( It ( ( follows ( that ( ( these ( two sub-orders ) ) ( have ( evolved ( from ( the ( common ancestors ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ follows) (SBAR (IN that) (S (NP (DT these) (CD two) (NNS sub-orders)) (VP (VBP have) (VP (VBN evolved) (PP (IN from) (NP (DT the) (JJ common) (NNS ancestors)))))))) (. .)))
It follows that these two sub-orders have evolved from the common ancestors.
(ROOT (S (NP (NP (DT The) (NN conclusion)) (SBAR (IN that) (S (NP (CD two) (NN animal) (NNS species)) (VP (VBD evolved) (PP (IN from) (NP (DT a) (JJ common) (NN ancestor))) (PP (IN in) (NP (JJ recent) (JJ geological) (NN history))))))) (VP (VBZ is) (ADVP (RBS best)) (VP (VBN supported) (PP (IN by) (NP (DT the) (NN observation))) (SBAR (IN that) (S (NP (DT the) (NNS species)) (VP (VBP have) (NP (JJ similar) (NN bone) (NN structure))))))) (. .)))
The conclusion that two animal species evolved from a common ancestor in recent geological history is best supported by the observation that the species have similar bone structure.