The 4th millennium BC spanned the years 4000 BC to 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.
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.[1]
^Jean-Noël Biraben (1979). "Essai sur l'évolution du nombre des hommes". Population. 34 (1): 13–25. doi:10.2307/1531855. JSTOR1531855. S2CID143406315., estimates 40 million at 5000 BC and 100 million at 1600 BC, for an average growth rate of 0.027% p.a. over the Chalcolithic to Middle Bronze Age.