The history of life at hydrothermal vents

Abstract Hydrothermal vents are among the most fascinating environments that exist within the modern oceans, being home to highly productive communities of specially-adapted fauna, supported by chemical energy emanating from the Earth's subsurface. As hydrothermal vents have been a feature our planet since the Hadean, their history is intricately weaved into that of life on Earth. Despite an overall scant fossil record due to the improbabilities of preservation of vent deposits and organisms, recent fossil findings from ancient vent environments, accompanied by molecular data as well as fossils from ecologically-similar environments, have yielded invaluable new insights into the history of life at hydrothermal vents. Fossils from hydrothermal vents are among the earliest contenders for direct evidence of life on Earth, while a range of additional fossil finds indicate that vent habitats were readily exploited by microbes during the Precambrian. The first metazoans possibly appeared within vents during the Cambrian, and by the Ordovician-Silurian, hydrothermal vents in the deep ocean were colonised by mollusc, brachiopod and tubeworm taxa whose large abundances and sizes suggest these early animals were well-adapted to this setting. A transition in vent community composition occurred during the Mesozoic, as modern vent faunas began to occupy these environments and replace Paleozoic taxa. Molecular evidence indicates that many additional taxa radiated within vents during the Cenozoic, demonstrating that throughout Earth history, organisms were repeatedly able to overcome the challenges of adapting to the harsh conditions at vents to exploit their productivity. Targeting ancient vent deposits that have undergone low degrees of diagenetic or metamorphic change during mining-related exposure has great potential to provide further insights into the vent fossil record and fill existing gaps in knowledge.