c. 10,950 BCE · climate record
A world disrupted
The Younger Dryas began about 12,900 years before 1950: an abrupt return to colder conditions across much of the Northern Hemisphere. Its approximate onset is close to this model's 10,948 BCE quarter turn. Its effects varied by region, so the comparison concerns an approximate climatic boundary.
NOAA · Younger Dryas chronology ↗
5500–3200 BCE · southern Mesopotamia
The Sumerian transformation
Sumer belongs among humanity's earliest urban civilizations. Ubaid communities (c. 5500–4000 BCE) built irrigation systems and growing settlements; by c. 3200 BCE, Uruk was a major city using pictographic accounts. Urban life and writing emerged through a long development from earlier communities.
The chart's Silver Gate at 4468 BCE falls within the Ubaid period, more than a millennium before that writing milestone. The interval separates the earlier settlement landscape from the later writing milestone.
20th–21st centuries · a connected world
The modern acceleration
Within a century, electronics, global communication, genomics and artificial intelligence have changed what people can build and understand. The Web began at CERN in 1989; by 2025, ITU estimated that six billion people were online. Discoveries increasingly become tools for further discovery.
Progress is uneven: “exponential” describes particular measurements over particular intervals. These milestones span decades on either side of the model's 2012 anchor, giving the present a broad historical context.
ITU · connectivity in 2025 ↗