EVOLUTIONARY THEORY IS MOST commonly described in the catchphrase ‘the survival of the fittest’, which implies a degree of competition and lack of co-operation. The curious thing about dung beetles is how, in their evolutionary niches, they have both a combative and a co-operative existence. On any pile of fresh rhino dung, the array of dung beetles is mind-boggling, from the tiniest ones barely visible to the naked eye, to the large ball rollers. It is the collective activity of the different beetles, all working in their specific niches, which ensures that the large pile of dung is rapidly processed.

Ulisse Aldrovandi thought that insects could be described as atoms, because they were so tiny. Five hundred years later this analogy is most appropriate, as we know from the splitting of the atom quite how powerful very small entities can be. Insects are no different: a plague of locusts can destroy fields of food crops; a colony of termites can consume an entire tree and transform dry earth; a hive of bees can make the difference between a productive and a virtually dead orchard. We also know from the previous chapters what happens when a little settler arrives on a foreign shore and transforms life in the way that the dung beetles did in Australia. As we have previously stated, if there were no dung beetles then there might have been no human race, because the levels of disease and faeces on the planet might have led to our demise before we really got going as a new species.

Together with earthworms and ants, dung beetles represent a trinity of earth transformers. They literally change the earth beneath us, and they do so at absolutely no cost to us. We have only begun to start understanding them, and although less curious minds might think that everything that needs to be said about them has already been covered, there is still so much we do not know. We do not know, for example, if all the species have been accounted for; we do not really know how they came to arrive in places like Madagascar, or indeed in many other countries. We do not know why some species are such generalists while others have very narrow geographic ranges and food choices.

DEATH IS NOT A SUBJECT one expects to find at the beginning of a book on dung beetles. The idea of someone's great-great granny wandering around with dead dung beetles dangling from her ears is equally strange, but the two subjects are not unrelated. The Victorians in their grand obsession with Egypt, death and loss shared a number of ideas with the ancient Egyptians from whom they took the association of dung beetles with death. The difference in the case of the Victorians was that they had a monotheistic religious template for death, which differed from the Egyptians’ rich animist pantheon of gods. Moreover, instead of wearing scarabs made out of stone, the Victorians frequently wore the real thing. Quite how the hapless beetles found themselves adorning the earlobes of respectable ladies is part of a story that began seven thousand years ago in Egypt, and which came full circle with the nineteenth-century invasion of Egypt by Napoléon and the subsequent development of Egyptomania. It was the two subjects of death and resurrection that made dung beetles so significant in ancient Egypt.

Although the family of dung beetles comes in a huge array of sizes, bizarre shapes and iridescent colours (with some so small you can barely see them) it is the smaller subfamily of true dung beetles that earned these insects their central role in Egypt. What made them so important to the Egyptians was their intimate relationship with dung, which promoted them to godliness. This makes the idea of dainty/fastidious Victorian women boldly wearing such creatures as ornaments seem even odder. The Victorians, however, viewed dung beetles and nature in general as a window onto the mystery of creation and as a distraction from the ugliness of industrial society, so perhaps they did not consider the faecal associations of their entomological jewellery too closely. The same cannot be said for the ancient Egyptians, who were very aware of the dung-rolling proclivities of the beetles. It is this improbable and intriguing relationship between an insect known for its relationship to ‘filth’ and the beliefs of one of the most enduring civilisations known to humankind that is our point of departure.

WHEN THE EGYPTIA NS ELEVATED the humble dung beetle to a symbol of transformation, they were part of a long process of change in the course of human beliefs. We moved from being animists (where each object was imbued with its own spirit) to being theists, where power was held by a limited number of deities and brokered by a priesthood that mediated access to those gods. That journey (from imagining how the earth came into being, to accepting that all life is composed of the same genetic material) has brought us to the point of understanding that we share a common origin with dung beetles and every other living organism on this earth. How that common ancestor has evolved into a myriad different creatures is a fascinating and constantly expanding field of enquiry, and our indomitable little friends are helping us to find the answers to some of those questions.

Dung beetles have become one of the pivotal species’ groups in modern evolutionary studies because, small though they are, they are helping us to begin understanding how variation within a species (in horn size, for instance), could promote speciation, which has resulted in so many diverse species in this case. Those 6 000-plus species are found in at least 257 genera (the plural for genus, the next grouping in the classification hierarchy in which species are nested); compare this to humans, where we are only one species (sapiens), sitting alone in our solitary genus (Homo), with all of our relatives extinct. The transformation dung beetles are now helping us to understand is one of speciation: in other words, how one species can give rise to another.

These recent findings go a long way to resolving Charles Darwin's issues with his own theory of evolution. Darwin had Mendel's discoveries of the mechanisms of inheritance on his own bookshelf, unread; if he had read them, he could have explained the problem of the blending of parental characteristics in their offspring (that over time, this would remove variation from any population, thereby leaving natural selection nothing to work on). In the same way, Darwin came tantalisingly close to an explanation of how new species could arise when he used dung beetle horns as examples of a sexually selected characteristic in The Descent of Man, and Selection in Relation to Sex (1871).

IN THE SUMMER OF 2009, one of us (Byrne), at least, was having fun. He was in the bush with his friends, playing with dung beetles. These friends, a group of scientists from Sweden, Australia, Germany and South Africa have managed to get together every year since 2003 to run experiments on dung beetle orientation.

We had already shown that dung beetles were the first animals known to be able to orientate by polarised light from the moon. Our next task was to measure how the nocturnal species performed when compared with their diurnal (day-active) counterparts. This involved working all day and most of the night when the moon was in a particular phase, getting slimmer as it waned into a silver sliver lying on its back in the African sky. We were tired but happy. The nocturnal beetles were incredible; they could roll their dung balls in a straight line under a cat's whisker of a moon.

But when the moon was absent and we relaxed, drinking cold beer under the light of the Milky Way, we were fixated with the sky. If we could see this ethereal light, then surely the beetles could too, and therefore use it for orientation? At the time only humans, along with a few species of birds and seals, were known to be able to orientate by the stars. Our beetle companions were a (relatively) large, enigmatic ball-rolling species called Scarabaeus satyrus. We knew they could do it, but needed to prove it with scientific rigour. The key challenge was to stop the beetles looking at the sky, which is equivalent to asking a goldfish not to swim. How does one stop a beetle looking at the sky? Not so difficult if you fit it with a little peaked cap. But not that easy either when it has no ears to hook things onto, and its head is flat and shiny and has evolved to stop anything sticking to it.

Nevertheless, once their hats were glued precariously in place, the capped beetles were lost, wandering aimlessly with their dung balls, all dressed up and nowhere to go. Ten minutes earlier, the same uncapped individual had streaked across the starlit savanna with the confidence of a taxi driver heading for home.

THE AUSTRALIA N DUNG BEETLE story is largely attributable to a successfully orchestrated and thoroughly researched biological solution to an imported problem. It was Australia's good fortune that George Bornemissza arrived from Hungary when he did, and was able to prove the practicality and efficacy of dung beetles. He ran against the trend of the post-war tendency to reach for quick, cheap and apparently effective solutions. Dung beetles, despite proving themselves to be relatively adaptable little transformers of the earth, were unable to keep up with the excitement of a world in which it was possible simply to sprinkle an almost magical dust known as DDT (dichloro-diphenyltrichloroethane) to end the life of an unwanted insect. With a limited understanding of how the natural world functioned, most insects were seen as problematic; differentiating between beneficial insects and harmful ones was not particularly high on the list of concerns of farmers driven to produce ever-increasing volumes of food.

The world at the end of the Second World War was a dismal time for insects: the myriad species of useful insects suffered as much as the few detrimental ones because DDT and the other new poisons did not differentiate between them. DDT is a member of the chlorinated hydrocarbon group. It was first synthesized in 1874, but its effectiveness as a pesticide was discovered only in 1939. During the Second World War, it was used for everything from delousing prisoners to controlling malaria. It was inevitable that following that war, DDT was regarded as the new wonder solution to insect pests. It was cheap, versatile, initially very effective and its residues kept the pests away for an extended period. Looking at only one country's consumption of DDT gives an idea of the scale of its usage. Up until 1972, approximately 1 350 000 000 pounds (or 675 000 tons) of DDT were used in the US, making it one of the most widely used pesticides in that country.

Biological control compared to DDT was simply too slow, but then an odd development gave the users of DDT and other pesticides pause. Farmers started to notice a resurgence in the numbers of pests where they had been spraying, accompanied by the worrying appearance of new pests that had never previously been present.

THE INCREASING SCIENTIFIC INTEREST in dung beetles was fuelled by both the burgeoning scientific industry (with biology diversifying into a multitude of new fields, from invasion biology to genetic engineering) and by the usefulness of dung beetles in our explorations of these new fields. Two characteristics of dung beetles have made them stars of the new biology: first, there are lots of them – over 6 000 species, offering a huge variety of already named species on which to test new ideas; secondly, they are incredibly compliant. Dung beetles, whether in captivity or the wild, get on with their lives regardless of who is watching or manipulating their small world. This makes them perfect subjects for studies of animal behaviour, in which we can ask questions of a simple animal and get straightforward answers, which in turn inform our understanding of how other organisms (including ourselves) perceive the world.

Why do animals move? For what purpose? The world is full of animals with which we share common spaces. Most of those animals move, apparently with reason or purpose, leading us to wonder what they are up to. These questions are at the core of the study of animal behaviour which, despite being an ancient human activity, is considered to be a relatively young science. Nevertheless, being formalised as a science under the rubric of ‘ethology’ by French biologist Isidore Geoffroy Saint-Hilaire (1805–1861) gave credibility to the careful observation of nature often provided by enthusiastic collectors. Darwin treated behaviour (along with structure) as a characteristic subject to natural selection, which could therefore influence an organism's chance of survival and reproduction. Unfortunately, Saint-Hilaire chose a word deriving from ‘ethos’ (from the Greek for ‘moral character’) and with a history of other meanings. Seventeenth century actors who portrayed human characters on stage were known as ethologists, while John Stuart Mill used the word ethologists to describe those who studied ethics. The name ethology has nevertheless stuck, and is used to describe the study of the behaviour of animals in their natural habitat.

Fabre (despite his rejection of a Darwinian interpretation of why the natural world looked the way it did) made important contributions to the infant science of ethology through his detailed observations of the behaviour of dung beetles and other insects, including bees and wasps.

THE FORTUNES OF DUNG BEETLES in the Middle Ages are relatively muted, and their main use appears to have been in remedies used by peasants. It was at the intersection of the Middle Ages and the Renaissance that the beetles began to reappear in the work of naturalists interrogating the heady mix of religion, alchemical pursuits and traditional knowledge of the previous thousand years. This small band of individuals frequently oscillated between alchemy and observationbased knowledge – hardly exceptional, given that there never is a clear break between historical periods. The word alchemy itself was derived from the Arab word ‘alchimia’ and referred to magical and mystical traditions combined with investigation into the nature of the physical world; it encompassed the very fluid boundaries between those activities.

Despite official injunctions against magic, magical formulas were as prevalent in medicine as they were in alchemical formulas for transmuting base metals into gold. Such formulas appear in the materia medica (collections of information about the therapeutic properties of anything used for healing) of the Middle Ages, scattered among the more prosaic use of flora and, to a lesser extent, fauna. The actual recording of the use of animals and insects in the West can be traced back to Xenocrates of Aphrodisias, a first-century Greek whose work is only indirectly known via the writings of Galen (circa 130–210). Xenocrates's influence spread to the Arab world, and it is in the Syriac Book of Medicines that we find a very medieval fate for black scarabs – they were boiled in olive oil to cure earache. Dung itself (without any attendant beetles) featured far more widely in medical concoctions in the Middle Ages, often in the form of bizarre mixtures which worked best (if at all) as placebos.

In China, dung beetles appear in early materia medica, and are still used today by practitioners of traditional Chinese medicine. These traditions began in rural areas, where peasants used whatever materials were at hand to effect cures. Some of these proved efficacious, and were recorded. Contemporary research in entomotherapy and compounds shows that different Chinese scarabs and their larvae have potentially useful antioxidant, antifungal, anti-viral and even anti-cancer properties, which probably explains why their use has continued for so long.

Footnote 4 to Chapter 21 in Darwin's Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world in which he makes reference to several species of dung beetles, along with his thoughts on how some species had arrived in particular places, while they were notably absent from others.

Among these few insects, I was surprised to find a small Aphodius (nov. spec.) and an Oryctes, both extremely numerous under dung. When the island was discovered it certainly possessed no quadruped, excepting perhaps a mouse: it becomes, therefore, a difficult point to ascertain, whether these stercovorous insects have since been imported by accident, or if aborigines, on what food they formerly subsisted. On the banks of the Plata, where, from the vast number of cattle and horses, the fine plains of turf are richly manured, it is vain to seek the many kinds of dung-feeding beetles, which occur so abundantly in Europe. I observed only an Oryctes (the insects of this genus in Europe generally feed on decayed vegetable matter) and two species of Phanaus, common in such situations. On the opposite side of the Cordillera in Chiloe, another species of Phanaus is exceedingly abundant, and it buries the dung of the cattle in large earthen balls beneath the ground. There is reason to believe that the genus Phanaus, before the introduction of cattle, acted as scavengers to man. In Europe, beetles, which find support in the matter which has already contributed towards the life of other and larger animals, are so numerous, that there must be considerably more than one hundred different species. Considering this, and observing what a quantity of food of this kind is lost on the plains of La Plata, I imagined I saw an instance where man had disturbed that chain, by which so many animals are linked together in their native country. In Van Diemen's Land, however, I found four species of Onthophagus, two of Aphodius, and one of a third genus, very abundant under the dung of cows; yet these latter animals had been then introduced only thirty-three years. Previously to that time, the Kangaroo and some other small animals were the only quadrupeds; and their dung is of a very different quality from that of their successors introduced by man.