It was noted that the Mesopotamian/Sumerian city of Eridu
(founded around 5000-BC) had reached the unusually large
size of about 25 acres and a pop of maybe 4000 by 2900-BC.
I wonder how many good bars/nightclubs ? :-)

"In some, but not all, versions of the Sumerian King List,
Eridu is the first of five cities where kingship was received
before a flood came over the land"

.. . .

Note that the "flood(s)" were surely the result of the
last ice-age ending. The melting ice would have created
VAST quantities of water to the north, just looking for
a path to the (rising) sea. In Sumeria both the Tigris
and Euphrates rivers would have carried the floodwaters
south into Sumeria FAST. Would have seemed like the end
of the world to many at the time.

Oh yea ... 4004-BC ? Sorry, but there were lots of
smart civs going by then. There were a bunch of
city-states in Sumeria into literature and architecture,
irrigation, math and astronomy.

The earliest "civs" there - beyond the village/tribe
scale and sophistication, likely date back to around
11,000-BC. The megalithic site of Gobekli Tepe in
current southern Turkey dates to around that time.
It could only have been created by cooperative
labor, some common-ish religion and a PLAN.

Remains of odd circular mud-brick homes forming tiny
cities have been found near there dating to around
10,000-BC ... you entered through a door in the ROOF
and when family members died you buried them in the
FLOOR. Yes Billy, grandma IS still with us ... :-)

I *suspect* that there were even earlier civs that
formed DURING the ice-age. Alas most would have
been near the sea for good reasons, even better where
a river met the sea. Sea-level was 300 feet lower
than than today. If you're gonna find them you'll
need a submarine or big-ass dredge and a lot
of luck.

India/China ... so far there's no evidence they
developed civs that far back. Of course the heavy
land-use since and wetter clime MAY have obliterated
a lot of ancient sites. Deserts preserve, jungles
consume.