New insights into a hot environment for early life

Summary Investigating the physical‐chemical setting of early life is a challenging task. In this contribution, the author attempted to introduce a provocative concept from cosmology – cosmic microwave background (CMB), which is the residual thermal radiation from a hot early Universe – to the field. For this purpose, the author revisited a recently deduced biomarker, the 1,6‐anhydro bond of sugars in bacteria. In vitro, the 1,6‐anhydro bond of sugars reflects and captures residual thermal radiation in thermochemical processes and therefore is somewhat analogous to CMB. In vivo, the formation process of the 1,6‐anhydro bond of sugars on the peptidoglycan of prokaryotic cell wall is parallel to in vitro processes, suggesting that the 1,6‐anhydro bond is an ideal CMB‐like analogue that suggests a hot setting for early life. The CMB‐like 1,6‐anhydro bond is involved in the life cycle of viruses and the metabolism of eukaryotes, underlying this notion. From a novel perspective, the application of the concept of the CMB to microbial ecology may give new insights into a hot environment, such as hydrothermal vents, supporting early life and providing hypotheses to test in molecular palaeontology.