Zooming in again, this time on the last 14-15,000 years before the present, we see, barely, to the left, the climate rising rapidly from Glacial Maximum conditions up to temperatures similar to what we have today, and then crashing down to GM conditions again (with a few hiccups on the way). Then, after a thousand freezing years, it rises again like a shot. But this time it levels out quite quickly onto a fairly stable, warm plateau: the Holocene Interglacial. We see, moreover, that since about 5,000 BP, average temperatures have slowly declined, reaching a temporary low with the Little Ice Age that started in the 1300's and lasted till the mid-19th century, when temperatures picked up again, due, most likely, to humanly induced global warming. Lacking this influence, we might well imagine the climate slowly continuing to grind down into a new glaciation (about time, too, interglacials typically last about 10,000 years, and ours has by now lasted nearly 12,000). How the temporary human-induced global warming will affect this picture is anyone's guess.
 
Returning to the timeline, note how cattle and horses are tamed and introduced to the Eurasian steppes, just in time for the great Indo-European expansion that starts about 6,000 years ago on the plains North of the Black Sea, and slowly spreads to Europe, India and parts of the Middle East.
 
Note also how farming spreads from the Levant to North Africa, the Middle East, South Asia, and ultimately Europe. There is no evidence for the spread of farming from the Middle East to China, which undoubtedly originated agriculture autonomously, as did other regions, notably the Americas.
 
Agriculture has vast needs for coordinated irrigation, terracing and land-improvement work, it makes imperative demands that peasants live on the land in order to control it, it affirms the need for authorities to mediate the inevitable conflicts that arise in the tight-knit communities. All of these needs are best safeguarded by a central pillar: a God, a King, an Emperor. By this logic, again and again, across the Earth, empires have arrived, in short spurts and constant changes (Mesopotamia), in long, stable dynastic reigns with few interruptions (Egypt), in the parallel lineages of multiple empires (India), or in all-encompassing "global" dynasties (China).
 
Further to the right on the timeline we discern the Roman Empire, and beyond that the Black Death, and beyond that, barely, the Industrial Revolution. Even at this magnification our concerns seem very small.