Earth-2009 is at a causal bottleneck in the sense that decisions taken now can influence those features of the far future that we consider important, most obviously but not exclusively by causing or preventing the extinction of civilization.
The point I want to make in this post is that, purely as a matter of math, this has to be an extremely unusual state of affairs.
If decisions taken in the 21st century account for 20% of the variance in the value (measured in whatever way) of the universe in 1 million AD, then it cannot be the case that decisions taken in the 22nd through 30th century also each account for 20% of this variance.
A general argument along those lines shows that, for nearly all time periods, if you plot the correlations of the decisions taken in that time period with the values of the universe at times in that period’s future, you’ll get a graph that converges to zero. The past has been an exception. Future people will still be able to influence their future; but the consequences of their actions on the global state of things will be slowly papered over with decisions taken in the future’s future. This will make more emotional sense to humans; common-sense morality assumes people nearby in time are most of what matters.
I’ve made some assumptions here. One of them is that there’s a chance we’ll one day be able to get existential risk down to a negligible level. I believe this to be true, but if not, forget what I said about influencing the long-term future; there will not be one. Another assumption is no boundless growth. With boundless growth, some of the conclusions here are worth re-assessing (does total value increase faster than correlations die out?), but one conclusion that stands is decisions entangled with a fixed fraction of the future’s value — such as those relating to existential risk — are both unique and uniquely important.
As a final worry, if causal bottlenecks are as rare as this argument shows, do we in fact have enough information to overcome the low prior probability that we are in one?