So there are a lot of people who say that the Dark Ages, lasting about 1,000 years, set humans back technologically. However, some say that since the Dark Ages really only affected Western Europe, and not the Middle East or Asia, it wouldn't make a difference.
If there had been no "Dark Ages" there would have been no Renaissance. Historians actually argue about when Renaissance started, and the answer is than it is not possible to pinpoint a date. The Crusade did more to bring the eastern world to western Europe than they did to divide.