Black swans over the Anduin; black butterflies above Mirkwood (and black squirrels inside it); black horses in Rohan; black Orcs -- Middle-earth is replete with dark or 'melanic' varieties of animal, generated or favoured by Sauron. The implication is that blackness is the livery of evil, a sign of the Dark Lord at work. But as with everything in Tolkien's world, matters are not quite as simple as they seem. Neither, as it happens, is the scientific research on the causes and inheritance of melanism.

All creatures vary in their habits and appearance. If this variance is heritable, then it follows that the environment can favour one kind of variant over another, and, in the course of time, the overall genetic complexion of a population of organisms can change. This is the essence of evolution by natural selection, as outlined by Charles Darwin in On The Origin of Species by Natural Selection in 1859.

One of the most popular and compelling examples of natural selection in action concerns the incidence of melanism. As long ago as 1896, one J. W. Tutt reported that a dark variety of a woodland moth, the peppered moth Biston betularia, was becoming more common at the expense of the normally prevalent speckled (that is, 'peppered') light-coloured variety. Tutt speculated that these nocturnal creatures, resting by day on tree trunks, gain protection from marauding birds by means of camouflage. Light-coloured moths would be able to hide, unseen, on lichen-covered bark, a background that would leave the melanic form dangerously exposed. Natural selection would ensure that the light-colored progeny of light-colored moths would gain the day. Melanic moths, in contrast, would be better hidden on soot-blackened bark, especially on trees where the lichen had been killed by industrial pollution. It was the observation of an increase in melanic moths in woods close to industrial centers -- driven by natural selection -- that prompted Tutt to advance this idea.

Tutt's hypothesis was repeatedly challenged in the ensuing decades, particularly by researchers who suggested that melanic moths might be darkened by virtue of diet: creatures fed as caterpillars with certain chemicals (such as might be found in industrial pollutants) might grow up darker than their fellows fed more wholesome fare.

It was at this point that the biologist Bernard Kettlewell enters the story, with a series of experiments designed to find out whether natural selection was responsible for the observed changes in the peppered-moth population. Kettlewell showed that dark moths on dark backgrounds were better hidden than light-colored moths on dark backgrounds (and vice-versa). He also observed aviary birds in the act of attacking moths at rest on branches. Taking these findings into the wild, he used mark-and-recapture experiments to show that light-colored moths do better than melanic in unpolluted woodland, and conversely that melanic moths survive better than light-colored ones in woodlands whose trees have been blackened by pollution.

This work has long been advanced as a 'textbook' demonstration of natural selection at work, and it is entirely possible that Tolkien could have been aware of it. Given Tolkien's upbringing and his constant equation of industrialization (and its attendant pollution) with the forces of evil, it is possible that he was attracted by the idea of melanism as a change that might be visited on organisms specifically as a result of industrial activity -- indeed, it was the idea of a particularly 'industrial' melanism, related to pollution, that had been suggested by Tutt and debated by subsequent workers, that might have caught Tolkien's attention. Whether organisms became melanic as a result of ingesting pollution, or less directly as a consequence of natural selection, would hardly have mattered to Tolkien -- to him, what would have been important would have been the connection between pollution and change in the organisms. This concept would have fitted very well with his idea that the Dark Lord cannot make organisms from scratch, but only make mockeries of them by corruption and perversion.

As an aside, Turgon draws my attention to Tolkien's first-hand encounter with industrial pollution while he was Reader in the English Department at the University of Leeds in the early 1920s. In those days Leeds was the epitome of an industrial city (when I was there as a student in the 1980s it was in deep decline, though now it has reinvented itself as a white-collar boom town.) In The Tolkien Family Album, John and Priscilla Tolkien report of life in 1921:

"Then they moved to 11 St. Marks Terrace, not far from the University, an area now demolished and built over. Then it was dingy and soot-covered. Chemicals in the air rotted the curtains within six months, and baby Michael was covered in smuts if he was left outside in his pram for any length of time; and Ronald found that he had to change his collar three times a day." (p. 45)

None of this means, of course, that melanism in Tolkien's fiction is automatically seen as a result of industry, or even of the workings of evil. The livery of the Numenoreans, especially those closest to the heart of the ancient realm -- the guards of the citadel in Minas Tirith, and Aragorn himself -- is very largely sable (that is, black). To take a less superficial case, the giant spiders with which no Tolkienian tale is complete -- Ungoliant, Shelob and the lesser creatures of Mirkwood -- consume light and produce darkness, but they are emphatically not the creations (or perversions) of industry, or of Morgoth or Sauron. They are independent entities antedating the corruption of Morgoth himself and are at best uneasy allies of the Forces of Darkness. It may be significant that the spiders themselves are always black -- there are no light-colored spiders for the Dark Lord to corrupt. The existence of the possibility of variation is as vital to the understanding of melanism in the real world as it is in Middle-earth: black creatures, whether swans, butterflies or squirrels, are remarkable only inasmuch as there are light-colored forms with which they can be contrasted. The same is true for peppered moths.

In recent years, the work of Kettlewell has been subject to vigorous reappraisal. New knowledge of the behaviour and genetics of moths has cast doubt on the validity Kettlewell's experimental results, and even on the premises on which the experiments were based. It seems that although there is a relationship between the incidence of melanics and the degree of sulfur-dioxide pollution, the connection between moths and lichens is much less clear-cut. Moths in the wild settle in a variety of places, not just tree-trunks, and the choice of settlement-site by Kettlewell's released moths might have been determined by the way Kettlewell did the experiment rather than the natural predilections of moths. In some isolated cases, the incidence of melanics or of light-colored forms of moth bucks the trend of industrialization. And it is always possible that melanism, which exists as a consequence of genetic variation, is favoured (or not) by natural selection acting on some other trait not directly connected with the color of the animal.

Given the prominence of the peppered-moth experiments as exemplars of evolution in action, some people have used various problems with Kettlewell's legacy as a means to discredit evolution (see, for example, an article by Jonathan Wells online here). However, this is as logical as saying that the telephone is inherently evil just because some people use it to make dirty phone calls. Although it seems clear that the picture is more complicated than was first thought, the fact remains that birds preferentially peck at visible moths, irrespective of wherever they are hiding; and that the general incidence of melanism rose with industrialization in the UK and fell with the enactment of anti-pollution legislation -- and did so independently in both the UK and the United States, where changes in the incidence of melanism in a relative of Biston betularia had also been documented. No evidence has been advanced to corroborate the old idea that melanism is a consequence of diet, so natural selection remains by far the best explanation (see Bruce S. Grant's article in, Evolution 53, 980-984, 1999).

Melanism remains a fascinating topic and a subject of intense debate more than a century after Tutt's initial speculations on the peppered moth. But Tolkien takes the topic of natural coloration further, with a single reference to flies in Mordor that bear the device of the Lidless Eye. It's in The Lord of the Rings Book VI, chapter 2 (The Land of Shadow):

"Flies, dun or grey, or black, marked like orcs with a red eye-shaped blotch, buzzed and stung; and above the briar-thickets clouds of hungry midges danced and reeled".

This mention --as casual as it is startling -- begs the question of how these flies could come to be so adorned. Did Sauron have workshops full of Orcs, each with a tiny paint-brush, decorating flies individually? This option is patently absurd. The answer is that the flies evolved the Eye. Many creatures, especially those liable to be eaten by visually oriented predators such as birds, adopt a warning coloration, conventionally of contrasting colors such as black and yellow. Others, however, go further by flashing spots or other features as a kind of counter-threat -- even if it is a bluff. The prominent eye-spots of certain butterflies and other insects can be interpreted in just this way -- as eyes that might disconcert a potential predator.

How do eye-spots evolve? Notwithstanding some work showing how eye-spots in butterflies can appear and disappear more or less spontaneously, it remains possible -- at least theoretically -- that a pattern of smudges or blotches can, over generations, take the form of eyes, or, indeed, of any shape most likely to deter predators. Creatures with the most eye-like blotches will, like melanic moths in a sooty forest, win the day. This tendency will even be sharpened by the increasing discrimination of predators, who will begin to appreciate ever-finer degrees of difference between more or less eye-like blotches. Given that the sign of the Lidless Eye is a cause of existential terror in the whole of Middle-earth, it is no wonder that those flies bearing this sign on their bodies should be the ones most likely to remain uneaten, and to settle on whatever carrion happens to be lying around in Gorgoroth.

-- Olog-Hai

The Science of Middle-earth, by Olog-Hai's very good (indeed, coextensive) friend Henry Gee, will be published in the United States on 1st November by Cold Spring Press, and in the UK in May 2005 by Souvenir Press. You can pre-order it now from Amazon.com. ISBN 1593600232 $14.00