4th millennium BC


The 4th millennium BC spanned the years 4000 through 3001 BC. Some of the major changes in human culture during this time included the beginning of the Bronze Age and the invention of writing, which played a major role in starting recorded history.
is an archaeological site in northern Sardinia, Italy, located in the territory of Sassari near Porto Torres. 4th millennium BC.
The city states of Sumer and the kingdom of Egypt were established and grew to prominence. Agriculture spread widely across Eurasia.
World population growth relaxes after the burst due to the Neolithic Revolution. World population is largely stable, at roughly 50 million, with a slow overall growth rate at roughly 0.03% p.a.

Culture

;Near East
;Europe
;Central Asia
;East Asia
;South Asia
;Americas
;Australia
;Sub-Saharan Africa
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.
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.

Environment

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 as hypothesized by Ohio State University.