( ( These organisms ) ( ( ( lived ( long ( ( ( before ( ( the ( first build-up ) ) ( of ( oxygen ( in ( the atmosphere ) ) ) ) ) ) , ) perhaps ) ) ) ( as ( early ( ( as ( ( 3.5 billion ) years ) ) ago ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS organisms)) (VP (VBD lived) (ADVP (RB long) (PP (IN before) (NP (NP (DT the) (JJ first) (NN build-up)) (PP (IN of) (NP (NP (NN oxygen)) (PP (IN in) (NP (DT the) (NN atmosphere)))))) (, ,) (ADVP (RB perhaps)))) (ADVP (RB as) (RB early) (PP (IN as) (NP (QP (CD 3.5) (CD billion)) (NNS years))) (RB ago))) (. .)))
These organisms lived long before the first build-up of oxygen in the atmosphere, perhaps as early as 3.5 billion years ago.
(ROOT (S (NP (DT The) (JJ first) (VBG living) (NNS cells)) (VP (MD may) (VP (VB have) (VP (VBN evolved) (ADVP (NP (QP (RB around) (CD 4) (CD billion)) (NNS years)) (RB ago))))) (. .)))