ONE remarkable discovery of recent decades is the presence of hundreds of unusual species, including fourteen new families, at hydrothermal vents, These animals, unknown from other habitats, live in extreme chemical and thermal conditions around vents on spreading centres of the mid-ocean ridges and back-are basins. Chemosynthesis provides an in situ energy source for the thriving vent fauna. This habitat has existed through the Phanerozoic(1,2) and probably since the Archaean, thus providing sites for long-term adaptation. We now test the hypothesis that animal distribution among hydrothermal vents is related to tectonic plate history(3,4). The predominant migration pathway is most likely to occur along mid-ocean ridges rather than by shortest oceanic routes, Similarity analyses suggest that the distribution patterns of today’s vent fauna display the strong imprint of the timing and geometry of ancient plate boundaries. Study of past ridge geometry provides a method to predict relationships among vent communities yet to be discovered.