When one studies the great eras, periods, trends and technological innovations of Western civilization, it's difficult to credibly single out the actions of a single individual to construct a believable counter-factual that would alter or eliminate an entire era. When one takes a satellite view of history, it's almost impossible to believe history is shaped almost entirely by individuals -- great men or great women.
If you outline European history, for example, it's difficult if not impossible to argue that any of these eras would not exist if individuals had acted differently:
- Ancient (Paleolithic, Mesolithic, Neolithic eras; Bronze Age, Iron Age);
- Classical (Greece and Rome),
- Medieval (Post-Roman Antiquity;
- Carolingian Era [Charlemagne];
- Post-Carolingian Era [Viking and other European invasions — Anglo-Saxons; Normans;
- High Middle Ages;
- Late Middle Ages;
- Modern Era (beginning with Renaissance; continuing with Reformation; Baroque Era; Age of Empires; Colonialism; Revolutions; Industrial Age)
- 20th Century — collapse of empires, world wars, discredit of colonialism and nationalism to the formation of the European Union.