: the coming into existence of living things directly from lifeless matter instead of from other living things.
Spontaneous generation, or organic evolution is the 4th stage of evolution (Six Types of Evolution). Nobody knows for sure how it may have happened. All we know is, it doesn't happen today. Things that are living bring forth life while things that are dead, decompose... and then smell.
: the development of life from preexisting life.
Biogenesis is the common occurrence of life bringing forth life, such as dogs having puppies, or the duplication of living cells.
"And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so."-Genesis 1:24