( ( Many scientists ) ( ( believe ( that ( ( simple life ) ( ( ( arose ( on Earth ) ) ( ( ( more ( ( than four ) billion ) ) years ) ago ) ) ( after ( meteorites ( ( ( crashed ( through ( the atmosphere ) ) ) , ) ( ( carrying ( amino ( acids ( and ( other ( biochemical compounds ) ) ) ) ) ) ( from ( outer space ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Many) (NNS scientists)) (VP (VBP believe) (SBAR (IN that) (S (NP (JJ simple) (NN life)) (VP (VBD arose) (PP (IN on) (NP (NNP Earth))) (ADVP (NP (QP (JJR more) (IN than) (CD four) (CD billion)) (NNS years)) (RB ago)) (SBAR (IN after) (S (NP (NNS meteorites)) (VP (VBD crashed) (PP (IN through) (NP (DT the) (NN atmosphere))) (, ,) (S (VP (VBG carrying) (NP (JJ amino) (NNS acids) (CC and) (JJ other) (NN biochemical) (NNS compounds)) (PP (IN from) (NP (JJ outer) (NN space)))))))))))) (. .)))
Many scientists believe that simple life arose on Earth more than four billion years ago after meteorites crashed through the atmosphere, carrying amino acids and other biochemical compounds from outer space.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD four) (NNS classes)) (PP (IN of) (NP (JJ biochemical) (NNS compounds))))) (. .)))