This stability ended with the climate event known as the 4.2 kiloyear event — a prolonged drought that struck the Middle East and North Africa around 2200 BCE, approximately coinciding with the end of the Old Kingdom and the beginning of the First Intermediate Period.

This drought, which is now well-documented in the paleoclimatic record, caused severe agricultural disruption across a wide area, including in Egypt.

Insufficient Nile floods meant crop failures.

Crop failures meant famine.

Famine meant political instability.

The First Intermediate Period that followed the Old Kingdom collapse was a time of political fragmentation, regional conflict, and reduced central authority.

The great pyramid-building projects ceased.

The elaborate royal burials became less standardized and less spectacular.