Complex sentence: The anthropologist fills in with comparisons to other cultures and is forced to rely on theories that have no evidential basis whatsoever, the old notion of universal stages of development or the claim that cultural resemblances are based on some unrecognized past contact between groups.
Split into simpler sentences: The anthropologist fills in with comparisons to other cultures and is forced to rely on theories that have no evidential basis. The old notion of universal stages of development or the claim that cultural resemblances are based on some unrecognized past contact between groups.