By Taylor Marvin
I recently attended the Arthur C. Clarke Center for Human Imagination’s Starship Century Symposium, a fun, imaginative conference dedicated to speculatively discussing humanity’s future among the stars. One talk I found particularly interesting covered “starships and the fate of humankind,” presented by Peter Schwartz During his presentation Schwartz showed a slide depicting human population projections through the next century. While I don’t remember specifically which projection Schwartz presented, it was broadly similar to one drawn from the 2003 UN Department of Economic and Social Affairs “World Population in 2300” report:
Schwartz described these three scenarios as the product of three possible stories. In the above forecast the “medium” line depicts a population growth rate similar to today’s, and by and large a continuation of the status quo: most women continue to have two children, and the global population neither grows nor shrinks. The “low” forecast predicts a future where society continues to grow richer, and families smaller. In this future women tend to have a fertility rate less than the replacement rate, and the human population shrinks, dipping below 3 billion by 2300. The final, “high” forecast is a more dramatic deviation from the status quo; the future fertility rate increases to and then holds constant at 2.35 children per woman, leading the human population to grow at an accelerating rate. In this future, barring any depopulating catastrophe, the human population tops 35 billion in the next 300 years.
Schwartz termed this scenario the “religious” future. Many global religions, and in particular fundamentalist interpretations, encourage high reproduction. Given that world fertility rates have dramatically fallen over the last half century, it is difficult to imagine a plausible scenario that would lead to a renewed increase in the fertility rate, given increasing female access to education and family planning techniques. However, a worldwide rebirth of religious fundamentalism that encourages adherents to pursue large families and grow the faith is perhaps the most plausible mechanism for a future global population growing at an accelerating rate.
There are other potential stories to explain the UN’s “high” scenario. In science fiction author Kim Stanley Robinson’s Mars trilogy, life-extending drug therapies are perfected before increases in worldwide human capital have put global society on the “low” trend, swelling the population — if people stop dying but don’t similarly stop reproducing, the population necessarily grows. But there are plausible reasons to believe Schwartz’s religious fundamentalism hypothesis is more likely. After all, a future global society filled with the same religious beliefs as today’s seems more plausible to contemporary forecasters than the sanitized, secular future predicted in the 1960s-vintage Star Trek franchise.
Additionally, an evolutionary logic could reasonably support the plausibility of this possible future. Since children are likely to, in the aggregate, inherit the religious beliefs of their parents, an individual’s religion can be viewed as an inherited trait. If this holds, religious traditions that encourage fecundity and religious communities that reproduce at a higher rate than the rest of society will grow to be a larger and larger percent of that population. While it’s reasonable to be wary of forecasts that require a dramatic change from the status quo — as this “high” population scenario does — there are plausible reasons not to discount this future. After all, is a dramatic future increase in the global fertility rate any less plausible than the last fifty years’ dramatic decrease, which few saw coming?
As I’ve previously written, I don’t see population growth as a viable road to human interstellar expansion. First, if the human population peaks this century as most forecasts predict, there will be little need for extraterrestrial lebensraum (read into that what you will) anyway. As I wrote last year:
“Even assuming huge technological advances dramatically reduce the cost of space transport and allow for robust off-world industrial infrastructure, costs of living away from Earth will always be unimaginably high. On Earth atmosphere and surface pressure are free; anywhere else they aren’t. If the world population peaks this century there likely won’t be any pressing demographic reason humans have to live off planet, and it is difficult to imagine any other incentive to leave that satisfies any plausible cost/benefit criteria.”
Finally, and more importantly, space travel is fundamentally a luxury. This is especially true for interstellar travel. Now, I don’t mean “luxury” to convey frivolity — but whatever the merits of extraterrestrial expansion, space travel is expensive. If global civilization suffering from the overpopulation-induced shortages, resource constraints, and catastrophes that would motivate expansion beyond Earth in the first place, humanity is unlikely to have the capabilities to do so, anyway. Given the costs of even one-off interstellar missions, this logic is a major barrier to the mid-term plausibility of involuntary interstellar migrations.
But Schwartz suggested another incentive for interstellar expansion in a high population, religious fundamentalist future: bringing the word of God to the alien heathens. Of course, there are some big leaps here — not only does this scenario require that humans eventually detect intelligent life, but that it is located close enough to our solar system that it’s reasonable to travel there. Additionally, this assumes convert-minded religious missionaries judge face-to-face contact with aliens, over simply transmitting them religious messages, to be worth the fantastic cost of interstellar spaceflight. Finally, this scenario also assumes that religious leaders judge aliens — who are likely to differ widely in appearance, outlook, and social structure from humans — to be worth converting. This is by no means assured, and it’s worth remembering that it took Christian religious figures decades to unequivocally decide that obviously-human Native Americans did in fact have souls.
Despite these cavets, a race between religions to spread their faith to aliens is an interesting concept (though these religious leaders would likely be much less enthusiastic about aliens spreading their own religious beliefs to us). But I can think of another, speculative, barrier to this possibility. Recent history’s most missionary religious sects tend to be the most apocalyptic, a tendency especially evident in Christianity and Islam, the world’s two largest religions largely due to their historical expansion. Recent polling by Public Policy Polling suggests that 11 percent of Americans believe the Rapture will occur within their lifetime, and nearly 60 percent of white evangelicals reportedly believe the Rapture is due before 2050. In a 2012 Pew study, in 9 of 23 Muslim countries more than half of those polled expressed the belief that the Mahdi will return within their lifetime.
If missionary impulses and apocalyptic thinking are linked, this suggests that the sects most likely to attempt to convert intelligent aliens also discount the future the most. Indeed, generations ships as a class are essentially predicated on very low discount rates, as only the distant descendants of their builders will ever benefit from their initial investment. This poses a major problem to interstellar missionary efforts. If you believe that the rapture will occur within your lifetime, launching a generation ship to convert aliens is literally pointless — the universe will likely end before the ship arrives! Indeed, if you believe that the end of the world will end in the next half century, it’s pointless even to attempt to communicate with aliens more than 50 light years away, relatively right next door!
Now, this of course doesn’t make interstellar missionaries impossible. But it’s worth remembering that religious impulses and spaceflight are likely to interact in ways difficult to predict.