One of the things that I find most interesting in social development is the discovery of unexpected linkages between innovations in one field and outcomes in another.
Here is a somewhat hypothetical example. Improvement of long distance banking transactions in Qing China produces an increase in the frequency of rebellion. How so? Because the long distance transport of merchant silver created a sub-culture of rural bandits preying on merchant travelers. The creation of letters of credit reduced these opportunities, and under-employed bandit gangs were more easily recruited into rebel forces. (This corresponds loosely to arguments offered by Liz Perry in Rebels and Revolutionaries in North China, 1845-1945 concerning the dialectic between predation and rebellion, though I've speculated a bit about the banking part.)
The general idea here is that large changes in social systems of interaction -- roads, railways, telegraph systems, etc. -- often create new opportunities for social actors that were not anticipated by designers but that have large social consequences.
Here are some examples of these kinds of effects. Discovery of diamonds in a region leads to severe deforestation (as diamonds stimulate violent conflict, leading to large refugee flows, leading to new destructive uses of forests). Extension of trolleys in the Boston suburbs leads to an increase in the frequency of spikes in disease mortality (as carriers move around the region more frequently). Growth of the electric power grid in Pennsylvania results in a decline in church attendance (as young people find other social options in well-lit towns and cities).
I am led to think about these kinds of effects because of the rapidity of system change in China today. The train system, the extension of video surveillance, changes in social security provisions, the ever-growing population of internal migrants -- all these processes are likely to have unexpected and novel consequences. And as complexity theory tells us, systems with multiple interlinked causal processes are vulnerable to abrupt changes of state as causal factors stimulate unexpected behaviors. This is familiar in ecological research, but it seems equally applicable to the social world.
One consequence of this line of thought is that we need to be cautious about predictions of the future that depend own smooth extrapolations of existing trends. In the case of China, perhaps the most confident prediction we can make is that there will be many surprises in the coming decades.
