One of the most exciting discoveries made at hydrothermal vents was the presence of an abundant and exotic fauna in the dark, cold part of the ocean, where little life was thought to exist. You can find images of some of these creatures in the image gallery identified above. More important still have been the discoveries of the micro-fauna which exist at hydrothermal vents.
It is now known that certain bacteria can exist in very hot natural waters. These bacteria like the hot-water environment and have been termed 'thermophyllic bacteria'. Much of the research on organisms of this type has been done in hot springs found at the Earth's surface in places such as Yellowstone National Park, USA (http://www.spaceref.com/redirect.html?id=0&url=www.bact.wisc.edu/bact303/b1, http://whyfiles.org/022critters/hot_bact.html) but the results of this work apply equally to studies of deep ocean hydrothermal vents. [For more detail visit the site http://helios.bto.ed.ac.uk/bto/microbes/thermo.htm.]
Studies of the different types of organisms have recently shown that there are three principal domains of life (see http://www.ucmp.berkeley.edu/alllife/threedomains.html), the most primitive of which is the Archaea (http://phylogeny.arizona.edu/tree/life.html and follow the links). Evidence from the RNA evolutionary tree shows that the Archaea are the most primitive of all organisms. All live in extreme environments and some are thermophyllic (http://www.bmb.psu.edu/Courses/micro401/Archaea.JPG). This suggests that life began at high temperatures, or at least very early in its history life passed through a high temperature stage.