Proto-writing:

Chinese proto-writing

European proto-writing

Indus Valley seals

Indus valley seal impression, possibly script

The spread of agriculture

1. Mesopotamia (Sumer):
Sumer (/ˈsuːmər/)^{[note 1]} was the first ancient urban civilization in the historical region of southern Mesopotamia, modern-day southern Iraq, during the Chalcolithic and Early Bronze ages, and arguably the first civilization in the world.^[1]

Proto-writing in the region dates back to c. 3500 BC. The earliest texts come from the cities of Uruk and Jemdet Nasr and date back to 3300 BC; early cuneiform writing emerged in 3000 BC.^[2]

Cities of Sumer

Modern historians have suggested that Sumer was first permanently settled between c. 5500 and 4000 BC by a West Asian people who spoke the Sumerian language (pointing to the names of cities, rivers, basic occupations, etc., as evidence), a language isolate.^{[3][4][5][6] …}

Sumerian culture seems to have appeared as a fully formed civilization, with no pre-history. …

Uruk, one of Sumer’s largest cities, has been estimated to have had a population of 50,000-80,000 at its height;^[28] given the other cities in Sumer, and the large agricultural population, a rough estimate for Sumer’s population might be 0.8 million to 1.5 million. The world population at this time has been estimated at about 27 million.^[29]…

Babylonian math homework*

The Sumerians developed a complex system of metrology c. 4000 BC. This advanced metrology resulted in the creation of arithmetic, geometry, and algebra. From c. 2600 BC onwards, the Sumerians wrote multiplication tables on clay tablets and dealt with geometrical exercises and division problems. The earliest traces of the Babylonian numerals also date back to this period.^[45] The period c. 2700 – 2300 BC saw the first appearance of the abacus, and a table of successive columns which delimited the successive orders of magnitude of their sexagesimal number system.^[46] The Sumerians were the first to use a place value numeral system. … They were the first to find the area of a triangle and the volume of a cube.^{[47] …}

* “Babylonian clay tablet YBC 7289 with annotations. The diagonal displays an approximation of the square root of 2 in four sexagesimal figures, 1 24 51 10, which is good to about six decimal digits.
1 + 24/60 + 51/60² + 10/60³ = 1.41421296… The tablet also gives an example where one side of the square is 30, and the resulting diagonal is 42 25 35 or 42.4263888…”

Continuing on:

Sumerian tablet recording the allocation of beer

Commercial credit and agricultural consumer loans were the main types of loans. The trade credit was usually extended by temples in order to finance trade expeditions and was nominated in silver. The interest rate was set at 1/60 a month (one shekel per mina) some time before 2000 BC and it remained at that level for about two thousand years.^[49] Rural loans commonly arose as a result of unpaid obligations due to an institution (such as a temple), in this case the arrears were considered to be lent to the debtor.^[50] They were denominated in barley or other crops and the interest rate was typically much higher than for commercial loans and could amount to 1/3 to 1/2 of the loan principal.^[49]

Periodically “clean slate” decrees were signed by rulers which cancelled all the rural (but not commercial) debt and allowed bondservants to return to their homes. … The first known ones were made by Enmetena and Urukagina of Lagash in 2400-2350 BC. According to Hudson, the purpose of these decrees was to prevent debts mounting to a degree that they threatened fighting force which could happen if peasants lost the subsistence land or became bondservants due to the inability to repay the debt.^{[49] …}

Examples of Sumerian technology include: the wheel, cuneiform script, arithmetic and geometry, irrigation systems, Sumerian boats, lunisolar calendar, bronze, leather, saws, chisels, hammers, braces, bits, nails, pins, rings, hoes, axes, knives, lancepoints, arrowheads, swords, glue, daggers, waterskins, bags, harnesses, armor, quivers, war chariots, scabbards, boots, sandals, harpoons and beer. The Sumerians had three main types of boats:

• clinker-built sailboats stitched together with hair, featuring bitumen waterproofing
• skin boats constructed from animal skins and reeds
• wooden-oared ships, sometimes pulled upstream by people and animals walking along the nearby banks

… The Sumerians’ cuneiform script is the oldest (or second oldest after the Egyptian hieroglyphs) which has been deciphered (the status of even older inscriptions such as the Jiahu symbols and Tartaria tablets is controversial).

Reconstructed Neo-Sumerian Great Ziggurat of Ur, near Nasiriyah, Iraq

Lamassu Designs has made a lovely infographic on the Sumerian/Mesopotamian calendar/numerical system, which for some reason is failing to download properly. So I’m screencapping it for you:

marsh near the mouths of the Tigris and Euphrates rivers

Reconstructed Sumerian finery