Hydrogen hypothesis
The Hydrogen hypothesis is a model proposed by William F. Martin and Miklós Müller in 1998 that describes a possible way in which the mitochondrion arose as an endosymbiont within a prokaryotic host in the archaea, giving rise to a symbiotic association of two cells from which the first eukaryotic cell could have arisen (symbiogenesis). According to the hydrogen hypothesis: The hosts that acquired the mitochondria were hydrogen-dependent archaea, possibly similar in physiology to modern methanogenic archaea, which use hydrogen and carbon dioxide to produce methane; The future mitochondrion was a facultatively anaerobic eubacterium which produced hydrogen and carbon dioxide as byproducts of anaerobic respiration; A symbiotic relationship between the two started, based on the host's hydrogen dependence (anaerobic syntrophy).