( ( Recent studies ) ( ( have ( ( bolstered ( the hypothesis ) ) ( that ( ( human hunting ) ( ( contributed ( to ( ( the extinction ) ( of ( Pleistocene animals ) ) ) ) ) ( ( ranging ( from ( ( the ( woolly mammoth ) ) ( to ( the ( giant wombat ) ) ) ) ) ) ( to ( the ( North ( American camel ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Recent) (NNS studies)) (VP (VBP have) (VP (VBN bolstered) (NP (DT the) (NNS hypothesis)) (SBAR (IN that) (S (NP (JJ human) (NN hunting)) (VP (VBD contributed) (PP (TO to) (NP (NP (DT the) (NN extinction)) (PP (IN of) (NP (NNP Pleistocene) (NNS animals))))) (S (VP (VBG ranging) (PP (IN from) (NP (NP (DT the) (JJ woolly) (NN mammoth)) (PP (TO to) (NP (DT the) (JJ giant) (NN wombat))))) (PP (TO to) (NP (DT the) (NNP North) (NNP American) (NN camel)))))))))) (. .)))
Recent studies have bolstered the hypothesis that human hunting contributed to the extinction of Pleistocene animals ranging from the woolly mammoth to the giant wombat to the North American camel.
(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.