In evolutionary biology, a group of organisms have common descent if they have a common ancestor. There is strong support for the theory that all living organisms on Earth are descended from a common ancestor.[1][2]
Charles Darwin proposed the theory of universal common descent through an evolutionary process in On the Origin of Species, saying, "There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one".[3]p490
The last universal ancestor (LUA) (or last universal common ancestor, LUCA), is the most recent common ancestor of all currently living organisms.[1] It is believed to have appeared about 3.9 billion years ago.[4][5]
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↑Darwin, Charles; Costa, James T. 2009. The Annotated Origin: a facsimile of the first edition of On the Origin of Species, annotated by James T. Costa. Cambridge, Massachusetts: Belknap Press of Harvard University. ISBN978-0-674-03281-1