|the seas and atmosphere on earth before the existence of life, primarily containing a mixture of water, hydrogen, methane, ammonia, and carbon dioxide|
|any modern theory of evolution holding that species evolve by natural selection acting on genetic variation|
endogenous en·dog·e·nous (ěn-dŏj'ə-nəs)
Originating or produced within an organism, a tissue, or a cell.
Caused by factors within the body. Used of a disease.