No Galactic Civilization for You

A recent video by Kurzgesagt asked if modern physics supplied a boundary, an absolute limit, to human expansion into the universe. The answer, apparently, is “yes:” humans cannot travel* beyond our own Local Group of galaxies, because “dark energy” propels other galactic clusters away from us at velocities too great to match. If lightspeed imposes an upper limit on spacecraft – and it must, because faster-than-light objects propagate backward in time, violating causality – we can explore our galaxy and Andromeda and a couple of dozen nearby dwarf galaxies, but no further.

The author presented this as a sad story, from the standpoint of a future “Type III Civilization” that has colonized and exploited the entire Milky Way galaxy. Permit me to say, though, that we twenty-first-century primitives need not mourn, because even creating a galaxy-spanning civilization probably lies beyond humans' capacity. We may develop the means, but I doubt we will ever have the motives to colonize an entire galaxy, let alone the rest of our Local Group.

Sci-fi writers, and historians, have adduced several possible motives for interstellar colonization, none of which seems likely to push us all the way through the Milky Way (100 billion star systems, remember) except perhaps in a distant, post-human future. Let us look in this post at one of them: population growth.

Overpopulation sounds like a reasonable motive for extra-solar colonization, especially when one realizes how rapidly human population has grown in the past couple of centuries – from one billion people in 1800 to more than seven billion today. SF writers like Harry Harrison and Larry Niven, and nonfiction authors like Paul Ehrlich, opined in the 1960s and '70s that the global population was headed for the 20 or 30 billion mark, and that war and famine would necessarily result. Since then, however, human fertility rates have declined, not for Malthusian reasons but as a result of economic growth in poor countries. In a modernizing, industrializing country, it makes more economic sense to have fewer children and educate them than it does to have many untrained children to work in the fields or mines. Smaller families also make more practical sense when access to modern medicine relieves couples of the need for “replacements” for those who die, and when birth control gives women more reliable control over their own fertility.

We have no reliable way of predicting fertility rates in the future, but we can speculate based on historical evidence from the last few thousand years. On that basis high population growth looks more like an anomaly than an inevitable trend. It usually resulted from innovations in food production and medicine, like the adoption of American crops in Europe and China in the seventeenth and eighteenth centuries, the development of medical antisepsis and antibiotics in the early twentieth century, and the “Green Revolution” in agriculture later in that century. More common is slow growth or stasis,** punctuated by crashes that wipe out several centuries of growth, like the epidemics that beset the early-modern Americas. I think it unlikely that we'll have another pandemic on the scale of the Black Death, but I do note that there are quite a few industrial countries that are losing population to parents' practical economic decisions: Japan, Russia (though poor health is also to blame there), and much of western Europe. Growth is leveling off in formerly underdeveloped nations like India and China. Within the next century, I suspect that the world's demographic growth rate will regress to the historical norm: slow to nonexistent. (The “hockey stick” of demographic growth will, in short, prove part of a sigmoid curve.)

In the longer term, we may see occasional population spurts like those mentioned above, but human historical trends and technological advances both militate against sustained high growth. Short-term growth episodes may eventually leave planet Earth with 20 or 30 billion people, but not for several more centuries. By then, humans should have found ways to house those people here on Earth: constructing denser and more livable cities, environmentally re-engineering desert or tundra for human settlement, and/or building artificial islands and reclaiming land from the sea. Further forward in the future, we will probably find ways to render some of the other worlds in our Solar System, like Venus and Mars, inhabitable by human beings.***

Or, by then, more imminent disasters than population growth will have destroyed us and our works. More on those in another post.

* Technically, spacecraft can travel outside the Local Group, but they cannot reach other galactic clusters – only empty intergalactic space.

** In medieval and early-modern Europe, for instance, any multi-generational population growth at all was considered high.

*** This assumes that space travel becomes as inexpensive in the future as trans-oceanic travel became in the eighteenth and nineteenth centuries, the heyday of global travel and colonization.

Them Bones: The Great Old Ones

(For the previous entry in this series, click here.)

Them Bones, 40-41, 44-46, 65-69:

After spending a few days in Took-His-Time's village, Madison Leake decides it will make a good place to wait for his fellow time travelers, and settles in for a long stay. He hides his carbine, trades in his uniform for a breechcloth, and begins accompanying Took on his fishing trips to the river. During one of these, Took, using a fishing spear tipped with three copper barbs, manages to kill a giant river creature of some kind. Canoemen bring the body ashore: it is a manatee, broad-flippered and flat-tailed, a lily pad still drooping from its bristled mouth. (Nice touch, that.) Madison notes that manatees had nearly gone extinct in his time, even before the nuclear war. Back in the Mississippian era, they are plentiful.

Waldrop identifies himself as a science fiction writer, but many of his stories don't seem to match the genre's archetypes; almost none feature space travelers, galactic empires, or aliens. Like mainstream SF writers, however, Waldrop knows how to evoke what the fans call “a sense of wonder,” in this case the wonderment one feels at seeing the dead come back to life. The homely details that Waldrop provides about manatees and passenger pigeons, and for that matter the awkward birds in his famous story “The Ugly Chickens,” make these lost creatures resonate with our senses, and impart life to them. Many's the story written about nostalgia, about longing for a vanished past, but few are the authors who can make us nostalgic for vanished species.

The novel returns to this theme a couple of chapters on, when winter arrives in northeastern Louisiana, and with it the first snow, “tick-tick[ing]” (65) on the walls of the huts, blanketing the town. Hamboon Bokulla and Dreaming Killer come to Took's house early that morning with bad news, though Leake doesn't understand what they're saying in such rapid-fire fashion. He nonetheless agrees to accompany the three men to the northwest, past frozen pools and snow-covered trees, four kilometers from his home village. The quartet eventually arrive at a small farming hamlet whose houses and fields have been torn up by something unseen. Took confers with the villagers, then he and Madison and their compadres follow a huge set of footprints to the west.

The group reaches the cause of the disturbance: “A mountain made of hair,” twelve feet high, with protruding tusks and trunk, “tar-drop eyes” (68), and a trumpeting call like a giant tuba. Took addresses the “old one” (67), and bids him depart, lest he capture its spirit with the pipestone he carries. (Clearly, pipes represent powerful items, presumably because they bridge the earthly and spiritual realms.) The creature regards Took and Leake with an enigmatic expression, perhaps weariness, then, very slowly, heads off to the west.

This scene requires a bit of license on Waldrop's part, as we have no evidence that wooly mammoths survived in North America, or anywhere else, into the fourteenth century. Dreaming Killer does say of the colossus “Not many of those left,” but there probably shouldn't be any. On the other hand, Waldrop is beginning to indicate that there are some elements of his Mississippian setting that differentiate it from the real thing, such as pipestone makers that know Greek, and (as we shall see) eccentric tornadoes.

Coming next: Did someone say "eccentric tornadoes"?