(S (S (ADVP (RB However)) (COLON ;) (S (NP (BASENP (NNP Dr.) (NNP Bogaert) (POS 's)) (NN study)) (VP (VBD made) (NP (BASENP (DT no) (NN explanation)) (PP (IN for) (NP (BASENP (DT the) (NN origin)) (PP (IN of) (BASENP (NN lesbianism))))))))) (PERIOD .))