(i got this from) www.myweb.usf.edu/~ppamphil/page2.html Darwin found that his observations were consistent with the theory of geologists charles lyell which started that the earths surface is undergoing consistent change from his observations, darwin also relized that certain fossils of extinct species closely resembled living species in the same geographical area. while on the galapagos islands, darwin observed that each island supported its own form of tortoise, mockingbird, and finch. the various forms of each island were closely related but differed i. structure and eating habbits. these observations led to darwins most important contribution to the feild of biology, the theory of natural selection.