( ( The ( first ( eukaryotic cells ) ) ) ( ( appeared ( ( ( about ( 1.5 billion ) ) years ) ago ) ) . ) )
(ROOT (S (NP (DT The) (JJ first) (JJ eukaryotic) (NNS cells)) (VP (VBD appeared) (ADVP (NP (QP (RB about) (CD 1.5) (CD billion)) (NNS years)) (RB ago))) (. .)))
The first eukaryotic cells appeared about 1.5 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))))) (. .)))