Evidence for motility in 3.4 Gyr-old organic-walled microfossils ?

Abstract

The oldest traces for planktonic lifestyle have been reported in ca. 3.4 billion years old silicified sediments from the Strelley Pool Formation in Western Australia. Observation of flange appendages suggests that Archean life motility was passive and driven by drifting of microorganisms in their surrounding environment. Until now, the oldest traces for active motility are ca. 2.1 billion years old. Whether or not active motility already existed during the Archean eon remains an open question. Here we report the discovery of new 3.4 billion years old tailed microfossils. These microfossils exhibit a lash-like appendage that likely provided them with movement capabilities. This suggests that these microfossils are the oldest remains of active motile life forms. With the ability to move in liquids and on organic and/or mineral surfaces, these microorganisms were capable of escaping from harsh environments and/or colonizing new ecological niches as early as 3.4 billion years ago. The existence of these deep-rooted Archean motile life forms offers a new picture of the Archean biodiversity, with unanticipated evolutionary innovative morphological complexities.