The premise
Darwinian natural selection.
Simple as that.
"Nothing in Biology Makes Sense Except in the Light of Evolution" – title of a 1973 essay by the evolutionary biologist Theodosius Dobzhansky. [1]
Go now to the assumptions and observations.
Notes
1. See a discussion late 2008 by Richard Nikoley and Robb Wolf about the Darwinian/evolutionary paradigm.
Page updated 5 May 2010