(S (S (BASENP (NNS Researchers)) (VP (VBP say) (SBAR (IN that) (S (NP (NP (ADJP (ADJP (JJ new)) (COMMA ,) (ADJP (NN ten) (JJ million-year-old))) (NNS fossils)) (VP (VBN found) (PP (IN in) (BASENP (NNP Ethiopia))))) (COMMA ,) (VP (VBP prove) (SBAR (SBAR (IN that) (S (NP (NP (BASENP (DT the) (NN theory)) (SBAR (IN that) (S (BASENP (NNS humans)) (VP (MD may) (VP (VB have) (VP (VP (VBN evolved) (PP (IN from) (NP (BASENP (DT a) (NN species)) (PP (IN of) (BASENP (JJ great) (NNS apes)))))) (ADVP (BASENP (QP (NN eight) (NN million)) (NNS years)) (RB ago)))))))) (COMMA ,)) (VP (VP (MD may) (RB not)) (VP (VB be) (ADJP (JJ true)))))) (CONJP (COMMA ,) (CC but)) (SBAR (IN that) (S (BASENP (NNS humans)) (VP (MD may) (VP (VB have) (VP (VP (VBN split) (PP (IN from) (BASENP (NNS apes)))) (ADVP (NP (QP (ADJP (ADJP (RB as) (JJ long)) (IN as)) (BASENP (NN 10.5) (NN million))) (NNS years)) (RB ago))))))))))))) (PERIOD .))