Opening DNA sacrifice before life or cambrian period

Not seen the film yet, but have seen interviews and trailers. One trailer caught my eye though. where they show the approach to the opening scene waterfall and the engineer about to sacrifice him DNA i to the waterfall. This is the origins of humans... but was it meant to be the origins of life. The problem is i noticed there was plenty of greenery from plant life - which suggests life already existed. is this meant to be or was it a plothole. If we say its the origin of all life - from a historical scientific point of view, i suppose it would explain the origins of DNA being from an external source which could explain how something so complex arrived on earth. if we say it was the origin of humans, meaning this DNA was implanted during the cambrian period when there was already life but new DNA added here caused the cambrian explosion as its known in biology and ultimately resulted in human evolution. thetrailer suggests this scene is during the cambrian period which is why there is greenery already. i prefer a story which says DNA itself originated withthe engineers