelligent life

“…Instead we consider the 3.2 − 3.4 Gyr cases documented by Javaux et al (2010), Wacey et al (2011), Sugitani et al (2015, and the 2.5 Gyr samples from Czaja (2016). These studies were all published in the last few years, indicating the rapid development of the field.…”