But that was not the end of the affair, for a real-life Sherlock Holmes, a specialist in the anatomy of vision from Uppsala University, had an alternative hypothesis for what had led to the accident. Frithiof Holmgren suspected that the reason for the unexplained behavior of the northbound train was that the driver or the engineman, who had been overheard shouting something to the driver as they were speeding out of the station, mistook the red stop light for a white go light because he had some form of color blindness. Both the driver and the engineman died in the crash, so the suspicion could not be verified directly. And needless to say, the railway authorities flatly denied that any of their employees could have had a problem distinguishing the colors of the signs without it having been detected earlier. But Holmgren persisted and finally managed to persuade the director of one Swedish railway line to take him along on an inspection tour and let him test a large number of personnel.
Train crash in Lagerlunda, Sweden, 1875
Holmgren had devised a simple and efficient test for color blindness that used a set of some forty skeins of wool in different hues (see figure 2). He would show people one color and ask them to pick up all the skeins of similar color. Those who picked unusual colors, or even just unduly hesitated in their choice, would immediately stand out. Of the 266 railway workers Holmgren tested on just one railway line, he found thirteen cases of color blindness, among them a stationmaster and a driver.
The practical dangers of color blindness in an age of a rapidly expanding rail network thus became acutely apparent, catapulting color vision to a status of high public priority. The subject was rarely out of the newspapers, and within a few years governmental committees were formed in many countries, leading to mandatory testing for color blindness among all railway and marine personnel. The climate could not have been more favorable for a book which implied that latter-day color blindness was a vestige of a condition that had been universal in ancient times. And this was exactly the theory proposed in Hugo Magnus’s 1877 treatise on the evolution of the color sense. What Gladstone’s groundbreaking chapter never managed in 1858 (most people never got beyond the second volume, and the chapter on color was hidden at the end of the third), what even Geiger’s rousing lecture failed to accomplish in 1867, Magnus and the Lagerlunda train crash achieved ten years later: the evolution of the color sense turned into one of the hottest topics of the age.
Magnus’s treatise purported to provide the anatomical nuts and bolts, or rather nerves and cells, to Gladstone’s and Geiger’s philological discoveries. The perception of the ancients, Magnus wrote, was similar to what modern eyes can see at twilight: colors fade, and even brightly colored objects appear in indefinite gray. The ancients would have perceived the world in this way even in full daylight. To account for the refinements in the color sense over the last millennia, Magnus adopted the same evolutionary model that Gladstone had relied on two decades earlier, that of improvement through practice. The retina’s performance, he argued, “was gradually increased by the continuously and incessantly penetrating rays of light. The stimulus produced by the unremitting pounding of the ether particles continually refined the responsiveness of the sensitive elements of the retina, until they stirred the first signs of color perception.” These acquired improvements were inherited by the next generation, whose own sensitivity was further increased through practice, and so on.
Magnus then combined Gladstone’s insights about the primacy of the opposition between light and dark with Geiger’s chronological sequence for the emerging sensitivity to the prismatic colors. He claimed to know why the sensitivity to color started with red and progressed gradually along the spectrum. The reason was simply that the long-wave red light is “the most intense color,” the one with the highest energy. The energy of light, he said, decreases as one progresses along the spectrum from red to violet, and so the “less intense” cooler colors could come into view only once the retina’s sensitivity considerably improved. By the Homeric period, the sensitivity had got only to around yellow: red, orange, and yellow were fairly clearly distinguished, green was only beginning to be perceived, whereas blue and violet, the least intense colors, were “still just as closed and invisible to the human eye as the ultra-violet color is today.” But the process continued in the last few millennia, so that gradually, green, blue, and violet came to be perceived just as clearly as red and yellow. Magnus hypothesized that the process may still be ongoing, so that in future centuries the retina will extend its sensitivity to ultraviolet light as well.
Magnus’s theory became one of the most ardently discussed scientific questions of the day and received support from a range of prominent figures in different disciplines. Friedrich Nietzsche, for instance, integrated the color blindness of the Greeks into his philosophical edifice and drew from it fundamental insights about their theology and worldview. Gladstone, now an ex-prime minister and at the height of his fame, was gratified to find a scientific authority so enthusiastically championing his findings of twenty years earlier and wrote a favorable review in the popular journal
The claim that the color sense evolved only in the last millennia also received a considerable amount of support from eminent scientists, including some of the brightest luminaries in the evolutionary movement. Alfred Russel Wallace, the codiscoverer with Darwin of the principle of evolution by natural selection, wrote in 1877 that “if the capacity of distinguishing colours has increased in historic times, we may perhaps look upon colour- blindness as a survival of a condition once almost universal; while the fact that it is still so prevalent is in harmony with the view that our present high perception and appreciation of colour is a comparatively recent acquisition.” Another stellar convert was Ernst Haeckel, the biologist who had proposed the theory that an embryo recapitulates the evolutionary development of the species. In a lecture to the Scientific Club of Vienna in 1878, Haeckel explained that “the more delicate cones of the retina, which impart the higher color-sense, have probably developed gradually only during the last millennia.”
Looking back at Magnus’s theory from today’s vantage point, we cannot but wonder how such eminent scientists could have failed to pick up on the various rather odd things about it. But we have to put ourselves in the mind-set of the late nineteenth century and remember that much of what we take for granted nowadays, for instance about the physics of light or the anatomy of the eye, was a complete mystery to scientists just over a century ago. The distance between us and Magnus’s contemporaries is even greater in all that concerns knowledge of biological heredity, or, as we call it today, genetics. And, since heredity is the pivot of the whole debate over language’s place between nature and culture, if we are to understand this debate, we need to pause for a moment and try first to jump over the gap of imagination that separates us from the 1870s. This task is far from easy, since the gap is about as long as the neck of the giraffe.
We are all acquainted with the logic of “just so” stories: the giraffe got his long neck because his ancestors stretched and stretched to reach higher branches, Kipling’s elephant got his long trunk because the crocodile pulled his nose until it stretched and stretched, and Ted Hughes’s lovelorn hare got his long, long ears from listening and listening, all through the night, for what his beloved, the moon, was saying high in the sky. Today’s children realize at a fairly early stage that all this is only fireside fable. The main reason why the logic of such stories is confined to the nursery is a truth so universally acknowledged that hardly anyone even bothers to state it explicitly nowadays. This is the understanding that physical changes you undergo during your lifetime will not be passed on to your offspring. Even if you do manage to stretch your neck, like the Padaung women of Burma with their neck rings, your daughters will not be born with longer necks as a result. If you spend hours on end lifting weights, this will not make your sons be born with bulging muscles. If you waste your life staring at computer screens, you may ruin your own eyes but the damage will not be passed on to your children. And training your eye to recognize the finest shades of color may make you a great art connoisseur, but it will have no effect on the color vision of your newborn offspring.
But what-to paraphrase Gladstone-every child in our nurseries knows today was not even remotely obvious in the nineteenth century. In fact, the inheritance of acquired characteristics wasn’t classed as fairy tale until well into the twentieth. Today, under the bright neon light of the genetics lab, when the human genome has been mapped, when scientists can twiddle their pincers to clone sheep and engineer soybeans, and when children learn about DNA in primary school, it is difficult to imagine the complete darkness in which even the greatest minds were groping just over a century ago in all that concerned life’s recipe. Nobody knew which properties could be inherited and which could not, and nobody had any idea about the biological mechanisms that are responsible for
