From: The Tale of the Three Little Pigments

The purple compulsion

The mad desire for purple. With these words, Pliny the Elder recognised the spell that the colour has cast from the earliest period of human history (perhaps as far back as 1750 BCE). There’s something about purple that invokes the most extreme behaviour in individuals and populations. Clothe a Roman Emperor in Tyrian purple and, crazed with power, he ‘bestride(s) the narrow world/ Like a Colossus’. At the other end of history, the era of modern dyes began in 1856 with Perkins’s mauve, the aniline derivative that became all the rage in the fashionable world of mid-century London. For much of history the ‘mad lust’ for purple could not be satisfied by shellfish of the genera Murex and Thais that yield the imperial pigment, nor by the chemistry that conjured dyestuffs from coal tar. Isaac Newton described the purplish colours at the end of the spectrum as indigo and violet. In its day indigo dye, from leguminous plants of the genus Indigofera, and the Brassicaceous woad plant Isatis, was second in value only to Tyrian purple. By an extraordinary twist of evolutionary fate, indigo and imperial purpurea are nitrogenous compounds that differ in molecular structure only by the latter’s inclusion of two additional bromine atoms. Lichens are another biological source of purplish dyes. The blue-red acidity indicator litmus, familiar from school science labs, is an example. The traditional cloaks, variously described as red, mauve or blue, worn by the women of Fishguard in Wales as they repulsed an attempted French invasion in 1797 are said to have been dyed with the litmus-like lichen pigment orchil.

According to Friedrich Nietzsche ‘in individuals, insanity is rare; but in groups, parties, nations and epochs, it is the rule’. An extreme example of purple-fuelled irrationality was the tulip mania that engulfed the Netherlands in the 17th century. Tulip flowers owe their colours to anthocyanins, comprising rutosides of pelargonidin, delphinidin and cyanidin and their acetyl derivatives. Charles MacKay’s famous 1852 Memoirs of Extraordinary Popular Delusions and the Madness of Crowds placed tulip mania firmly up there with the South Sea Bubble as an archetype of ludicrous herd behaviour. It forms the background to The Black Tulip, the novel by Alexandre Dumas (1850), which captures the febrile atmosphere of the period through harrowing accounts of the lynching in 1672 of the de Witt brothers by a baying mob, the obsessive quest of Cornelius van Baerle to win the prize for breeding the flower of the novel’s title, and the malicious madness of his jealous rival Isaac Boxtel. Dumas gives a rather clear description of the plant breeding strategy that would lead to what the tulip world considered to be ‘as chimerical as the black swan of Horace or the white raven of French tradition’. Life ultimately imitates art: after years of crossing and selecting progressively darker and darker purple lines, the Dutch grower Geert Hageman produced the variety ‘Paul Scherer’ in 1997, the nearest thing to a black tulip yet.

In 1759 Samuel Johnson wrote ‘The business of a poet is to examine, not the individual, but the species; to remark general properties and large appearances: he does not number the streaks of the tulip’. It takes a brave person to disagree with the good doctor; but in this case, I venture he is mistaken and has overlooked the deep insights into human obsessions and follies to be gained by considering tulip flowers and ‘the plum history of the color purple‘.

From: The Tale of the Three Little Pigments

The gold vexation

Too much of a good thing: among the fossil hominids described by Richard Leakey and colleagues is a partial skeleton of Homo erectus from Kenya showing pathological changes consistent with chronic vitamin A poisoning. It was suggested that hypervitaminosis symptoms were the result of a change in the dietary habits of H. erectus to include a high intake of animal liver. There is a long history of vitamin A poisoning among arctic travellers and fishermen who consumed the livers of polar bears, seals, husky dogs or flatfish.

Generally speaking, however, hypervitaminosis A is a rare condition. On the other hand, UNICEF estimates that more than 140 million pre-school children and more than seven million pregnant women, are seriously vitamin A deficient, precipitating over a million child deaths each year. Of the 118 countries affected, most are in Asia, sub-Saharan Africa and South and Central America. Vitamin A deficiency is a leading cause of child blindness in developing countries. It also limits growth, weakens the body’s immune system and increases mortality. The condition and its treatment have been understood at least as far back as the time of the classical Greeks, and possibly even the ancient Egyptians. Consume liver (or fish liver oil) is the answer. But what if, as throughout the developing world, these remedies are of limited availability, too expensive, or precluded culturally by adherence to a vegetarian diet?

The Golden Rice project was born as a response to this predicament. Rice grains, the main food source in many of the regions with endemic vitamin D deficiency, are low in β-carotene, a precursor of vitamin A synthesis. But rice leaves, like all green plant tissues, make plenty of β-carotene. There’s evidently a gap somewhere in the terpenoid synthesis pathway of rice grains, the consequence of genes being disabled during seed development. It turned out this blockage could be overcome by introducing genes encoding two enzymes of carotenoid biosynthesis: the synthetase that converts endogenous GGPP into phytoene; and a bacterial enzyme that introduces four double bonds into phytoene, completing the metabolic sequence leading to carotenes. It took years to get the system working with high efficiency but now there are varieties of rice, biofortified with golden carotenoids, to levels in excess of 30 μg g^-1 fresh weight, that amply meet the recommended dietary daily allowance for adequate conversion to vitamin A. By ‘introducing genes’ I mean, of course, using transgenics, which pitches Golden Rice straight into the ongoing stand-off between biotechnology and the Green Movement. This issue is complex, fast-moving and won’t be analysed here. Suffice to say that the scientists who conceived and realised the Golden Rice project really should be household names, respected for their brilliant work: Ingo Potrykus, Peter Beyer, Adrian Dubock, Peter Bramley. They were motivated to apply their deep knowledge and expertise to solve a humanitarian problem. What have their extremist opponents contributed? Tearing down fences and tearing up plants. And the politics of this is getting uglier. It’s now being suggested that online information warfare, conducted by state-sponsored hackers, is driving even further the wedge between the scientists and environmentalists who ought to be on the same side.

Meanwhile, the vitamin deficient wait, suffer and die.

From: The Tale of the Three Little Pigments

The green dilemma

Chlorophyll stands at the centre of some of the great global challenges of the age. Take the example of sorghum. It’s difficult to dispute the view that increasing sorghum productivity – by keeping the crop greener, for example – helps to improve the circumstances of the most disadvantaged people in some of the most difficult environments, and will contribute towards achieving United Nations Development Goals. But the strategy is burdened with socio-political complexities, centred on the need for a Doubly Green Revolution, to use the title of the influential book by Conway, and concerns about protecting the rights, knowledge and germplasm of indigenous peoples against biopiracy and agribusiness exploitation. Across the world we find the ideals of Green Revolution and Green Environmentalism in collision, a strange state of affairs when the two movements might be expected to be on the same side.

The history of the influx of physicists to the field of genetics in the middle of the last century and their influence on the birth of the molecular biology revolution is well documented. Rather less familiar is the story of the decades following the 1939-45 World War in which a generation of scientists (physicists, mathematicians and engineers, as well as biologists) chose to devote their skills to agriculture (these days they go into finance). A powerful influence was the exposure of ordinary people in the developed world, for the first time, to images of mass starvation on the television screen in the corner of the room. Paul Ehrlich’s apocalyptic best-seller The Population Bomb caught, and intensified, the mood of the age. Radical political movements in the West at that time also contributed to the motivations of the new agriculturalists. Above all, most of those who took this path thought they were doing something honourable and philanthropic. Surely devoting one’s professional life to defeating famine was the right thing to do.

From the perspective of the next century, this attitude looks at best naive and, when it comes up against the anti-technological politics of contemporary popular Green movements, positively shameful. Many of the original idealistic feed-the-world scientists are still in business but having to contend with sometimes bewildering and frustrating hostility from groups that ought to share their ideals. Among the serious consequences are stagnation of financial and societal support for open public-good crop research, driving more and more of this work into the private corporate sector. It is difficult to see how this will benefit the poor and disadvantaged. These developments are all the more vexing now that at last we are acquiring the tools to do the job. That these tools are technological (particularly biotechnological) is, to a large measure, the problem. To get them accepted by those who should benefit from agricultural progress needs trust. Lack of nuance and sensitivity on the part of agribusiness and governments, and a general failure of communication by a scientific community driven by the best intentions, can land the average green-sympathetic jobbing crop scientist with a crisis of conscience. Is she doing good or harm?

The following recently published books in part developed from the darnel project and have much to say about the origins of our food and how it has shaped the nature, history and prospects of humanity.

How and why humans have come to be in thrall to – maybe even enslaved by – grasses is the subject of The War Between Trees and Grasses.  Here’s an extract that introduces the story:
This book begins by asking where did the first forests come from, what does it take to make a tree and how has the tree life-form become refashioned by evolution as the terrestrial environment varied over geological time. The later arrival of grasses on the evolutionary scene was both a response to, and an agency of, new and potent environmental challenges – identified by the title of this book, with only a slight degree of melodrama, as a declaration of war. Much later, evolution propelled Homo sapiens into the midst of the age-old conflict between grass and tree, a conflict that rages to this day and which…has shaped the nature of human psychology, physiology and culture.

Here’s a paper summarising the argument that the primaeval grass-tree confrontation played a decisive part in human evolution.
H Thomas. 2017. A green epoch in the evolutionary history of biological energy sources. Nature Ecology and Evolution 1: doi:10.1038/s41559-017-0302-8

The most recent book is The Tale of the Three Little Pigments. It concerns the colours of the natural world and in particular the ways that plants and light interact and influence human needs and behaviour. Extracts from the book will be posted on this site subsequently.

Books by Howard Thomas are available in Europe from AmazonUK and worldwide from Summerfield Books.