( ( Although ( ( some scientists ) ( have ( theorized ( that ( ( multicellular ( life forms ) ) ( evolved ( ( ( as ( much ( ( as a ) billion ) ) ) years ) ago ) ) ) ) ) ) ) ) ( , ( ( the ( first ( multicellular ( life forms ) ) ) ) ( ( found ( in ( ( the ( fossil record ) ) ( lived ( ( ( about ( 600 million ) ) years ) ago ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Although) (S (NP (DT some) (NNS scientists)) (VP (VBP have) (VP (VBD theorized) (SBAR (IN that) (S (NP (NN multicellular) (NN life) (NNS forms)) (VP (VBD evolved) (ADVP (NP (QP (RB as) (JJ much) (IN as) (DT a) (CD billion)) (NNS years)) (RB ago))))))))) (, ,) (NP (DT the) (JJ first) (NN multicellular) (NN life) (NNS forms)) (VP (VBD found) (PP (IN in) (NP (NP (DT the) (JJ fossil) (NN record)) (VP (VBN lived) (ADVP (NP (QP (RB about) (CD 600) (CD million)) (NNS years)) (RB ago)))))) (. .)))
Although some scientists have theorized that multicellular life forms evolved as much as a billion years ago, the first multicellular life forms found in the fossil record lived about 600 million 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))))) (. .)))