The fit between the geochemistry of alkaline vents and the biochemistry of methanogens and acetogens is so close that the word analogous does not do it justice. Analogy implies similarity, which is potentially only superficial. In fact, the similarity here is so close that it might better be seen as true homology – one form physically gave rise to the other. So geochemistry gives rise to biochemistry in a seamless transition from the inorganic to the organic.
