Tamed

by Alice Roberts

  It’s easy to leap to the conclusion that early farmers might have been deliberately selecting smaller, easier-to-handle, animals to breed from. While that may have been the case at the dawn of domestication, it seems unlikely that farmers would have continued to select smaller and smaller animals over the generations and millennia. So why were cattle continuing to shrink?

  The results from the careful osteological analysis – of bones from seventy sites across central Europe – allowed the archaeologists to test different ideas about what might have caused this reduction in body size. One possible explanation could be that domestic cattle were chronically underfed – but there are no signs of cattle being malnourished. A decrease in average size could come about as a side effect of a reduction in the degree of difference in size between male and female animals. Yet while there was a reduction in sexual dimorphism right at the start of the Neolithic, that trend didn’t continue as the cattle themselves got smaller. Cattle arrived in Europe some 3,000 years after that initial domestication; and, over subsequent millennia, the bones of European cattle showed a fairly consistent level of difference between males and females – and yet they continued to shrink.

  Climate change can also have an effect on the size of animals. Could this be the answer? Probably not, as you’d expect the wild cattle to be affected in the same way as the domestic ones – and they aren’t. Another possibility is that the apparent change in average size of cattle just reflects a changing ratio of female to male cattle. A larger proportion of adult females in a herd would fit with an increasing focus on milk production; in dairy herds, young males are often culled. This seems like a good hypothesis, then – but again it doesn’t fit the evidence. The bones of the Neolithic cattle didn’t show an increasing proportion of female animals. The scientists were doing a good job at rejecting hypotheses. After all that rejection, there was just one hypothesis left – and one which seemed to fit the evidence from the piles of bones perfectly.

  The ancient cattle bones from Neolithic central Europe revealed not only a decrease in size, but a rising number of juveniles – suggesting, this time, an increased focus on meat production. Young cattle grow quickly. By maturity, at three to four years of age, the rate of growth slows right down. You don’t gain much more meat by keeping a mature animal alive. So you cull more animals before, or just as, they reach maturity – and the proportion of juvenile bones in the middens around your settlements goes up. On its own, this still doesn’t explain the size reduction in cattle – because this is a phenomenon recorded in adult cattle; the juveniles are disregarded from the sample. But nonetheless, the high proportion of subadult bones is telling us something: in such a herd, many of the cows giving birth to calves will be immature themselves. These cows – able to reproduce but still with some growing to do – will tend to have calves with lower birth weights than their mature sisters in the herd. Smaller, lighter calves tend to grow up to be smaller, lighter cattle. It doesn’t mean that the European Neolithic herds weren’t being milked as well, but meat seems to have been a priority – and one which meant that European cattle were 33 per cent smaller at the end of the Neolithic than they’d been at the beginning. Later on, in the Bronze Age, the proportion of sites with subadults decreased – accompanied by a small increase in the size of cattle around this time. But this was a minor blip: on the whole, cattle continued to shrink right up until the Middle Ages, and it would be some time before they regained stature – and, even then, they were never quite as magnificent as their wild aurochs ancestors.

  Cattle also provided services other than milk and meat for our own ancient ancestors. Julius Caesar recorded the cultural importance of the wild aurochsen to the Iron Age people of Germany, and domestic cattle would continue to play significant roles in religious rituals and ceremonial fights. The cult of the bull in ancient Crete seems to have formed the inspiration for the myth of the minotaur. Cattle may have been drafted in as formidable, worthy opponents for heroes and matadors, but their size and strength was useful in a more prosaic way as well. They were the original tractors, used to pull ploughs and wagons. In many less industrialised parts of the world, they’re still used in this way. And sometimes, they’re better suited to the job than a mechanical alternative. It’s impossible to drive a tractor up to the high paddy fields of Longsheng in southern China – but an ox can get there easily, and pull the plough beautifully along the narrow terraces.

  The breeding and use of cattle for traction may explain another strange blip against that background trend of diminishing size of European cattle. During the Roman period, European cattle get a bit bigger – as shown by analyses of bones from sites in Italy, Switzerland, Iberia and Britain. Farmers may have been deliberately breeding and trading larger cattle, but the size increase could also reflect an injection of local, wild aurochsen genes. And perhaps larger cattle were particularly sought after at this time – as essential cow-power for the expanding wheat fields of the Empire. Nevertheless, cattle remained fairly small – much smaller than today – until well after the Middle Ages.

  On the hoof

  Following the initial diaspora of domesticated cattle, with the first farmers, throughout Europe, Asia and Africa, bovine populations continued to shift and blend, as people moved, taking their cattle with them. As civilisations blossomed and empires grew up, flourishing breeds of cattle were transported from their homelands to new pastures.

  The mitochondrial DNA of cattle in northern Italy suggests an intriguing link with Anatolia – which seems to date to much later than the original arrival of cattle in Italy. Herodotus wrote about the sufferings of people in Lydia – modern Anatolia – during an eighteen-year-long famine. Eventually, he tells us, a large contingent of Lydians left the shores of the eastern Mediterranean and voyaged to Italy. According to Herodotus, the settlers in Italy called themselves Tyrrhenians – and went on to found the Etruscan civilisation. It’s a rather romantic story, with seemingly very little in the way of other historical or archaeological evidence to back it up. But perhaps the cattle of northern Italy retain a faint genetic memory of an ancient migration from the eastern Mediterranean after all. Analysis of mitochondrial DNA from ancient Etruscan human bones has also been suggested to reflect a link between northern Italy and Turkey. It’s not a clear sign of a migration, though – it may just reflect how well these regions were linked by trade and mobility. But perhaps, just perhaps, Herodotus was right after all.

  Trade routes are also reflected in the genetic make-up of modern cattle. Zebu DNA in cattle in Madagascar undoubtedly reflects strong trading connections with India. But some significant movements of cattle, which show up in the genes, followed human migrations around the globe. A relatively recent introgression of zebu genes into African, taurine cattle probably reflects the Arabian expansion of the seventh and eighth centuries CE.

  After the Middle Ages, we start to see an increase in the size of cattle – which could either be due to selective breeding, or perhaps an indirect consequence of relative political stability and prosperity in Europe. After all, peacetime means that pitchforks can be used, not as weapons, but for their intended purpose of lifting hay.

  The bovine takeover of the Americas started at the tail-end of the fifteenth century. The first cattle to be loaded on to ships at Cadiz in 1493 – part of Columbus’s second expedition to the Americas – were headed for Santo Domingo, via the Canary Islands. Horses, mules, sheep, goats, pigs and dogs also made the trip. And they were soon joined by more – every fleet after that brought additional animals to add to the expanding herds and flocks.

  So there were no pre-Columbian cattle in the Americas – at least, that’s the traditional view. However, there’s a very real possibility that cattle may have arrived in North America some 500 years earlier, with the establishment of Viking settlements in ‘Vinland’ – probably Newfoundland. The Norse sagas specifically describe islands off Vinland where winter was mild enough for cattle to graze outside all year round. Still, th
ere’s no evidence that these Viking colonists left any descendants – human or bovine. The colonies were abandoned, and it would be centuries before Europeans ‘rediscovered’ the Americas. And despite the existence of at least one Viking Age settlement, at L’Anse aux Meadows, even the link between Newfoundland and the Vinland of the sagas is still questioned by some. On the other hand, there seems no reason to doubt the well-documented voyages of the Spanish and Portuguese. The Spanish transported cattle to the Caribbean; the Portuguese took cattle with them to Brazil – and these animals were the ancestors of Latin American Criollo or Creole cattle.

  During the eighteenth century, British pioneers led the way in systematic selective breeding – and specialised breeds started to emerge. Robert Bakewell bred the large, brown-and-white longhorn – principally draught animals, but also good milkers – while the Colling brothers produced the red or roan British shorthorn, good for meat and milk.

  Cattle breeders engineered crosses between particular breeds to bring out desired characteristics. The nineteenth century saw a period of bovine ‘anglomania’ where British shorthorn bulls were bred into continental European cattle. Productive breeds from Holland, Denmark and Germany were also exported to other European countries, and to Russia, to improve domestic herds. Hardy Ayrshire cattle from Scotland were bred into Scandinavian populations. There was a mass introduction of zebu cattle into Brazil in the nineteenth century, to improve the existing herds there. Most of the milk produced in Brazil today comes from Girolando cattle – an indicine-taurine cross. In fact, the founding populations seem to have been part-zebu already – reflecting those already complex connections between south Asia, Arabia, North Africa and Europe. And cattle have done well – extraordinarily well – in their new, New World habitats. In Brazil – home to cattle for less than 500 years – there are now more cattle than humans. Some 200 million people live in Brazil – and some 213 million cattle.

  In the second half of the twentieth century, cattle breeding got even more technical, with the introduction of artificial insemination. Some cattle were carefully bred for maximum milk production – such as Holstein-Friesians, now the most populous cattle breed in the world. Others were – literally – beefed up, with traits for heavy musculature promoted through selective breeding. Some cattle were also bred to suit particular environments, from lush green grassland to virtual desert. But it wasn’t all about productivity: aesthetic characteristics were under selection as well. An astonishing variety of cattle emerged – not quite as astonishing as the diversity within dogs, but prodigious nonetheless. From white to red to black and everything in between, short-haired to frankly shaggy, small and large, long-horned, short-horned and hornless – the variation in appearance of modern cattle is nothing short of impressive. Selection has changed over time – we now prefer cows which produce less fatty milk, and black-coated beef cattle are currently fashionable in the US. In the developed world, cattle are no longer needed as draught animals, so selection for strength and stamina, pulling the plough, has receded into history.

  But selective breeding over the last 200 years – in cattle as in dogs – has created a paradox: there may be plenty of variation, phenotypic and genotypic, between breeds; within breeds, it’s a different story. This narrowing down of variation has been carried out quite deliberately. For most of their history, domestic cattle were subject to ‘soft selection’ as farmers encouraged reproduction amongst animals that were more productive, or better suited to particular environments. And there was plenty of gene flow between emerging breeds. But over the last two centuries, breeders have focused on reducing the variation within breeds – until even coat colour became consistent. With the tight control over reproduction facilitated by artificial insemination in developed countries, the possibility of interbreeding between cattle breeds was practically eliminated. The result of this restriction on breeding, together with strong selection, is a species which actually consists of lots of separate, fragmented populations. Each one is at risk of all the problems inherent in inbreeding, including higher rates of genetic disease and infertility, and population-wide susceptibility to infectious disease. In the wild, fragmented populations with little genetic variation are the ones which are most at risk of extinction. And yet tightly constrained, industrial breeds may be – in the here and now – more productive than traditional breeds. For farmers, switching from a traditional breed to an industrial breed can be an economic no-brainer. But in the long term, it’s not sustainable. Once a domestic breed has gone extinct, all the ‘genetic resources’ it contained are also lost. Geneticists are worried about the future of cattle – and our own food security – if the fragmentation of populations and inbreeding continues. They’re worried about domestic sheep and goats too, but the situation for these animals differs from cattle as there are several species of each, and wild species still exist as well. Although cattle can hybridise with other, extant bovine species – which might be useful genetic resources in the future – the wild ancestor of cattle went extinct centuries ago.

  Resurrecting the aurochs

  As the global population of domestic cattle burgeoned, the numbers of wild aurochsen dwindled and dwindled. Once they had roamed right across Europe, into central and southern Asia, and North Africa. But by the thirteenth century CE, the territory of the wild aurochs had contracted until they only existed in central Europe. Aurochsen survived longest in Poland, where they were protected by royal decree, and even fed during the winter, to ensure the sport of kings. But even royalty couldn’t save them in the end. Domestic cattle encroached on the habitat of the aurochsen. Cattle diseases and illegal hunting also played a role. But eventually, their demise was ensured by a lack of interest. In 1627, in the Jaktorów game preserve in Poland, the last recorded aurochs, a female, died.

  The loss of these large grazers – especially as it happened relatively recently – is lamentable. There are very few species of ‘megafauna’ left in the world, and a large portion of the blame for their disappearance rests with us humans. In a more selfish way, losing these species also means that we’ve lost them as genetic resources. We can’t inject new hybrid vigour into our cattle populations by interbreeding them with aurochsen. And there are also wider, ecological reasons to regret the absence of these animals in our modern landscapes. Without large grazers, wild places become uniformly forested. Nature becomes less diverse.

  And this is why some cattle breeders are attempting to bring the aurochs back to life – at least, they’re trying to create a new breed which will be as aurochs-like as it could possibly be. The breeders of the Tauros Foundation in the Netherlands have chosen several European breeds which seem to retain some ‘primitive’, aurochs-like characteristics – in size and shape, length of horns and grazing behaviour. By breeding these various types of modern cattle together, they are hoping to resurrect the phenotype – the appearance and possibly the behaviour too – of the aurochs. However, recent advances in molecular genetics could mean that it may be possible to do more than breed something which looks like an aurochs on the surface. It may be possible to produce an animal which is, through and through – genetically – an aurochs.

  The first step towards doing that is to characterise an aurochs’s genome – not just its mitochondrial DNA, or its Y chromosome, but its entire, nuclear genome. In 2015, a team of researchers did just that, sequencing the genome of a 6,750-year-old British aurochs. Taking a sample of bone powder from a humerus found in a cave in Derbyshire, they were able to extract the DNA and read the code. This animal lived a thousand years before the first domestic cattle reached Britain: it was pure, unadulterated aurochs. And when the geneticists compared this aurochs’s genome with that of modern, domestic cattle, they found clear evidence of later interbreeding between aurochs and domestic cattle. A range of British breeds, including Highland, Dexter and Welsh Black, contained DNA from the ancient, British aurochs population. There was no evidence of interbreeding with this British aurochs in non-British b
reeds – which is important as it suggests the interbreeding really did happen in Britain, between the local domestic cattle and their wild cousins, rather than happening earlier, in mainland Europe. It adds to the evidence of interbreeding from those mitochondrial DNA and Y chromosome studies – so in a way, the ancient aurochs are still with us. Just how much aurochs DNA could there be, knocking around in the genomes of living cattle, from such ancient liaisons? If more aurochs genomes are sequenced, it should be possible to find more breeds which have these recent genetic additions from aurochs. This could be a better way of finding cattle to breed from, to ‘recreate’ an aurochs, than simply looking at characteristics. But both approaches beg the question – what’s the real point of attempting this ‘de-extinction’? Is it to breed a creature which looks like the extinct animal? Is it to create an animal which is, genetically, as close as possible to the original, lost species? Or is it to produce a new breed which could fulfil similar roles in an ecosystem to those performed by the extinct animals? What is most important in this endeavour – looks, genetics or behaviour? While there’s a bit of me that would love the chance to see a real, living aurochs, the opportunity to reintroduce a missing keystone species into a wild ecosystem is a more worthy cause, and a more valid reason for attempting de-extinction.