( ( Within ( ( the ( last ( tens ( of thousands ) ) ) ) ( of years ) ) ) ( , ( ( ( ( ( ( ( ( woolly mammoths ) , ) ( saber-toothed cats ) ) , ) ( giant sloths ) ) and ) ( other ( marvelous megafauna ) ) ) ( ( ( ( roamed Earth ) , ) ( only ( to ( ( begin ( disappearing ( around ( the ( same time ) ) ) ) ) ( that ( humans ( arrived ( on ( the scene ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Within) (NP (NP (DT the) (JJ last) (QP (NNS tens) (IN of) (NNS thousands))) (PP (IN of) (NP (NNS years))))) (, ,) (NP (NP (JJ woolly) (NNS mammoths)) (, ,) (NP (JJ saber-toothed) (NNS cats)) (, ,) (NP (JJ giant) (NNS sloths)) (CC and) (NP (JJ other) (JJ marvelous) (NN megafauna))) (VP (VBD roamed) (NP (NNP Earth)) (, ,) (S (ADVP (RB only)) (VP (TO to) (VP (VB begin) (S (VP (VBG disappearing) (PP (IN around) (NP (DT the) (JJ same) (NN time))))) (SBAR (IN that) (S (NP (NNS humans)) (VP (VBD arrived) (PP (IN on) (NP (DT the) (NN scene)))))))))) (. .)))
Within the last tens of thousands of years, woolly mammoths, saber-toothed cats, giant sloths and other marvelous megafauna roamed Earth, only to begin disappearing around the same time that humans arrived on the scene.
(ROOT (S (NP (JJ Woolly) (NNS mammoths)) (VP (VBD began) (S (VP (TO to) (VP (VB go) (NP (NP (ADJP (JJ extinct)) (NNS thousands)) (PP (IN of) (NP (NNS years)))) (ADVP (RB ago) (PP (IN because) (PP (IN of) (S (VP (VBG hunting) (PP (IN by) (NP (NNS humans)))))))))))) (. .)))
Woolly mammoths began to go extinct thousands of years ago because of hunting by humans.