( ( the answer ) ( ( ( ( is elusive ) , ) ( because ( humans ( have ( a ( unique ( ability ( to ( ( ( manipulate ( their environment ) ) and ) ( ( expand ( its ( supporting capacity ) ) ) ( through ( ( technology and ) trade ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT the) (NN answer)) (VP (VBZ is) (ADJP (JJ elusive)) (, ,) (SBAR (IN because) (S (NP (NNS humans)) (VP (VBP have) (NP (DT a) (JJ unique) (NN ability) (S (VP (TO to) (VP (VP (VB manipulate) (NP (PRP$ their) (NN environment))) (CC and) (VP (VB expand) (NP (PRP$ its) (JJ supporting) (NN capacity)) (PP (IN through) (NP (NN technology) (CC and) (NN trade)))))))))))) (. .)))
the answer is elusive, because humans have a unique ability to manipulate their environment and expand its supporting capacity through technology and trade.
(ROOT (S (NP (NNS Humans)) (VP (VBP are) (ADJP (JJ unique) (PP (IN in) (NP (PRP$ their) (NN ability) (S (VP (TO to) (VP (VB alter) (NP (PRP$ their) (NN environment)) (PP (IN with) (NP (NP (DT the) (JJ conscious) (NN purpose)) (PP (IN of) (NP (NP (JJ increasing) (VBG carrying) (NN capacity)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ acts) (PP (IN as) (NP (NP (DT a) (JJ limiting) (NN factor)) (PP (IN on) (NP (NP (NNS populations)) (PP (IN in) (NP (NN general))))))))))))))))))))) (. .)))