What is the earliest possible change to history anyone can think of, that has significantly disruptive effects on actual history?
Doesn't include physical, geological, or biological changes. Must be something along the lines of someone doing something differently, or a small change in human affairs. Cannot be too sweeping, e.g, 'No agricultural revolution'.
The earliest change I can think of would be something around the unification of Egypt, c3100 BCE . Perhaps Naqada conquers Thinis instead of vice-versa, leading to an Egypt with a subtly different character, or a failed unification.
Any thoughts?