Although the evidence was subsequently contested, some single - celled microbial life lacking a nucleus that segregates their internal DNA or RNA («prokaryotes») from the surrounding cytoplasm may have flourished in darkness within cracks in Earth's seafloor crust and around deep, warm or
boiling hot ocean springs (hydrothermal or
volcanic vents, such as at Lost City or at black smokers) without a need for light or free oxygen in the oceans or atmosphere.