Hi, Nina. Sorry for the delay in responding; I was on the road (and in the air). The main reason is because we want to put an emphasis on the Bible history alongside the world history. We didn’t want to squeeze Genesis through Acts into one year, so we spread it out and put the Ancients with those Bible readings. It turned out that three years was a much nicer pace and allowed the students to linger in the Bible accounts in their historical settings.