Archaea: “Consistent with their status as a third form of life, archaea exhibit certain characteristics of bacteria, certain characteristics of eukaryotes, and some characteristics unique to themselves. They also span a broad range of biological properties, and many of them are specifically adapted to extreme environmental conditions.” — ScienceDirect
Subsurface habitats on Earth host an extensive extant biosphere and likely provided one of Earth’s earliest microbial habitats. Although the site of life’s emergence continues to be debated, evidence of early life provides insights into its early evolution and metabolic affinity. Here, we present the discovery of exceptionally well-preserved, ~3.42-billion-year-old putative filamentous microfossils that inhabited a paleo-subseafloor hydrothermal vein system of the Barberton greenstone belt in South Africa. The filaments colonized the walls of conduits created by low-temperature hydrothermal fluid. Combined with their morphological and chemical characteristics as investigated over a range of scales, they can be considered the oldest methanogens and/or methanotrophs that thrived in an ultramafic volcanic substrate.Cellular remains in a ~3.42-billion-year-old subseafloor hydrothermal environment By Barbara Cavalazzi, Et Al Science Advances14 Jul 2021 : EABF3963 Oldest microfossils with methane-based metabolism in a subsurface environment expand the frontiers of early Earth habitability.
Life seems to have got started as soon as the planet cooled.
The more we learn, the more interesting it becomes:
The newly identified fossil threads have a carbon-based shell. That shell is different structurally from the preserved interior, suggesting a cell envelope enclosing the cells’ insides, the authors write. And the team found relatively high nickel concentrations in the filaments. The concentrations were similar to levels found in modern methane-makers, suggesting the fossils’ metal may come from nickel-containing enzymes in the microbes.Carolyn Wilke, “3.42-billion-year-old fossil threads may be the oldest known archaea microbes” at ScienceNews (July 26, 2021)
It’s interesting to note that we didn’t even know archaea existed until Carl Woese and coworkers discovered them in 1977.
Curiously, unlike bacteria, Archaea do not cause disease in humans.
And, since we are here anyway, Woese was not a Darwinist.