by Martin Jones
These animal stories add another dimension to our understanding of farming beginnings. Plant and animal domestication have often been treated as part of a single process, an idea reinforced by the coexistence of so many precursors of major world crops and livestock in a single region, the Fertile Crescent. The DNA evidence separates them a little more. In both cases, the pattern of domestication is patchy in space and time, but with animals the situation is more dispersed still. Virtually every animal domesticate so far examined through DNA methods would appear to be the consequence of multiple domestication highly dispersed in space and possibly time. The domestications of dog, cow and horse were processes scattered across entire continents, a far cry from the single-centre accounts.
Something else can be said about these last three animals. Their domestication did not just influence humans through the food in their stomachs, but also changed their mobility. Dog, cow and horse each allowed humans to travel vast distances together with sizeable loads. They could pull a sledge or cart, and the larger ones could pull or carry people as well. The control of animals as well as plants initiated a new set of journeys, leaving yet another series of molecular tracks in their path.
afterword
Among the very large number of animal taxa that have been explored through ancient biomolecule research, the one that enjoyed a singularly iconic relationship with the field is the woolly mammoth. As well as standing as a conspicuous symbol of extinction, its big bones and teeth, found in very cold contexts, are ideally suited to molecular recovery. In the early days of ancient DNA research, a number of the pioneers, including Hagelberg and Pääbo had successfully identified mammoth sequences, and had begun to reveal the taxon’s lost genetic diversity. By 2007, Ian Barnes and colleagues were able to move that analysis significantly forward, on the basis of a genetic evidence from forty-one mammoths, all but a handful of which derived from the Northern Arc. Those forty-one mammoths revealed a genetic tree with clear bifurcations into distinct regional populations. Six years later, a study by Eleftheria Palkopoulou and colleagues could draw upon over 300 individual mammoths. The branching tree made sense the context of a radically changing climate. In good times, the big beasts could spread substantially across the globe. In bad times, their populations would tumble, and segregate into geographically isolated groups whose genetic fingerprint is still recoverable in these remains.
In the very dynamic population histories now being assembled from modern and ancient genetics, the possibility of extinction was never far away. A diminutive form of woolly mammoth lingered on in the Siberian Arctic on Wrangel Island until around 4,000 years ago. By this time, the big beasts that were fairing best in the climatic fluctuations of the Quaternary world were those whose had become most intimately entangled with the fates of humans, through the process we have labelled ‘domestication’. The analysis each of these domesticates has greatly progressed along parallel lines to the mammoth research, with larger samples sizes, earlier dates, and genome-wide analyses. We can take as an example the horse.
The ancient DNA information for the horse was now tracking back three quarters of a million years. The antiquity of the Thistle Creek horse introduced in the first chapter’s afterword is greater than the entire history of horse domestication by a factor of a hundred. It is moreover twenty-five times as old as the most ancient horse bones available to the pioneering study by Lister and Stanley. In Ludovic Orlando’s study, this very ancient sequence was compared with that of more recent specimens. A second ancient horse from the Taymyr Peninsular, while at 43,000 years old was considerably younger, it was still considerably earlier than the era of domestication. Alongside these, a donkey, a Przewalski horse, and five domesticated horses made up the modern comparative sample.
Drawing upon these to follow patterns of evolution over the last three quarters of a million years, the phylogenetic tree displayed episodes of increased branching, alternating with bottlenecks and episodes of population fragmentation, rather like the mammoth. With a refined molecular clock, these fluctuations could be aligned with Quaternary climatic fluctuations, and the perils of being large in a fast-changing environment become directly visible and measurable, providing ecological context and texture to the early spread of wild horses from America, and the then boom-bust history in the Old World. At successive downturns, corresponding to shrinkage of grassland habitats, population collapses by a factor of two, eight, or for the most recent down, a brutal factor of 100 may be calculated. Orlando’s results also indicated from a population fragmentation prior to this last collapse that Przewalski horses were isolated as a side branch; these rare animals are not wild ancestors after all, but cousins.
By comparing the Thistle Creek horse with more recent horses, it became possible to recognize parts of the genome in which diversity in domesticated horses is especially narrow. The kinds of protein those regions are making, and what ecology and behaviour they are instigating could also be determined. In twenty-nine of such regions recognized the key processes so affected concern the productivity of blood, muscle, and sperm. We begin to get a sense of what the early horse breeders were after.
To get some greater detail on the last cycle of equid expansion and contraction, Vera Warmuth at Cambridge examined the hairs plucked from the manes of over 300 non-breed horses from locations spanning Eurasia. The roots of those hairs provided retain an informative content from which patterns may be inferred. Rather than building them into a tree, and reflecting upon the branches, she developed a series of explicit models of how the demography of horses through time might have unfolded, and how domestication may have been impacted. Such model-building approaches are increasingly allowing us to explore more intricate scenarios in the human past. Here, Warmuth found maximum support for a ‘boom’ expansion of the horses from the eastern end of Eurasia some time after 200 thousand years ago, the ‘bust’ contraction very much later caught by human management over in the west, around Ukraine and North Kazakhstan.
The earlier work of Lister, Stanley, et al. had highlighted the high genetic diversity of domesticated horses, and how that might relate to multiple domestication and subsequent corralling and taming of wild animals. Warmuth’s study, drawing also on the potential of using Y-chromosome variation to separate male and female demographies, has refined and clarified that picture. The expansion from the east of Eurasia is caught by a domestication much further west (in the area of Ukraine and Kazakhastan corresponding to some of the early archaeological finds of horse management). This reasonably localized domestication is followed in many parts of Eurasia by systematic incorporation of local feral mares into the dispersed bands of horses; it would appear to have been active continued exploitation of the wild that has generated the genetic and physical diversity seen today. Even as we admire the refined physique of the thoroughbred horse, for many a pinnacle in human breeding and domestication, much of what we see is controlled by the genes of wild mares, roaming the unmanaged grasslands long after the ancestral domestic stallion was stalled.
The thoroughbreds themselves illustrate another development in ancient DNA studies. The horse provides an illustration of what evidence can come from molecules that are extremely old; it also demonstrates what is possible with DNA that is relatively young.
A range of institutions, from London’s Natural History Museum to the Animal Health Trust at Newmarket, curate relics of one of the most elite families of all, for lovers of the turf, easily competing with any of the royalties alluded to in Chapter Nine. Through such grand names as St. Frusquin and William the Third, the heritage of the elite family of thoroughbreds can be traced back to three ancestral stallions, Byerley Turk, Darley Arabian, and Godolphin Arabian, that impressed their owners with their grace and speed three centuries ago.
The sprinting potential of their living descendants, we can relate to aspects of genetic makeup, for example, the expression of a ‘speed gene’ that moderates early muscle growth to maximize quick sprints in early youth. At Camb
ridge, Mim Bower managed to acquire samples of a number of archived relics of this line, ranging from a metacarpus of the aforementioned William the Third, born in 1898, back to a humerus bone of the fabled horse Eclipse, born in 1764. The eleven thoroughbreds she analysed should surely reveal the history of this much desired gene. To her surprise, none of the eminent historical thoroughbred stallions held that gene.
Bower concluded that the gene may have arisen from a separate population, British mares with whom the thoroughbred stallions were mated, and as recently as the twentieth century. This chimes with what Warmuth discerned for an earlier episode in the horses’ history. The incorporation of local populations as mares proves to be an ongoing theme of how humans engaged with animals, conscious of lineage and protection of a line, but also active and flexible in crossing boundaries and bringing in genes and diversity from adjacent populations, be they wild, feral, or just the local variant. These animals no longer have a simple ‘before-and-after story’ taking them from wild to domesticated states. Evolution and co-evolution remain active in a constantly changing world, ever more coming into view through new molecular methods.
7
great journeys
leaving the cradle
The idea of great journeys blossomed in the nineteenth century and has dominated twentieth-century ideas about the human past. At one point, the idea of ‘progress’ existed in the European mind largely detached from the constraints of geography. Progress transcended place. Human communities around the world were simply at different points on a common journey of progress, a journey that could be described as unilinear evolution, a path of improvement along a single identifiable route. If communities had not yet turned to agriculture, then they soon would do, perhaps with a little colonial help. Towns, trade, monuments and the trappings of civilization would naturally follow. During the twentieth century, we have been more circumspect about the inevitability of progress, and more aware of variation, conflict and political upheaval in human history. Rather than envisaging the steps of progress as universal benchmarks, we see them instead more as historical episodes, transitions such as the beginnings of agriculture occurring at a particular place and time. Following those historical episodes are the journeys outwards from the point of origin, taking new ideas and new ways of sustaining life to far-flung regions, through contact, colonization or conflict.
Twentieth-century archaeology has continued to be absorbed in these journeys, not always the same journeys, but the underlying concept of movements and migrations, as ways of explaining changes in human culture and society. In a previous generation, there seemed nothing odd about that pioneer of archaeological fieldwork, General Augustus Pitt Rivers, charting the progress of humanity from excavations on his own Dorset estate. Why look further than your own backyard for a process unconstrained by geography? By the time the General was assembling his grandest typological schemes of linear evolution, however, the premise of inevitable progress was already coming to seem a little unrealistic, particularly among a younger and more cosmopolitan generation.
At the start of the twentieth century, at a moment when some quite astonishing discoveries about ancient Egypt were coming to light, a young Australian took the post of Professor of Anatomy at Cairo University. Grafton Elliott Smith decided to apply his scientific skills to the growing number of mummified bodies becoming known, while his fascination with the sophistication of their preserving methods and the wealth of their graves began to grow. In a land where wild barley sprang spontaneously from the Nile muds, he came to the view that the cemeteries of Egypt were the birthplace of the arts and crafts of civilization. He had the opportunity of returning to Australia in 1914, and of inspecting another group of mummified bodies from the Torres Straits Islands. What he saw convinced him of a link between the two groups. The methods of preservation used on these bodies from Australasia seemed to bear witness to the influence of the ancient Egyptian cultures on the far side of the world. In the following years, he traced patterns of similarity in a whole range of cultural features that pointed to contact. These included the practice of mummification, massive stone architecture, symbolic representation of the sun and the serpent, and the use of metals and domesticated plants and animals. Each of these features could be followed through the Old World and the New, and even to remote islands of the Pacific. The idea of a global diffusion of ideas was born, rooted in Egypt and reaching out to the ancient civilizations of the world.
Smith’s grand scheme never gained universal acceptance. The old guard saw their unilinear schemes of progress under threat, and a younger generation was keen on emphasizing the contrasts rather than the similarities between ancient cultures. However, Smith had paved the way for more modest schemes, ones that would succeed in providing alternative frameworks to unilinear evolution. One came from his fellow Australian, Vere Gordon Childe, whose contribution to the debate on agricultural origins was discussed in Chapter 5. At one stage Childe was quite interested by Smith’s hypothesis, but in due course his own encyclopaedic knowledge of world prehistory would enable him to come up with a more modest, but also more persuasive model. In this, he traced the spread of agriculturally based, urban civilization from the Near East across Europe. Within a more regionally compact framework such as this, the idea of diffusion of culture became the predominant archaeological model. In the middle years of the twentieth century, charting the pathways taken by those ancient migrants, or the ideas they passed on, became the prime quest of the prehistorian. Arrows proliferated across maps, linking artefact or monument types along a common path. Not everyone traced their paths in the same direction or within the same time scale. Before the widespread use of scientific dating methods in the 1960s there was a fair amount of leeway, both in what evidence was used to trace the path and in what date was ascribed to it. In Germany, Gustav Kossinna had provided what would become the prehistoric prelude to the Nazi version of history, surmising an Aryan rather than an Oriental source point for the arrows across his map, for the great civilizing journeys. Several alternative journeys were put forward to account for the commonality of particular language families, most notably the Indo-European language group that spanned a vast stretch of Europe and Asia. As we saw in the previous chapter, Maria Gimbutas drew together evidence from artefacts and weaponry, burial traditions and language elements to reconstruct three waves of expansion by horse-riding warriors between the fifth and the third millennia BC, carrying Indo-European language and transforming European culture on the way.
The decisive test for many of these great prehistoric journeys came when the dates of ancient monuments and prehistoric civilizations around the world no longer floated free, to slip effortlessly into one grand narrative or another. From the 1960s, a battery of independent scientific dates came into play and forced the world’s antiquities into authentic and verifiable time slots. Several of the arrows snapped in the process and had to be removed from the maps; the dates along their paths were all wrong. Armed with these new dates, the archaeologist Colin Renfrew took on the most established part of the story.
Europe as an archaeological study area has its pros and cons. Nowhere else has so much data been gathered about the human past. The stories we can build around this vast body of information are steeped in detail and complexity. However, they are also steeped in established views held by the continent’s unusually high density of senior academic figures, which may at times offer the young researcher a greater constraint than the data itself. What is more, Europe is the continent where the western notion of civilization was born, and people care about getting its myth of origins right. Not for the first or last time, redrafting the European story was no easy task. None the less, Renfrew’s critical use of both the growing body of carbon dates and the cultural evidence dispatched some of the best-known diffusionary arrows from the map. By the early 1970s, a new approach to the origins of European civilization was required.
To set this reconstruction in motion, Renfrew brought togethe
r a range of specialists at a conference on the explanation of culture change at Sheffield University. Among the speakers was the eminent geneticist, Luca Cavalli-Sforza. The new archaeologists of the 1970s had a great enthusiasm for predictive models from science, and Cavalli-Sforza offered one. It was a mathematical model that looked at the behaviour of a population undergoing sustained growth. Even without any conscious aim of migration, such an expanding population would in any case project a ‘wave of advance’, merely as a consequence of a large constellation of small journeys away from the over-populated core. He teamed up with the archaeologist Albert Ammerman to see if this worked with radiocarbon dates, and it did. The dates for the early farming sites also fell into a sequence of diminishing antiquity, moving outwards across Europe from the early agricultural sites in south-west Asia.
Once again, a wave of farmers was on the move, but this time on a schedule that matched up with the rapidly growing corpus of radiocarbon dates. Ammerman and Cavalli-Sforza concluded that, once domestication had occurred in the Fertile Crescent, the ecological advantage of farming then led to population growth. From this growth at the core, there emanated a wave of advance across the continent, tracked by carbon dates and genetics alike. According to this new working of the data, the diffusionists had focused on the wrong type of movement and too late a cultural episode to match the dates. It was not monument-building, metalworking, farming communities that actively carried the wave front forward. It was their distant ancestors, the very first pioneer farmers, responding to the pressures on the land they left.
