Discoveries
1907	Radiometric dating finds Earth is 2.2 billion years old
1912	Wegener proposes idea of continental drift
1947	Libby introduces radiocarbon dating
1953	Piltdown Man is revealed as fake
1953	Watson and Crick describe structure of DNA
1953	Amino acids are created in laboratory
1953	Great Global Rift is discovered
1959	Leakey family discovers human ancestors
1960	Hess proposes sea-floor spreading
1963	Magnetic bands provide evidence of sea-floor spreading
1974	Johanson finds 3.2 million-year-old Lucy
1977	Life is found near deep ocean vents
1980	Alvarez finds evidence of dinosaur-killing asteroid
1994	4.4 million-year-old human ancestor is found
1996	Meteorite from Mars points to possibility of life on other planets