Answer: The period that started 4000 b.c. is important because it is the period when the earliest civilizations flourished and inventions were made. Earliest known civilization arises in Sumer (4500–4000 B.C
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.
