By Light Alone

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Malthusianism is a topic that many science fiction writers have tackled, but the genre can not be said to have come out looking particularly good. The trouble is that the conventions of the genre require that a story must not raise a problem without solving it within the compass of the narrative, by some kind of heroic action. Here in the real world we know that reductions in fertility are associated with improvement in the status of women in society, and with their access to education, health care and contraception. For some reason, these topics have not appealed to science fiction writers, who have preferred to write about authoritarian restrictions on fertility,1 forced mass sterilization,2 and most commonly that old science fictional standby, genocide.3 The Science Fiction Encyclopedia sums up the genre’s approach to the topic of overpopulation: “Suggested solutions not involving mass murder are rare, and not usually to be taken seriously.”

Adam Roberts’ 2011 science fiction novel By Light Alone doesn’t fall into the obvious trap: his sympathies are with the teeming masses, and as a historian of science fiction he’s all too familiar with the trope. From his review of Sheri Tepper’s The Margarets:

The book proposes a sort of unreconstructed vulgar Malthusianism—the problem is over-population, the only solution is cutting back population—selling people en masse into slavery, neutering 90% of the population, even culling people: all these are unfortunate but acceptable strategies to allow the forests to regrow. […]

I think the novel is wrong on quite a basic level; and because this is core to what the book is doing (and because environmental degradation is a real and pressing problem) I think it a fatal sort of wrongness. Malthus noted that population increase outstripped increases in food production, and foresaw catastrophe in his own lifetime. It didn’t happen, because Malthus didn’t see that a larger population also provides a larger number of people to invent solutions to the problems posed by a larger population. Tepper also doesn’t see things this way. For her, people are a brute problem, to be solved by the intervention of gods and superpeople. […] Her disapproval is palpable and, really, pretty prudish. Nasty people and their nasty habits of having sex and filling the world up with people.

But the topic of overpopulation has more than one trap, and I think By Light Alone doesn’t steer clear of them all.

The background to the novel is that inoculation with a genetically engineered virus causes your hair to turn green and start photosynthesizing. If your hair is long enough and you live in the tropics, the energy gained from a day spent sunbathing is just about enough to keep you alive. This ought to be a boon that frees the poorest people from the need to grow food or work to buy it, liberating them to work their way higher up Maslow’s hierarchy of needs. But in a convincingly brutal application of Malthusian logic, Roberts describes how this invention enabled the population to grow to the point where it was limited by other factors than food (water, minerals, vitamins), and how it enabled people to accept lower wages for the same work, perpetuating their poverty.

If you’ve been following along with my reviews of Adam Roberts’ novels,4 you won’t be surprised that I got out my calculator at this point. The power of sunshine in a cloudless sky at midday is about 1,000 W m−2, but on average the insolation in the tropics is only about 30% of that. With photosynthesis working at an efficiency of, say, 10% (compare with sugar cane at 8% peak efficiency), in eight hours of sunbathing that yields about 2.4 MJ per m2 of exposed hair. When we compare this to the Food and Agriculture Organization of the United Nations’ minimum adult daily intake of about 7 MJ we can see that something has to give. Is 30% efficiency plausible? Is 3 m2 of exposed surface area of hair plausible? I don’t really find either adjustment completely plausible, but this is really not bad at all: to be within half an order of magnitude of plausibility is pretty much as good as it gets for a science fiction novel. (Use that as your pull quote, I dare you!)

However, the Malthusian logic that drives the plot is not so good. Roberts asks us to imagine that population fertility is so high as to push the population up against the limits of resources like potable water, but also so low (due to malnutrition) that people are desperate enough to kidnap the children of the rich—and not for ransom, but for more-or-less-worthless manual labour or sexual slavery. These two ideas are quite incompossible: the demographic equivalent of the space hose in Gradisil. (I suppose they could be true in different places at different times, but still, wouldn’t the net result be migration rather than kidnapping?) I don’t think this really affects the success of the book, but it’s a nit that continues to niggle.

So what traps does the book stumble into? Well, the first is that in any account of the distribution of wealth in the real world, the historical legacy of colonialism and racism is a vitally important part of the story. So when Roberts totally avoids the subject of race, it leaves a gaping hole in the book. It’s hardly believable that the autotroph/heterotroph distinction should have utterly supplanted all racial distinctions, or that the rich/poor divide could have been completely divorced from political history. This is especially uncomfortable because the description of the way the social system works—the accommodation to mass poverty—is really grim. Roberts never mentions the ethnicity of his characters, and his description of location are vague, but the hints that the people who are kidnapping children into sexual slavery are based in the Caucasus or the Middle East play into contemporary forms of othering.

The second trap is that although By Light Alone takes the form of an attack on the selfishness and blindness of the 1%, the viewpoint characters are mostly themselves members of that class, and so the reader’s sympathy is inevitably going to be drawn to them, especially in the circumstances of the novel. Roberts is a skilful depicter of character, and the opening chapters contain some quite repulsive specimens of privilege, but it is hard to make a character so vapid and ignorant that you don’t feel sorry for him when his daughter is kidnapped.5 Three quarters of the novel are devoted to life among the elite, and only one quarter to the rest of humanity. And even then, the description of the life of the green-haired majority is from the point of view of an outsider who has been thrown among them, and so gives little clue as to how they see themselves. So the poor remain ‘other’ as far as the novel is constructed, and the story draws on the same old overpopulation trope: fear by the rich of being swamped by the teeming masses. Surely this way of framing this issue is itself at fault and in need of criticism?


  1. ^ For example, Robert Silverberg’s Master of Life and Death.

  2. ^ For example, George R. R. Martin’s ‘Manna from Heaven’, collected in Tuf Voyaging.

  3. ^ Perhaps the most famous example being C. M. Kornbluth’s ‘The Marching Morons’.

  4. ^ If these reviews seem to have been rather critical, it’s not because I don’t like Roberts’ work (as if I would read and review so many of his books if I didn’t like them), but rather because the books provoke a critical response.

  5. ^ Having said that, the main character’s passivity in the face of bureaucratic inaction seems wrong to me. A rich person in this situation would be going through his contacts and thinking, who do I know who could put pressure on this person to act?