Is humanity doomed? We certainly don’t lack apocalyptic scenarios: nuclear war, a robot uprising, out-of-control climate change. Unlikely, far-fetched? Not according to scientists and mathematicians who, in recent decades, have found a surprising new source for anxiety about the long-term survival of the human race: probability theory. The so-called “doomsday argument” holds that there is a 50% chance that the end of human life will come within 760 years.
That is the opening paragraph from a
n essay by William Poundstone in the
Wall Street Journal. He also was a recent guest on
Michael Shermer's Science Salon podcast discussing the wide implications for this elegant theory.
Also from the essay:
Since it is equally likely that those of us living today are in the first or second half of all past and future human births, let’s say that we are in the second half—which would mean that there are no more than 100 billion births yet to come. There is a 50% chance that is true, which at the current global birthrate (about 131 million a year) translates to a 50% chance that we have at most 760 more years of births. A changing birthrate would modify that estimate, but the calculation is that simple.
A friend forwarded the original link to me and we had a bit of discussion on it basically agreeing that the math and process is compelling, but that it seems to be missing something to make it as much as it seems to be. Specifically, I find it very interesting, but it seems to me like a confusion between or muddling of two different concepts.
One (German tanks) is like a kid turning to a football game on TV randomly and guessing about how much longer in real time (not game time) the game will last. The other (humanity) is like being a kid on vacation who wakes up in a car wanting to know "are we
halfway there yet." The second case is much harder to answer if we include a key condition that the destination distance is not known by the kid. Even if he knows he is 100 miles from his house in OKC, he doesn’t know if the destination is
Branson or
New York City or elsewhere. It is much easier to ascertain where he might be in the football game as opposed to the vacation. A score of 14-7 and a flash of the scoreboard showing "3rd Quarter" is much more revealing than a road sign that has a highway number inside a Missouri silhouette. While he can apply the analysis in both cases, his prediction revisions will be orders of magnitude different as time passes for the vacation as compared to the football game.
Another problem I have is that the time frame is inversely proportionate to the future population growth rate. If we slow birthrates down to just above replenishment (about 2.1 births/woman), then we extend the time between now and the next 100 billion people. Thomas Malthus and Paul Ehrlich might agree, but Jean-Baptiste Say and Julian Simon (and I myself) would not. So my complaint boils down to: that when applied to something like humanity and it’s future, this doomsday calculation is not telling us as much as it is purporting to.
