Text: When Celtic peoples crossed the Pyrenees in the first millennium b.c., they intermarried with the existing Iberian population and built a series of hilltop fort communities or citanias, the finest example of which is at Briteiros (see page 73).
Entailment: Some Celtic people intermarried with Iberians and built their own communities.
Contradiction: When the Iberian people crossed the Pyrenees, they exterminated the Celtic people.