( ( The ( exponent ( less ( than 1 ) ) ) ) ( ( indicates ( that ( ( small mammals ) ( ( ( have ( ( ( relatively large ) brains ) ( compared ( to ( body size ) ) ) ) ) , ) ( probably ( because ( they ( have ( ( relatively large ) heads ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ exponent) (QP (JJR less) (IN than) (CD 1))) (VP (VBZ indicates) (SBAR (IN that) (S (NP (JJ small) (NNS mammals)) (VP (VBP have) (NP (NP (ADJP (RB relatively) (JJ large)) (NNS brains)) (PP (VBN compared) (PP (TO to) (NP (NN body) (NN size))))) (, ,) (SBAR (ADVP (RB probably)) (IN because) (S (NP (PRP they)) (VP (VBP have) (NP (ADJP (RB relatively) (JJ large)) (NNS heads))))))))) (. .)))
The exponent less than 1 indicates that small mammals have relatively large brains compared to body size, probably because they have relatively large heads.
(ROOT (S (NP (JJ Placental) (NNS mammals)) (VP (VBP give) (NP (NN birth)) (PP (TO to) (NP (ADJP (RB relatively) (JJ large)) (NNS fetuses)))) (. .)))