Genetics and the peopling of Britain: We are all hybrids

Recent advances in the science of human origins refute racist ideology, writes STEVE DRURY in this guest post

We are in the midst of a resurgence of racism, white supremacism and all the other trappings of right-wing populism, together with growing physical threats from some who adhere to those ideologies. This trend depends on a morass of origin myths, pseudoscience, denialism and conspiracy theory – an “intellectual” foundation that actually permeates more widely than merely in overtly far-right fringe groups. Sadly, it is part of the cultural baggage of a majority.

Yet rapid advances in the science of human origins have been providing powerful refutations of all kinds of nonsense and mindless prejudice.

Britain has long been a relatively quiet repository of day-to-day, casual racism and ideas of supremacy that stem from its former possession of colonies, together with the idea of an

Footprints made by the earliest visitors to Britain 850,000 years ago (Picture: Simon Parfitt, British Museum)

island fortress against all comers, benign or malevolent. So how the “British” and their early culture came into existence is an excellent starting point for countering the insidious backwardness of this politics.

Earliest visitors

Evidence for the presence of humans in Britain goes back about a million years. For most of that time, however, any occupation was probably temporary. Stone tools are the most durable signs that early humans paid the British landscape a visit, fossil remains being rare and generally just a few fragments.

The earliest known traces occur in ancient river deposits exposed by wave erosion on the Norfolk coastline. Pear-shaped, double-edged stone tools, known as “bifacial axes” (archaeologists are uncertain about how they may have been used) turn up there from time to time. But the most dramatic sign of human visitors became exposed briefly in 2013 in the form of footprints, identical to our own, in 850,000-year-old river silts at Happisburgh (pronounced “Hazeborough”) in Norfolk.

Several individuals with differently sized feet clearly milled around for a while, and they probably carried and misplaced the stone tools found nearby. Who they were can only be worked out from skeletal remains, of which they are none of that age anywhere in Britain. They may have been members of the species Homo antecessor, whose remains from about the same time in the past have been found in northern Spain. Scientists at the Natural History Museum have found traces of at least nine separate waves of occupation of Britain by early humans in the millennia following the first known visit.

Over the last two and a half million years, Britain’s history has been dominated by periodic and dramatic changes in climate that would have impacted early populations severely. Over the last million years there have been nine ice ages, during each of which Northern Europe, including Britain, would have been uninhabitable because of vast ice sheets and bare, frigid polar deserts devoid of vegetation beyond the glacier fringes.

Roughly every 100,000 years climate warmed to reach “interglacial” conditions similar to those that prevail today. Interglacial episodes opened windows of opportunity, ten to twenty thousand years long, for human hunter-gatherer bands to move back into Northern Europe as vegetation spread to be followed by potential prey animals.

Until about 160,000 years b.p. (before the present) a land “bridge” formed a permanent connection between Britain and the rest of Europe, the highest part being a Chalk ridge across what is now the Straits of Dover. Whenever huge land glaciers formed during ice ages, sea level fell by as much as 130 metres, to expose wider tracts of low-lying land in what is now the North Sea, over which ice sheets spread southwards.

Each time conditions warmed, the Chalk ridge dammed water from melting ice sheets, for the resulting lake eventually to spill over the dam. This caused massive floods into what is now the English Channel. These events are recorded by a network of deep valleys on the floor of the present Channel.

Gradually, such repeated overspills eroded away the permanent connection with Europe. Mega-floods finally broke through the Chalk ridge about 160,000 years b.p.. Yet a low-lying land bridge emerged each time land ice increased and sea level fell, the last one being present until quite recently in a geological sense. With the retreat of the vast ice sheets and the onset of warmer conditions, sea level rose so that Britain became an island. The most recent isolation from Europe began about 9000 years ago.

While a permanent land bridge existed, hunter-gatherers could freely move back and forth as permitted by climatic conditions and the availability of game and plant life. At least twice,

A reconstruction of catastrophic erosion of the Chalk ridge that once joined Britain to Europe by glacial meltwater formed during a warm interglacial period (Picture: Chase Stone/Imperial College London)

around 700,000 and 500,000 years b.p., another human species, Homo heidelbergensis, took advantage of warmer periods to colonise Britain – only to retreat as climate deteriorated. There is also evidence that Neanderthals moved back and forth several times after 400,000 years ago.

The last time that they returned to occupy parts of Britain was around 50,000 years back, as sea-level fell during the onset of the last Ice Age to expose the temporary land bridge. They haven’t been back since, because they totally vanished as a separate group around 40,000 to 30,000 years ago, but see a little later. …

For around 300,000 years the sole human occupants of Europe, come ice age or interglacial, were Neanderthals. Their range extended through Central Asia as far east as Tadjikistan and Siberia, and into the Middle East. Aspects of their physiology suggest that they were cold-adapted, heavily muscled and capable of taking on the largest of prey animals – for instance woolly mammoths.

Until a mere eight years ago, anthropologists regarded Neanderthals as a separate species from us. In 2010 a complete copy of Neanderthal DNA was extracted from fossils found in Croatia. Comparing it with the genome of living people yielded an astonishing anthropological conclusion: most people now living in Europe and Asia contain up to 5% of Neanderthal DNA. There is only one possible conclusion: that anatomically modern humans, both male and female, repeatedly interbred with Neanderthals. That probably happened quite regularly, otherwise the sign of such liaisons in our DNA would have been diluted to vanishing point after the Neanderthals became extinct, around 30,000 years b.p.

Caves in the Middle East have yielded remains of both modern humans and Neanderthals who co-occupied a relatively small area from about 130,000 to 80,000 years b.p., a period when fully modern humans began migrating from their origins in Africa. So the first hybrid offspring probably date to that time, although there is no reason why other fertile encounters might not have occurred later, as modern humans moved into the area of Neanderthal occupancy in Europe.

As you will read later, Britain was the destination of three major waves of modern human immigration and colonisation from the late Stone Age to the Bronze Age, the last bringing the DNA and the root language of ancestors of most modern Europeans from the Atlantic to the Russian steppes, and from the Mediterranean to the Arctic.

Nearly all people who settled Britain in these waves and in lesser ones since the Roman Conquest carried some Neanderthal ancestry. Being partly Neanderthal brought benefits that show up in modern human genes: up to half of our immune resistance to Eurasian pathogens; enhanced blood coagulation and healing, assisting recovery from wounds and haemorrhage when giving birth; aspects of our energy metabolism; more insulating skin; improved night vision, etc. But there have been drawbacks; tendencies to depression, bipolar disorder and addiction; increased risk of Type 2 diabetes, Crohn’s disease; and some autoimmune conditions.

The first remains in Britain of fully modern humans and their tools are from caves in Devon and South Wales, dated at between 40,000 to 30,000 years b.p.. The fall in sea level while ice caps began to accumulate in the Northern Hemisphere exposed the bed of the southern North Sea and an easy route from continental Europe to Britain. It was an area of low-lying swamps and estuaries, that has been called Doggerland after the shallow-water Dogger Bank in the southern part of the present North Sea.

By 20,000 years b.p., during the last glacial maximum, an advancing ice sheet up to 2 kilometres thick buried Scandinavia, Northern Europe and most of Britain and Ireland. The populations that had become established at these high latitudes migrated far to the south. At about 15,000 years b.p. rapid warming began, taking Northern European land temperatures almost to the levels that prevail today.

Since ice caps melt slowly, sea level remained low enough for Doggerland still to be crossed on foot. Modern humans took advantage, some occupying caves at Creswell Crags in Derbyshire to hunt horses grazing on what would then have been open steppe – trees did not re-colonise Britain until about 9000 years ago. Their occupation was short-lived because temperatures once more plunged to ice-age levels around 12,900 years b.p. That catastrophe happened within just a few years and mountain glaciers advanced again.

What became of the pioneers of Creswell is not known: they either perished or managed to travel back to southern Europe. Britain was again deserted. Conditions remained glacially frigid for more than a millennium until, equally abruptly, they improved to roughly present levels 11,700 years b.p., with Doggerland still exposed as a route back to Britain.

The earliest permanent residents

For humans to make the journey back to Britain depended entirely on vegetation becoming re-established on barren land left by the frigid period. Human bands may have followed grazing animals onto Doggerland, probably in seasonal migration cycles. Trawlers continue to dredge up animal bones and human tools from the shallowest parts of the southern North Sea that were land until about 8500 years b.p., when ice caps completely melted from Europe.

Detecting the ephemeral presence of fully nomadic hunter-gatherers returning to Britain is not easy. Signs of constructions are rare and often the only signs of human habitation are scatters of flint chips where they made or retouched stone tools. Detailed study of Star Carr, one such site in North Yorkshire, revealed traces of a former lakeside settlement with thatched roundhouses and timber platforms, with an extent of more than 2 hectares. Charred material, such as hazelnut shells, provide a maximum radiocarbon date of a little less than 11,000 years ago and a period of occupation or around 900 years.

The culture of these settled hunter-gatherers, which preceded the first evidence for farming in Britain, is known as the Middle Stone Age or Mesolithic. The evidence of how they lived includes a wide variety of stone, bone and wooden tools; evidence of skilled carpentry such as planking; ornaments made of shale, amber, “fool’s gold” and iron ore, some with abstract decoration; and ritual headdresses or masks made from red deer skulls. Discarded animal bones reveal a wide range of food species. The fact that the red deer skulls have antlers attached indicates occupation from October to April when stags carry antlers, whereas bones of summer migrant birds suggest at least some periods of year-round habitation.

Modern humans have populated Britain continuously since the Mesolithic. But who were these first inhabitants? Where were they from? Star Carr has revealed no human fossil remains, but slightly younger cave sites in South Wales, Devon, West Scotland and Somerset have.

In 2017, the DNA in six Mesolithic human bones from Britain was sequenced, to reveal astonishing features. That extracted from the well-publicised Cheddar Man’s skull contained clear genetic evidence for brown, perhaps black hair, blue-green eyes and dark to black skin pigmentation. He shared ancestry with other European hunter-gatherers from Luxembourg, Spain and Hungary, all of whom probably hailed from the Middle East.

Comparison with DNA from living, pale-skinned British people shows that these modern Britons share 10% of their genetic make-up with Cheddar Man and other dark-skinned Mesolithic people from the rest of Europe. An early Neolithic (about 5500 years old) man from Derbyshire was also dark skinned.

The usual explanation of dark versus light skin colouration is that melanin, the dark pigment responsible for the former, evolved in Africa and was retained by migrants into other low-latitude regions as a protection against damage by the ultra-violet radiation in sunlight. Yet

Reconstruction of the head of Cheddar Man, based on his skull and DNA (Picture: Kennis & Kennis Reconstructions; photo Tom Barnes/Channel 4)

UV is an important factor in the skin’s production of vitamin D, deficiency in which causes rickets, among other conditions. It has been widely supposed that migration of dark-skinned people to higher latitudes led to their lower production of vitamin D. This is based in part on the greater proclivity of African Americans and Afro-Caribbean people, with slave ancestry, to vitamin D deficiency. In the case of the original migrants out of Africa, who first left that continent about 130,000 years ago, the populations that reached mid- and high latitudes were subject to natural selection for lighter pigmentation to increase vitamin D productivity: hence the pale skinned people of Europe and central Asia.

The newly discovered dark pigmentation of Mesolithic and some early Neolithic Europeans, renders that popular view suspect. A high-protein diet that includes nuts, mushrooms, fish and terrestrial animals’ liver supplies adequate levels of vitamin D, thus requiring no adaptation of skin colour to high latitudes. In fact Native Americans together with Inuit and other people living north of the Arctic Circle retain dark skin pigmentation, being hunter-gatherers or having only abandoned that life style in the last few hundred years.

Adopting a diet dominated by cereal crops, which have low vitamin D contents, after the rise of an agricultural lifestyle during the Neolithic between 10,000 and 5,000 years b.p. and subsequently would, however, have created a strong selection pressure for pale skin able to build up vitamin D.

The assumption that Britons and other Europeans “have always been white” is simply a racist myth. That condition is most likely to be a reaction to a radically changed, inadequate diet.

The first farmers in Britain

The most important human cultural shifts following the last Ice Age came with the development of agriculture and domestication of herd animals, first in the “Fertile Crescent” of the Near East around 10,000 years b.p., then successively on all the habitable continents, except Australia.

The earliest sign of the so-called “Neolithic Revolution” in Britain was sudden deforestation that began about 7000 b.p.. The production of storable grain crops and herds restricted by domestication demanded permanent settlements, with early British examples dated at around 5500 b.p.. Ritual architecture on a sometimes monumental scale began to appear in the British islands soon after, the earliest example (5200 b.p.) in north-west Europe being Newgrange in County Meath, Ireland.

Both agriculture and its accompanying early ritual practices emerged quite late in Britain compared with further east in continental Europe. There is a rough trend of decreasing age from east to west for the adoption of agricultural practices across Europe, which begs the question: Was it spread by migrating farmers and herders, or did the culture itself spread? Opinion among archaeologists has swung one way or the other, with meagre, tangible evidence, since 1923, when the Marxist archaeologist V. Gordon Childe proposed the Neolithic Revolution theory. The advent of DNA sequencing of samples from both living people and ancient human bones has transformed the debate, and swung it decisively towards a conclusion.

Did agriculture spread through Europe, to Britain, by means of migration, or cultural diffusion? A 2017 genetic study was principally about resolving this dilemma. It also provided dramatic evidence about the early hunter-gatherers who spread north and west as the ice retreated.The authors added to a rapidly growing DNA data base for European Neolithic people, including genomes for 67 Neolithic skeletons found in Britain. These new data, and the wider database, give overwhelming support to the conclusion that agriculture was introduced by continental farmers steadily moving across Europe.

The DNA of these migrants did not wipe out the genetic make-up of their predecessors in Britain, but diluted it considerably to about 30% of the British Neolithic genome.

The data suggest that the hunter-gatherer and farming groups maintained cultural and genetic boundaries for several centuries after initial contact. Because a hunter-gatherer lifestyle can support only low population densities, the Mesolithic population could simply have been outnumbered by incoming farmers and herders when it came to interbreeding.

Interestingly, neither British Mesolithic nor early Neolithic individuals carried the lactase persistence genes responsible for tolerance in adults of the lactose sugar in milk and dairy products that most living Europeans carry: the early farmers ate their livestock rather than milking them. Analysing the early British farmers’ genetic make-up shows that the immigrants were substantially descended from Neolithic populations in the Iberian Peninsula and ultimately from people originating in Anatolia (Asian Turkey), part of the Fertile Crescent. The wider European DNA data from the remains of several hundred individual Neolithic farmers suggests a two-pronged westward migration from Anatolia over a period of several millennia, one along the Danube from the shores of the Black Sea, the other along the Mediterranean coast.

Neolithic Britain experienced a cultural explosion that stemmed from the development and spread of agriculture, elements of the culture having possibly been brought with the farmers from elsewhere in Europe and Asia. Its most famous manifestation is Stonehenge and the surrounding “ritual landscape” of Salisbury Plain, the largest complex of its kind in Europe. It is now believed to have represented symbolically the living and the dead, to which Neolithic people travelled from all parts of Britain at particular seasons. They brought livestock for massive feasts and cremated remains of their deceased relatives to be spread in the “land of the dead” around the Stonehenge monument.

The culture of henges and stone circles in Britain extended as far as Brodgar on Orkney. The Stonehenge and Brodgar complexes are thought to have been initiated around 5000 years b.p., undergoing repeated changes through the following 600 years. Around 4400 years b.p., the ritual complex at Brodgar was ceremonially destroyed, the demolition being accompanied by an enormous feast involving several hundred cattle.

At roughly the same time the Salisbury Plain complex records the burial of a unique, high-status individual – the “Amesbury Archer” – with totally novel grave goods: the first metal artefacts recorded in Britain (three copper knives); metalworking tools; sophisticated accoutrements of archery, and pottery in the “Beaker” style, previously absent from the British archaeological record.

Nearby graves of around the same age also contained archers and “Beaker” pottery. The “Amesbury Archer” himself was unique in another respect: chemical analysis of his teeth revealed that he originated in the European Alps rather than Britain. Coinciding with the archer burials, the structure of Stonehenge itself was changed, and presumably the ritual practices too. This marks the beginning of the brief Copper Age in Britain and is supported by circumstantial evidence for the use of copper axes in construction of part of the nearby Durrington Walls complex. This henge was used for only a brief period towards the close of the Neolithic, and again hosted monumental feasts.

The horse culture from the steppes

The late Neolithic in the rest of Europe records the appearance of the Beaker pottery at a host of sites. It seems to have spread rapidly westward from eastern Europe between 4750 to 4500 b.p. and within a century had spread to Britain.

Beaker artefacts are often associated with evidence for early copper- and then bronze metalworking. Since many of the sites contain human remains and are well-dated, the previously mysterious Beaker culture and the Neolithic to Bronze Age transition became an irresistible target for human DNA analysis once the method became cheap and rapid: again, was it a spread of ideas or the movement of people?

As with the Neolithic agricultural revolution, this approach has recently yielded dramatic results. At around 4400 b.p., the genomes of ancient British individuals abruptly changed, so that the dominant genetic “signature” of Neolithic people collapses to a level in the

Examples of the Bell Beaker culture from southern Germany (Photo: Thomas Ihle/ Creative Commons)

population that, except for two instances, does not rise above a 25% contribution. Clearly, the Beaker culture was brought by a sudden, very large influx of genetically different people. These migrants introduced the genes responsible for reduced skin and eye pigmentation that remain dominant to the present. Yet they too do not show the lactase persistence gene needed for tolerance of dairy products in adults, which suggests that dairy farming arose in Britain later than 3500 years b.p..

The “Beaker” genetic signature is closely related to DNA from early Bronze Age herders of the Pontic Steppe in south-east Ukraine and southern Russia: the Yamnaya people. In turn, the Yamnaya descended from a mixture of earlier hunter-gatherers from the Lake Baikal area of Siberia and others from the Caucasus and Iran. Remarkably, data from the Siberian hunter-gatherers form a genetic link between later people from both Europe and the Americas, which suggests that descendants of the early Siberians migrated both westwards, eventually to Europe, and eastwards to cross the Bering Straits to the Americas.

The Yamnaya were the earliest humans to domesticate horses for riding and pulling wheeled vehicles. They could therefore migrate rapidly. An interesting feature of the DNA carried by males now living in northern and eastern Europe is the high proportion that possess Y-chromosome DNA (passed only from father to sons) with clear links to that of Bronze Age Yamnaya. All kinds of connotations can be placed on this, the simplest being that the migrant groups were dominated by male Yamnaya who subsequently produced children with women of earlier European peoples. The mitochondrial DNA (passed only from mother to daughters) of living European women shows little sign of an explosive influence of an influx of Yamnaya females.

There is also a distinct possibility, from Yamnaya links with DNA samples from living people in the Indian sub-continent that the Yamnaya introduced the mysterious proto-Indo European language from which the bulk of modern European languages are thought to have evolved.

By the Iron Age, which began in Europe sometime between 2800 and 2600 years b.p., historic sources suggest that Indo-European languages dominated all of Europe except for a few areas where pre-Indo-European languages, such as Hungarian, Finnish, Estonian, Sámi (Lappish) and Basque, are still spoken.

Later immigrants from Europe – including those arriving with the Roman Conquest – had very similar genetic ancestry to the Iron Age population of Britain; i.e. a complex, hybrid mixture.

Examining the genetic variation among every group of living humans on every continent leads to a clear conclusion: yes, there are differences, as there are in language, but overall 99.9% of the DNA of all human beings living today is the same, largely due to mixing and interbreeding. There are no “races” – as this great video shows. 26 April 2019.

■ Earlier discussion articles on human origins by Steve Drury, Chris Knight (with a response here) and Mike Nelson

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