Complex sentence: Although there has been an undertone of development within the association with human rights earlier than this time; it has been since the end of the 20th century when there were known links of combining development and human rights into the same efforts.
Split into simpler sentences: Although there has been an undertone of development with the association with human rights earlier than this time. It has been since the end of the 20th century when there were known links of combining development and human rights into the same efforts.