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spec: We did n't have the fangs , claws , or speed necessary to make good predators ; we did n't have the robust and complicated digestive systems necessary for successful browsing or grazing , so we could n't live on grasses and shrubs . '' The mix of mystical solemnity and chain-reaction slapstick suggests a Road Runner cartoon directed by John Woo , `` wrote Matt Zoller Seitz in the New York Times . Thus , it is important to have a robust and comprehensive causal model that explains how these consequences arise so as to help all parties involved to prevent these consequences . Carl Sagan put it bluntly : " If it were widely understood that claims to knowledge require adequate evidence before they can be accepted , there would be no room for pseudoscience .