( ( Even ( though ( ( no ( archaeological evidence ) ) ( has ( confirmed it ) ) ) ) ) ( , ( ( the ( spiral ( ramp theory ) ) ) ( ( has ( been ( widely ( accepted ( among ( scientific circles ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (RB Even) (IN though) (S (NP (DT no) (JJ archaeological) (NN evidence)) (VP (VBZ has) (VP (VBN confirmed) (NP (PRP it)))))) (, ,) (NP (DT the) (NN spiral) (NN ramp) (NN theory)) (VP (VBZ has) (VP (VBN been) (VP (ADVP (RB widely)) (VBN accepted) (PP (IN among) (NP (JJ scientific) (NNS circles)))))) (. .)))
Even though no archaeological evidence has confirmed it, the spiral ramp theory has been widely accepted among scientific circles.
(ROOT (S (NP (NN Evidence)) (VP (VBZ allows) (S (NP (NNS theories)) (VP (TO to) (VP (VB be) (VP (ADVP (RB widely)) (VBN accepted)))))) (. .)))