Cypress:
Darwin's theory relies on the existence of a common biologic ancestor. He even proposed abiogenesis theory (life coming to life from non-life by itself) in a letter to his friend, Joseph Hooker.
In a February 1, 1871, letter to his friend Joseph Dalton Hooker suggested that the original spark of life may have begun in a:
"...warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity, etc. present, so that a protein compound was chemically formed ready to undergo still more complex changes."
Darwin went on to explain in that same letter that:
"...at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed."
Below is the full quotation followed by the weblink:
"It is often said that all the conditions for the first production of a living organism are present, which could ever have been present. But if (and Oh! what a big if!) we could conceive in some
warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc., present, that a protein compound was chemically formed ready to undergo still more complex changes, at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed."
http://www.daviddarling.info/encyclopedia/D/DarwinC.html