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For Darwin's theory of evolution by natural
selection to be viable, the Earth had to be very old. In Darwin's lifetime, people
estimated the Earth's age by the thickness of sedimentary layers. These early estimates
concluded that the sedimentary rocks in Great Britain, for example, were about 12 million
years old -- old enough for evolution to have taken place. It wasn't until the twentieth
century that more reliable methods of estimating the age of the Earth -- radioactive
dating -- were developed. For information on relative
and radiometric
dating of fossils, watch the Evolution Library video segment "Radiometric
Dating." |
