Some of the first geologists came from ancient Greece and Egypt. Later, scientists in China studied how land was formed and figured out how erosion wears away mountains, rocks, and other landforms. Scottish scientist James Hutton's The Theory of the Earth became the basis for modern geology. William Smith started out as a farmer, but went on to create what is thought to be the first geologic map. German Friedrick Mohs studied minerals and came up with a hardness identification scale that is still used by every geologist.