I'm head-down, redrafting a book right now. But in the meantime, I am mulling over a question.

Assume you are a historian in the 30th century, compiling a pop history text about the period 1700-2300AD. What are the five most influential factors in that period of history?

Please note that this is a 600 year span—around the duration of the entire mediaeval period. Events a mere 20 years apart, such as the first and second world wars, merge together when viewed through the wrong end of a temporal telescope, just like the 30 years' war or the Wars of the Roses. Individual people, even hugely influential thinkers and rulers and tyrants, are a jumbled mass of names with dates attached. This is a question about the big issues—the ones big enough to remember half a millennium hence, like the Black Death, the Crusades, or the conquest of the Americas.

I'm not asking for specific historical events but for major trends. Anthropogenic climate change is obviously one of the big ones, and I have a number of others in mind; I want to see if I've missed anything obvious.

(For the sake of argument we assume: no singularity/rapture of the nerds, no breakthroughs that lead to wholesale invalidation of the known laws of physics, and no catastrophic events that render humanity extinct, destroy all archival records, or consign us all to a pre-industrial level of civilization.)