
The 4th millennium BC spanned the years 4000 BC to 3001 BC. It marked a critical turning point in human history, characterized by the transition from late Neolithic agricultural societies into urban, state-level civilizations.
This millennium witnessed the invention of writing, the initial spread of bronze metallurgy, the adoption of the wheeled vehicle, and the rise of the first primary states in Mesopotamia and Ancient Egypt, effectively initiating recorded history.
The city states of Sumer and the (Predynastic) Kingdom of Egypt were established and grew to prominence. Agriculture spread widely across Eurasia.
World population growth relaxed after the burst that came about from the Neolithic Revolution. World population was largely stable in this time at roughly 50 million, growing at an average of 0.027% per year.
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| Neolithic cultures |
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| ↑ Mesolithic |
| ↓ Chalcolithic |






Metallurgy during the Copper Age developed in Europe.




The Americas were in the Meso-Indian (Archaic) stage.
Sub-Saharan Africa remains in the Paleolithic period, except for the earliest neolithization of the Sahel following the desiccation of the Sahara in c. 3500 BC. As the grasslands of the Sahara began drying after 3900 BC, herders spread into the Nile Valley and into eastern Africa (Eburan 5, Elmenteitan). The desiccation of the Sahara and the associated neolithisation of West Africa is also cited as a possible cause for the dispersal of the Niger-Congo linguistic phylum.
| Preceded by the Pleistocene |
| Holocene Epoch |
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Blytt–Sernander stages/ages
*Relative to year 2000 (b2k). †Relative to year 1950 (BP/Before "Present"). |
Based on studies by glaciologist Lonnie Thompson, professor at Ohio State University and researcher with the Byrd Polar Research Center, a number of indicators shows there was a global change in climate 5,200 years ago, probably due to a drop in solar energy output.
* HINDUISM: Myths of time and eternity: The fourth and most degenerate yuga (Kali) began in 3102 BCE and will last 432,000 years. At the close of the Kali yuga, the world will be destroyed by fire and flood, to be re-created as the cycle resumes.
The current Kali Yuga (Iron Age) began at midnight on 17/18 February 3102 BC in the proleptic Julian calendar.