I’m reading Brotherhood of Kings: How International Relations Shaped the Ancient Near East. The book basically outlines the international state system in the ancient Near East which fostered diplomatic relationships between the monarchies of the period. It is noted that this state system and diplomatic culture did not make it through the chaos which marks the transition between what we term the Bronze Age and Iron Age; the centuries between 1200 and 600 BC. I try and read about the ancient Near East when I can, it’s a hard area to find academic books accessible to lay people (I don’t know Sumerian or Akkadian for example, which means that a lot of the philological stuff goes over my head). But thanks the usage of cuneiform tablets which are often well preserved when palaces are burned down we have a substantial amount of records, albeit not of the personable narrative form excluding some exceptions (good for economic historians, not so much for cultural historians).
One thing that seems to jump out to me is that our history can be divided between what came before the transition above, and what came after. If you know about Julian Jaynes you know some argue for a really deep psychological chasm. Setting that aside, consider the cultural continuity of texts between the period after, and the period before. Much of what we know of antiquity in the West is due to translation efforts during the Carolingian period, encyclopediasts in 10th century Byzantium, and the Abbasids in 9th century. These are the major choke points. If it were not for these periods of elite sponsorship of transcription we would be much poorer in antique Greco-Roman works (the maligned Assyrian Empire played that role in the early Iron Age; I believe we have the Epic of Gilgamesh thanks to its libraries).
The cultural chasm between Mycenaean Greece and Classical Greece, a period of 500 years, is arguably greater than that between Classical Greece and 6th century Byzantium. After 1200 BC literate culture disappeared from the Aegean and Anatolia. The societies of the Near East and Egypt were under extreme stress, and their survival was a near thing. Literacy had long disappeared from India (assuming that the Indus Valley script is a full-fledged script, something I suspect it is simply because the society seems too complex and expansive for it not to have more than accounting notation). Western and Indian writing systems derive from the alphabets of the Levant. If the Near East and Egypt had descended into pure barbarism, with Assyria and Egypt being swallowed up in the sea of illiteracy, what would the present look like?
China is the arguable exception to this trend, even though there was a transition from the Shang to the Zhou, I do not know of a major cultural regress during this period in the Far East. Greece remained in a decentralized pre-literate state for centuries. If the West persisted in such a state for far longer what would that mean for us? The Persian Empire, which had control of Central Asia, depended to a large extent on co-opting the political and cultural systems preexistent across its domains. If these regions had remained in a state of barbarism long enough it may be that Chinese culture hegemony in Central Asia would have been robust enough to withstand all the subsequent historical shocks, and world history would look far different.*
* In the period between 0 and 1000 AD Central Asia was contested between China and the Western Eurasian societies. After 1000 AD Central Asia became more fully integrated into Western Eurasian civilization as China withdrew back beyond its geographical perimeter.