Britain E-Book

Alistair Moffat

• Herausgeber: Birlinn
• Kategorie: Geisteswissenschaft
• Sprache: Englisch
• Veröffentlichungsjahr: 2013

Seitenzahl: 551

Beschreibung

 Based on exciting new research involving the largest sampling of DNA ever made in Britain, Alistair Moffat, author of the bestselling  The Scots: A Genetic Journey , shows how all of us who live on these islands are immigrants. The last ice age erased any trace of more ancient inhabitants, and the ancestors of everyone who now lives in Britain came here after the glaciers retreated and the land greened once more. In an epic narrative, sometimes moving, sometimes astonishing, always revealing, Moffat writes an entirely new history of Britain. Instead of the usual parade of the usual suspects – kings, queens, saints, warriors and the notorious – this is a people's history, a narrative made from stories only DNA can tell which offers insights into who we are and where we come from. 

Leseprobe

The British

A GENETIC JOURNEY

This eBook edition published in 2013 by Birlinn Limited West Newington House Newington Road Edinburgh EH9 1QSwww.birlinn.co.uk

Copyright © Alistair Moffat 2013

The moral right of Alistair Moffat to be identified as the author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988

All rights reserved. No part of this publication may be reproduced, stored or transmitted in any form without the express written permission of the publisher.

ISBN: 978-1-78027-075-3 eBook ISBN: 978-0-85790-567-3

British Library Cataloguing-in-Publication Data

Contents

List of Illustrations

Maps

Preface

Part 1

1 Origins

2 Beyond Eden

3 Britain Begins

4 Day In, Day Out

5 The Coming of the Kings

6 On the Edge of Beyond

Part 2

7 The Wanderers

8 The Sons of Death

9 The Royal British

10 Comings and Goings

Bibliography

Index

List of Illustrations

James D. Watson and Francis Crick with their model of the DNA molecule

Maurice Wilkins

Rosalind Franklin

Francis Crick’s original sketch of the double helix

The Great Rift Valley of Tanzania

The Olduvai Gorge in Tanzania

Louis Leakey measures the fossil-bearing strata in the Olduvai Gorge

Richard Leakey

Excavations in the Denisova Cave

What Neanderthal men looked like

The famous 15th-century map showing Vinland

Horses, cattle and rhinoceros depicted at Chauvet Cave

What Cheddar Man may have looked like

The Ring of Brodgar, the Ness of Brodgar, the Stones of Stenness and Barnhouse

The Stones of Stenness

Stonehenge

The Amesbury Archer and his grave goods

Jacob Grimm

Eildon Hill North, showing the hut circles near the summit

A reconstruction of part of Hadrian’s Wall

William the Bastard as he stepped ashore to become the Conqueror

Grubbing for edible potatoes in the Irish Famine

The Venerable Bede

Mousa Broch, Shetland

Maiden Castle in Dorset

Boudicca foments bloody rebellion

Offa’s Dyke

Jewish immigrants arriving in early 20th-century London

Enoch Powell

Examining a DNA sequence

Preface

WHEN HERODOTUS of Halicarnassus wrote history in the fifth century BC, he intended it to be something like an investigation, the collation of statements about events, people and circumstances made by those who had been there and seen them. Like a detective, he was pursuing enquiries. In Greek, ‘history’ meant something like ‘testimony’. Soldiers who fought in battles, travellers who had seen Nile crocodiles, supplicants who had bowed before Persian kings – they were the sorts of people Herodotus wanted to hear from. But as timelines lengthened and perspectives shifted, historians inevitably came to depend on more distant sources, usually the written records of what witnesses or the actors in important episodes said about them. And for many centuries, most of the writing in Britain was done by clerics who were chroniclers often far removed from the action, rarely actual witnesses. Into the modern period archaeology came to supplement the patchy survival of documentary records, and for the long millennia before Herodotus and the statements of witnesses, what could be excavated and reconstructed became virtually the only source of reliable information. Without the patience, skill and imagination of generations of archaeologists, our prehistory would amount to little more than a set of assumptions and guesses.

Recently, population genetics and in particular the study of ancestral DNA have added an entirely new dimension to our understanding of our past. The ability of scientists to identify the origins and dates of DNA markers and to use them to track the movement of people across the Earth has been revealing, sometimes startling. The dim and very distant prehistoric past can come brilliantly and movingly alive when the passage of a marker is traced from Manchuria and the shores of the Yellow Sea in the North Pacific clear across the Eurasian landmass to be found in Edinburgh in 2013.

For many millennia the last ice age held Britain and much of the northern hemisphere in its sterile, savage grip. In the brilliant white landscape of the ice-domes, frozen mountains a kilometre thick where incessant hurricanes whipped around their flanks, nothing and no one could survive. That brute fact made Britain a clean slate, a place waiting for its people and their DNA to come. When temperatures at last began to rise, the glaciers rumbled, groaned, splintered and cracked, and the land greened once more, people returned. These pioneers, the first of our species to see the rivers, the grasslands, the forest canopy and the hills and mountains that had been sleeping under the ice-sheets, are amongst our earliest ancestors. They may seem like another race, but DNA confirms an unbroken link. And when the last of the ice had gone, more people came north to hunt and gather in the wildwood, to fish and forage on the seashore, and to begin Britain.

Over thousands of years of prehistory, our ancestors walked to the farthest north-west of the Eurasian continent. DNA maps their movement and can approximately date their arrival. For at least four millennia after the ice, Britain was a peninsula and our people could make their journeys dry-shod. The landscape they entered was virgin. The ice had swept all life out of Britain and after c 9000 BC the land waited for the hesitant tread of the earliest pioneers. That simple fact makes our islands the sum of many migrations, a destination at the farthest north-west reach of Europe for many genetic journeys. A nation of immigrants on the edge of beyond.

All human beings, indeed all living organisms, have DNA, and that means something unarguable: we are all part of history. When Herodotus’ witnesses reported, they tended to remember the doings of the great or the mighty, kings, queens, warriors, battles and politics. But DNA makes us all witnesses, everyone who lives in Britain. Neither spectators nor the crowd barely discernible in the dimly lit background, we are – every one of us – actors in the unfolding drama of our history.

The Irish Sea Glacier

One of the most striking images in studies of the last ice age is what some scientists believe should be called the Irish Sea Glacier. They believe that it rumbled for 700 kilometres from its source in the ice caps of Scotland and Ireland and then squeezed between higher glaciated land either side of the North Channel. It pressed on the northern coasts of Cornwall and the Scilly Isles. It is even conjectured that the glacier continued to flow south even when parts of south Wales, the Bristol Channel and the coasts of south-west England were ice-free. It was a kind of ‘valley-glacier’ of the sort seen in the Himalayas. Others disagree that such a glacier ever existed, but the value of such speculation is that it forces us to visualise how different familiar landscapes and coastlines were in the deep past.

‘The past is a foreign country, they do things differently there’, was the opening sentence of L.P. Hartley’s The Go-Between, and it is apposite in considering the mysteries of our prehistory. Human sacrifice, cannibalism and the decapitation of children are all abhorrent practices now, but they were part of the experience of our direct ancestors, people whose DNA many of us carry. Fragments of their lives, like the unmade pieces of an archaeological jigsaw, lie around us on every side and as we try to make a clearer picture of the ranges and camps of hunter-gatherers, the great timber halls of the early farmers and the rituals that took place inside the stone circles, we must never fall into the trap of thinking of our ancestors as foreign. As Hartley wrote, the past is foreign, but its people were our people and their story is seamless, part of our story.

The balance of this book is heavily skewed to our prehistory for the excellent reason that the nine millennia before written record form the overwhelming proportion of our history. The early immigrations occurred before the brief visit of the Romans in the first century BC, and it is in tracing these that DNA studies can be most illuminating. But there is also a good deal to say about the first millennium AD. DNA can shine a light on what used to be known as the Dark Ages, the time of the Anglo-Saxons, the Vikings and other Northmen. After 1066, the picture stabilises as significantly fewer new people came and settled.

Since the industrial and agrarian revolutions, and the beginning of affordable sea and rail travel, Britain has seemed to become restless once more as many people moved. Across the Atlantic and further, from countryside to town and city and from upland to lowland, it appears that our people have left their native places in large numbers. But these changes seem more apparent than real. When those who have their ancestral DNA analysed are asked to name and locate their grandparents, it turns out that the demographics of Britain have shifted less than we think. When a Pictish marker was identified in 2013, many of those who carried it still lived in the ancient territories of Pictland in central and north-eastern Scotland.

More recently, Britain has seen an obvious influx of immigrants. After the Second World War, significant numbers of black and brown people have come mainly from the Caribbean and southern Asia to settle. They have not always been welcome and occasional outbursts talk of a threat to the British way of life. Not only is this shameful, it is inaccurate. At the outset of the twelfth millennium after the ice, Britain continues to be the destination of immigrants, just as it has been throughout all that long time. Incomers are not a threat to the British way of life, they are the British way of life. Our islands have been constantly enriched and renewed by the arrival of immigrants, they and their DNA have always added to the sum of what we are.

Part 1

1

Origins

ON ANY LONDON Monday morning packed trains rattle into King’s Cross, Euston, Cannon Street and Waterloo. The brakes hiss, the doors open and Saracens, Saxons, Berbers, Cave Painters, Vikings, Angles and Picts pour out onto the platforms. On any Saturday afternoon at Ibrox, St James’s Park, Old Trafford and Anfield crowds of Caledonians, Deer Hunters, Kurgans, Iberians, Rhinelanders and Anatolians roar on their teams, passionate in support, their sporting allegiances central to their identities. On any weekday morning all over Britain the school run delivers the children of the First Farmers, the Shell Collectors, the Foragers, the Shebans and the Yenesei to the gates of the playground.

These are the British, named by their DNA markers, all of them immigrants, all of them descendants of men and women from somewhere else, from the distant, shadowy millennia of deep time, the survivors of many epic journeys lost in the darkness of the past.

But now they are found, their stories lit by DNA, by the alchemical ability of geneticists to find traces of our history inside us, an immense story printed in the letters of our genome. DNA offers a new narrative, the unfolding – at last – of a people’s history of Britain, a story of all of us who live on these islands at the end of Europe.

The story of the discovery of DNA itself is much younger and in some ways no less dramatic. In February 1953 two excited young men burst into the Eagle pub in Cambridge and announced to the lunchtime clientele that they had discovered the secret of life. If an eyebrow was raised perhaps it was because this was the sort of declaration young men make after spending a few hours in a pub. But in this case it was no less than the truth. Francis Crick and James D. Watson were researchers at the Cavendish Laboratory at the University of Cambridge, and that morning they had completed a model of the molecular structure of DNA, a model they knew was correct, convincing in every detail.

Deoxyribonucleic acid is indeed the secret of life because it is the basis of heredity, a biochemical blueprint for reproduction. The DNA molecule carries the patterns for constructing proteins, the building blocks of our bodies and the machines that run the cells that make up our organs. Every living organism has DNA, from bacteria such as anthrax to a whale, from the tiniest aphid to a giant redwood tree.

When Crick and Watson created a wholly coherent model of the molecule and comprehended how it copied itself, the clouds of conjecture cleared and new scientific horizons opened. Their discovery enabled the creation of entirely new academic disciplines such as the science of molecular biology. How hereditary diseases and disabilities are passed on was at last understood. And by understanding the DNA of diseases, effective means of combatting them could be found. Once they were able to recognise what proteins were deficient or missing, biochemists could manufacture drugs to deal with what had long seemed incurable. The likes of insulin for the treatment of diabetes was made possible by Crick and Watson’s breakthrough.

When the two researchers pushed open the doors of the Eagle, they also wanted to celebrate a victory. They had won a race. Three universities had been competing to be the first to make what they all knew would be a momentous, world-changing discovery. At the California Institute of Technology the chemist Linus Pauling had adopted two approaches by developing techniques called X-ray crystallography and by building three-dimensional models. In 1951 he published his model of the protein, alpha helix. With all the resources at his disposal, it was surely only a matter of time before Pauling’s techniques led him to a similarly credible model for the structure of DNA, and following the research at CalTech, it was likely to be a helix, a spiral curve.

X-Ray Crystallography

When Wilhelm Röntgen discovered X-rays in 1895, fellow scientists understood them as waves of electromagnetic radiation, another form of light. At the same time, it was recognised that crystals were regular and symmetrical arrangements of atoms and when X-rays were directed at them, the effects were seen to be very revealing about their atomic structure. A helpful analogy is the way in which the waves of the sea strike a lighthouse to produce secondary circular waves. In 1912 a German scientist, Max von Laue, shone a beam of X-rays through a copper sulphate crystal and recorded its diffraction on a photographic plate. This was a very significant advance in working out the atomic structure of matter, and in 1914 von Laue won the Nobel Prize for physics. At Cambridge University, William Lawrence Bragg and his father, William Henry Bragg, developed Bragg’s Law, a method of connecting the scattering of X-rays with the structure of the planes within a crystal. It unlocked the atomic structure of molecules and minerals, and the earliest to be understood were those of table salt, copper and diamonds. The Braggs shared the Nobel Prize for physics in 1915, the only father and son ever to do so.

At King’s College in the University of London, two brilliant scientists were collaborating, but not happily. Maurice Wilkins was a New Zealander who took a physics degree at Cambridge before the Second World War. Seen as a brilliant young scientist, he found himself working on the improvement of cathode-ray tubes for use in radar during the Battle of Britain. Later in the war Wilkins worked in the United States and was involved in the Manhattan Project. When it became clear that the primary aim was to build an immensely destructive atomic bomb, Wilkins (along with many other nuclear physicists) decided to turn his mind to other projects.

The supervisor of his PhD at Cambridge, John Randall, had also withdrawn from the Manhattan Project and together they began to work on X-ray crystallography, first at the University of St Andrews and later at King’s College, London. Like Linus Pauling in California, Wilkins realised that these new techniques could be central to any understanding of the structure of DNA. There is a palpable sense of talented scientists turning away from the destruction of war to something more creative, optimistic and wholesome – the discovery of how life is made.

At King’s Wilkins was joined by a remarkable woman. Rosalind Franklin had also contributed to the scientific effort behind the Allied victory in the more mundane field of investigating the properties of graphite, work that would eventually lead to the manufacture of carbon fibre. After 1945 she gained valuable experience in X-ray crystallography at the Laboratoire Centrale des Services Chimique de l’Etat in Paris before John Randall brought her back to London to work with Maurice Wilkins on DNA.

The collaboration was not a success. Franklin and Wilkins disliked each other so much that the pace of their research slowed and academic plotting and bickering sometimes seemed more important. Rosalind Franklin’s response was to do her research alone, and from her notes it appears that she was closest to understanding the structure of DNA. Using diffraction techniques where a beam of X-rays is shone at a DNA crystal and the resulting reflections are captured as a series of dark or grey bands to produce an image, she successfully photographed the DNA molecule early in 1951. Analysis of the image clearly showed that it was a double helix, two spirals and not three as Francis Crick, James Watson and others believed it to be at that time. In her notes, Franklin wrote:

Conclusion: Big helix in several chains, phosphates on outside, phosphate-phosphate inter-helical bonds disrupted by water. Phosphate links available to proteins.

It was at this point embarrassment and academic pique came into play. Maurice Wilkins remembered James Watson sitting in a lecture given by Rosalind Franklin, ‘he stared at her pop-eyed and wrote down nothing’. That turned out to be a crucial lapse. Two weeks later Crick and Watson announced that they had understood at last how DNA was structured, but omitted to mention that their solution was partly based on Franklin’s lecture. The problem was that Watson had been forced to rely on his memory – and it turned out to be faulty. The model was structured around a value given by Franklin in her lecture and Watson had got it wrong. When she travelled up to Cambridge with her colleagues to see the new model, Wilkins recalled that Franklin ‘all but laughed out loud’. It was mortifying. Professor Sir Lawrence Bragg, the Director of the Cavendish Laboratory, was not pleased and he instructed Crick and Watson to suspend their research. DNA was clearly something King’s College understood far better.

This excruciating episode set a bitter tone. For a year Crick and Watson were frustrated, forced to work on haemoglobin (the protein that carries oxygen in our blood) rather than DNA. But then the instincts of competition came to their rescue. When Lawrence Bragg heard of the progress that Linus Pauling was making at CalTech, he changed his mind and asked Crick and Watson to revive their project. It was at this point human chemistry began to affect theoretical chemistry.

When James Watson went to London to meet Maurice Wilkins at King’s College, he found himself arguing heatedly with Rosalind Franklin. Immediately after this altercation, Wilkins took Watson into another room where, without her knowledge, he showed him Franklin’s latest and best images of DNA taken by X-ray crystallography. And around the same time more of her findings came into the possession of Crick and Watson. As a matter of routine, researchers at King’s College wrote short abstracts on the progress of their work and Franklin’s found its way quickly to Cambridge. It was not a private document and there was no suggestion of anything underhand but Franklin was apparently unaware that Crick and Watson had her research findings. ‘Rosy, of course, did not directly give us her data. For that matter, no one at King’s realised that it was in our hands’, wrote Watson some years later. In 1961 Francis Crick admitted that ‘the data we actually used’ was the work of Rosalind Franklin.

Soon after Wilkins showed Watson the latest images at King’s, Watson and Crick built their famous model. It resembled a twisted rope ladder with the uprights made from phosphates and sugars. But it included conclusions not visualised by Franklin. Francis Crick understood that the two helices, the spirals of DNA, twisted not in parallel but in opposite directions while Watson saw how the linked pairs of base compounds worked as the rungs of the rope ladder. This brilliant aperçu was the key to understanding how the molecule could copy itself, something even more critical than the structure itself. And when papers were published in the spring of 1953 in the leading academic journal Nature, only the three male scientists contributed and Rosemary Franklin was not acknowledged. In their famous, and very brief, article Watson’s American exuberance about what he had realised about how DNA copied itself was tempered by the English reticence of Francis Crick and it is the subject of one of the greatest understatements in the history of science: ‘It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.’

At first this earth-shattering discovery went entirely unreported. When Sir Lawrence Bragg announced at a conference in Belgium in April 1953 that his team had won the race to find the structure of DNA, there was no press coverage whatsoever. It was only when he spoke at Guy’s Hospital in London a month later that Ritchie Calder, fortunately a scientist himself as well as a journalist, reported the breakthrough made in Cambridge in The News Chronicle.

As Crick and Watson, and to some extent Wilkins, received plaudits, Rosalind Franklin began to realise that she was seriously ill. Suffering from an aggressive form of ovarian cancer, she died in 1958, aged only 37. But surprisingly she appears to have held no grudges and when in a period of remission, she stayed with Francis Crick and his family in Cambridge.

A Nobel Prize can be awarded only to the living, and in 1962 James Watson, Francis Crick and Maurice Wilkins shared the award for medicine. Perhaps if she had lived long enough, Rosalind Franklin might have been similarly honoured for her visionary work.

In the decade following the discovery researchers began to understand much more about DNA. Crick and Watson’s model showed how the DNA molecule unfurls, the rungs of the rope ladder separating down the middle into two half ladders, each with one rope and a half of every rung. Along with new phosphates and sugars to make the missing ropes of the ladders (as was mentioned in Franklin’s note of 1951), new bases are then added to each half, and in this way two are created from one – the secret of life.

There are four chemical bases making up the rungs of the ladder; adenine (A), thymine (T), guanine (G), and cytosine (C). Each rung is made up of two sorts of base pairs. Adenine will only link with thymine and guanine only with cytosine. DNA from every living organism has these same ingredients but what makes us different from turnips or spiders is the order or sequence of bases. This is called the genetic code and scientists read it in the letters of the nucleotides, A, T, C and G.

For the decade following the creation of Crick and Watson’s model, research concentrated on understanding how the body reads DNA to make proteins and how DNA is copied. The discipline of molecular biology developed quickly. But it was not until the 1960s that human population genetics began to evolve as a distinct academic discipline.

Born in Genoa in 1922 and having qualified as a doctor in 1944, Luca Cavalli-Sforza became interested in the new material on the analysis of blood groups in human populations that was published in the 1960s. It was not until the 1970s that the first sequences of DNA were read, but Cavalli-Sforza could see the value of using the classifications offered by blood groups. His aim was to use them to build evolutionary trees for Homo sapiens and to see how these linked and varied between different populations. But what puzzled him was the fact that blood groups were very much more diverse in Africa than they were over the whole of the rest of the world.

When scientists developed methods of reading the genetic code in the 1970s, it was at first a laborious and lengthy process and remained so until the early 1990s, but with the help of computing and other technological advances it accelerated and results began to appear quickly. Blood group classifications or markers were replaced by DNA markers. When all 6 billion letters of human DNA are copied in the act of reproduction, mistakes are occasionally made, and scientists noticed that some letters were out of place in a sequence. Because they are passed on to the next generation, these mistakes, these markers, allowed DNA to be used to trace lineages back into deep time.

Fred Sanger

Born in 1918 and raised as a Quaker, Fred Sanger was a conscientious objector during the Second World War, a time he spent not in prison but at Cambridge University where he began work that would benefit millions. Having completed his PhD in chemistry in 1943, he became fascinated by the problems of sequencing amino acids in bovine insulin. After a long string of spectacular success culminating in the award of a Nobel Prize in 1958, Sanger turned his mind to the sequencing of human DNA. With Alan Coulson and others, he ultimately came up with what is called the dideoxy chain termination method in 1977. A major breakthrough, it allowed long stretches of DNA to be sequenced quickly and precisely. In winning a second Nobel Prize (shared with two others) he joined Marie Curie, Linus Pauling and John Bardeen as the only double laureates in history. Having refused a knighthood because he disliked the idea of being called ‘sir’, Fred Sanger accepted the Order of Merit and allowed his name to be attached to the Sanger Institute near Cambridge, one of the world’s largest genomic research centres. Without his pioneering work, DNA sequencing would still be laborious, time-consuming and disablingly expensive.

Meanwhile an answer to Cavalli-Sforza’s conundrum about the diversity of African DNA was eventually supplied. It emerged close to Stanford University, where Cavalli-Sforza worked. At the University of California at Berkeley, a New Zealander of Scots extraction, Allan Wilson, was working on what he called the molecular clock. This was postulated as a means of dating the evolution of Homo sapiens, modern human beings, by looking at how DNA changed over time. Wilson and his team noticed that mitochondrial DNA, which is what women pass on to their children, mutated more readily and more regularly than the rest of our DNA. This made it easier to plot changes in mtDNA over relatively short periods of time, and not the millions of years of evolution conventionally envisaged.

This research led to a bombshell, and a solution to Cavalli-Sforza’s puzzle. In the early 1980s Allan Wilson announced the existence of the woman he called Mitochondrial Eve, the mother-ancestor of us all. Using the molecular clock, he believed that it was possible to estimate the time and place where modern humans first evolved. About 150,000 years ago, Wilson asserted, all of us, from Apaches to Aboriginal Australians, from Scots to Zulus, descended from one woman who lived in east-central Africa. The announcement of the findings caused a sensation, and a very attractive Mitochondrial Eve and an Adam found themselves on the cover of Newsweek magazine.

PCR, LSD and Non-PC

Kary Mullis is an unconventional scientist. In 1993 he shared the Nobel Prize for chemistry for his improvement of a vitally important technique known as polymerase chain reaction. But in his Prize Lecture, he told his astonished audience that the award didn’t make up for the fact that he had just broken up with his girlfriend. A year before he had started up a new business selling jewellery containing the amplified DNA of dead icons such as Elvis Presley and Marilyn Monroe. Mullis also reckoned that he would not have won his Nobel without the experience of taking LSD. Despite, or perhaps even because of these eccentricities, his improvements in PCR were epoch-changing. What Mullis was able to do was use an enzyme to bracket a DNA sequence and stimulate it to replicate almost an infinite number of times. This new technique had all sorts of applications and it allowed scientists to manipulate DNA to attack disease and to undertake complex research at much lower costs and achieve results quickly. It is a method used by all genotyping until very recently.

Wilson’s theory ran aggressively counter to the conventional multi-regional view that Homo sapiens had evolved in different places from slightly different origins. In Europe it was thought that humans descended from Neanderthals, in China from Peking Man and in Indonesia from Java Man. But the new research insisted that we all have African ancestors, and a great deal of more recent work has supported Wilson’s revolutionary view, although it is now recognised that a small proportion of the DNA of non-Africans descends from these other archaic humans.

Mitochondrial Eve is now thought to have lived approximately 190,000 years ago in east Africa, the area centred on modern Tanzania (although it must be added that evidence exists for a South African location for this prehistoric Garden of Eden, since the lineages of the Kalahari Bushmen and others are very ancient and very diverse). Fossil evidence confirmed the earliest appearance of modern humans, people who looked like us, at this time and as its techniques have developed, readings of DNA samples began to convert a theory into a fact. Researchers now believe that a man who might be called Y-chromosome Adam also lived in Africa, but not at the same time as Eve in a real version of the Garden. The ancestor of all men, traceable back through a Y-chromosome line, is thought to have lived some time around 140,000 BC probably in west Africa It is a misconception to believe that Mitochondrial Eve and Y-chromosomal Adam were the only men and women living at those times. Theirs are the only lineages that survive in the male and female lines, while others have died out. But it is, sadly, clear that Adam and Eve never knew each other.

Even Older

An ancient Y-chromosome lineage from Cameroon has been discovered in an African-American man from South Carolina and it matches that of four men from Cameroon. Labelled as A00, it appears to be very rare, but the startling finding is its date of origin. The oldest lineage was though to be A0 at c 140,000 BC, but researchers believe that A00 is much older, at c 237,000 BC. Work is ongoing.

As Cavalli-Sforza suspected from his study of blood groups, African DNA is much more diverse than anywhere else in the world, and many more markers are seen there. It seems certain now that the whole of the rest of the world was populated by men and women who walked out of Africa around 60,000 years ago. The probable reason for this ancient exodus is dramatic, emphatic.

In northern Sumatra the world’s largest island within an island is green with lush vegetation, and the steeply pitched roofs of its Batak people punctuate the horizon. Samosir lies in the middle of Lake Toba, the biggest lake in south-east Asia at 100 kilometres long and 30 kilometres wide. The sharply pointed gables of the lakeside fishermen’s houses mimic the prows of their boats and the brilliant greens of the scenery below are breathtakingly beautiful. But the beauty of the landscape is deceptive, for it is a memorial to a cataclysm.

Lake Toba shimmers quietly in the crater or caldera of a gigantic volcano. Some time around 73,000 BC, it suddenly exploded in a super-colossal eruption, an immensely destructive, climate-changing event, the largest anywhere on Earth in the last 25 million years. When Mount Toba blew itself apart, it may have obliterated life on our planet.

With a roar that must have been heard thousands of kilometres away, the volcano sent out 2,800 cubic kilometres of what geologists call ‘ejecta’. Around 800 cubic kilometres of ash rocketed into the atmosphere to create a vast black cloud. High winds whipped up by the eruption quickly blew the ash to the west, out across the Indian Ocean. The year of this nuclear explosion may be only approximately dated but the season is certain. Toba exploded in the late summer, for only the monsoon rains could have deposited such a heavy and rapid fall of ash over the whole of southern Asia. A layer 15 centimetres thick has been calculated but at one site in central India archaeologists have recently found the suffocating grey blanket at 6 metres in depth. The ash covered vegetation of all kinds and the long nuclear winter that followed killed it.

High winds also carried and dropped huge tonnages of ash over the South China Sea, the Indian Ocean and the Arabian Sea. By screening out the sun and poisoning the water, the fallout from Toba killed plankton, sea vegetation, fish and larger creatures. Geologists believe that an even greater volume of volcanic ash may have fallen over the oceans than the land, but the effect was no less cataclysmic.

Around 10,000 million tonnes of sulphuric acid were thrown up into the atmosphere and some of it fell as black acid rain and devastated plants, animals and people. Pumice also shot high in the air and when it fell on the ocean, it instantly solidified into vast white rafts between five and ten kilometres across. These were picked up by the tsunamis that radiated from Sumatra and smashed into coastlines thousands of kilometres distant.

As thunder boomed and the Earth shuddered, red-hot lava spewed and poisoned rain fell, the eruption continued for two weeks. Sumatra was incinerated and covered by 2,000 square kilometres of boiling lava before the hollowed-out sides of the volcano collapsed in on themselves to form the caldera, what would much later become a beautiful lake. The fires caused by the eruption blazed over a wide swathe and sent vast plumes of smoke into the darkening skies.

As far away as Greenland, geologists have detected in the ice cores an abrupt change in the Earth’s climate some time between 69,000 and 77,000 years ago. It can only have been caused by the destruction of Toba, and the cores show that what followed was indeed a long nuclear winter. A deadly sulphuric aerosol mixed with ash and smoke obscured the sun’s rays and temperatures plummeted, particularly in the first three months after the eruption. What extended this half-lit, grey winter was the way in which the sun heated the aerosol, ash and smoke so that it rose into the stratosphere where no rain could fall to wash it out. This almost certainly caused a long period of nuclear darkness lasting perhaps ten or fifteen years. People must have thought the gods were angry and that the world was ending. If nothing could grow through the ash-covered ground, then animals and people could not hope to survive. Mount Toba may have almost ended the history of human beings, almost made us as extinct as the dinosaurs.

But the ash did not fall everywhere, and the dark blanketing of the stratosphere cannot have been complete – for human beings did survive. And Luca Cavalli-Sforza and Allan Wilson’s research into African DNA suddenly appeared to connect with a recorded historical event. It seemed that the immense, world-wide destruction wreaked by the eruption of Toba was part of the reason why Homo sapiens and his (and her) origins are in Africa. It was the refuge where people survived the deadly fallout and the long nuclear winter.

Using computer models based on the number of markers seen in our genomes, geneticists believe that a tiny remnant, perhaps only 5,000 to 10,000 people, survived in the fertile rift valleys of east-central Africa. Other groups hung on in southern Africa and as far west as Cameroon. They can only have survived the horrors of Toba because the ash clouds and sulphuric aerosols did not obscure the sun completely and vegetation grew sufficiently for animals and people to carry on. Zoologists have noted that the East African chimpanzee, the cheetah and the tiger all saw their populations diminish drastically at this time, before they began slowly to recover.

As the Earth warmed and greened once more, the remnant groups across the continent also slowly recovered. They were hunter-gatherers who depended on a wild harvest of roots, fruits, berries, nuts and what animals they could trap or bring down, and because of their diet and way of life such communities could only grow very gradually. It may have taken many generations for there to be significant expansion, but after a time something surprising happened. A small group broke away from the east African communities and began to walk northwards. Perhaps only 300 to 500 people trekked out of the rift valleys. Geneticists are certain that the breakaway group was small because in their number only one mtDNA lineage that had descended from Mitochondrial Eve was present. All of the women in the world who are not Africans (and some who are Africans) are descended from this lineage, a marker labelled L3. And female descendants of L3, those in the two super-clusters of M and N, found across the whole of the rest of the world, are present in Africa now in only very low frequencies, and they appear to be recent arrivals.

A study led by Alon Keinan of Harvard Medical School suggests that more men than women walked northwards out of eastern Africa. By looking closely at variations in our X-chromosome and also at autosomal DNA, researchers have concluded that men were in a majority. No scientific reasons for this have been advanced beyond the sensible observation that in modern hunter-gatherer societies, women generally undertake short distance migration and men usually go on longer expeditions. It may be as simple as that.

After many more generations, the descendants of this small group reached the Horn of Africa, modern Djibouti. There the Red Sea narrows at the straits known as the Bab el Mandeb, the Gate of Tears. Now 15 kilometres wide and washed by treacherous riptides, it will have presented a much less formidable obstacle 60,000 years ago. Sea levels were lower then, the straits narrower and less deep, and there were small islands easily reached by rafts. A crossing could have been made in stages.

When our ancestors came ashore in the Arabian Peninsula, they stood on the edges of history. From these resourceful, curious, hardy and brave people the whole of the rest of the human race is descended. The DNA of all of us who are non-Africans was hidden in the genes of those who crossed the Gate of Tears and gained the farther shore.

2

Beyond Eden

AS ONE OF EUROPE’S youngest nations and one with an ancient imperial past, Italy was anxious for status. Britain, France, Germany and even Belgium had divided almost all of Africa between them and, apart from tiny Liberia, the sole remaining independent state was the Christian empire of Ethiopia. In 1889 the Italians agreed the Treaty of Wichale with Emperor Menelik II, the King of Kings, the Lion of Judah, the descendant of Solomon. Unfortunately, it lost something in the translation. In the Italian language version, clause 11 was clear. It stated that Ethiopia would henceforth be a protectorate, represented by Italy in all its foreign relations. In Amharic, clause 11 was not translated literally. In fact it was different, much softer, more palatable to the Lion of Judah, and it merely advised that Ethiopia could use Italy to represent it in foreign affairs – if it chose to. The discrepancy soon came to light, erupted into war and humiliation for the new kingdom of Italy at the Battle of Adowa in 1896 when Menelik II led an Ethiopian army to a stunning victory over the Italians.

Far to the south an Italian soldier was to die in an altogether nobler cause. Captain Vittorio Bottego was the first European to see and survey the spectacular River Omo, and he and his expedition followed its course to the delta where it joined the waters of Lake Turkana. The Omo rises to the north, at 7,600 feet in the southern highlands of Ethiopia and quickly falls to 1,600 feet at the level of the lake. There are dramatic waterfalls, and in places the river raises long stretches of white water in its headlong rush to the south. Towards its delta, where the flow slows and the banks are low, the Omo can be very dangerous. It is the feeding ground of crocodiles.

The Queen of Sheba’s Gold

Not only have geneticists discovered an mtDNA marker that arose in the biblical land of Sheba, archaeologists found the source of the queen’s great wealth. Her realm straddled the Red Sea, taking in parts of modern Ethiopia and Yemen and when she came to Jerusalem and the court of King Solomon, she brought 120 talents of gold. Estimates vary, but a talent weighed about 25 kilograms or more. That is a great deal of gold and Louise Schofield has found the remains of an enormous ancient gold mine in the former land of Sheba. On the high Gheralta plateau in northern Ethiopia in 2012, she found a monumental slab or stele carved with a sun and a crescent moon, ‘the calling card of the land of Sheba’. Then her team came across an inscription in Sabaean, the language the queen and her miners would have spoken. Known in Ethiopian tradition as Makeda, the queen ruled a civilisation that flourished for much of the first millennium BC and when she came to meet Solomon, she was said to have tested him with questions. Other accounts believe that the two monarchs became lovers and that the dynasty of Ethiopian emperors descends from their union.

Bottego was a cultured man, much interested in language and the peoples he encountered. He observed that the lower valley of the Omo lay at a crossroads in North-central Africa. At the northern end of the great Rift Valley, it was home to the Musi, Suri, Nyangatom, Dizi and Me’en peoples. All spoke different languages, and to Bottego’s eye, they exhibited different characteristics.

Having arrived on the banks of the Omo on June 29th, 1896, the Italian explorer led his companions northwards a few months later, planning to travel through Ethiopia. But Bottego had no idea that a bitter battle had been fought at Adowa and that his country was at war. In the Maji Hills, not far from the Omo, the captain and his 80-strong expedition were ambushed by a much larger force of Oromo tribesmen. Along with several others, Bottego was killed. News of his death only reached Italy two years later through two surviving members of the expedition. They had been captured and imprisoned on the orders of Menelik II for what they later described as ‘98 days of terror’.

Safely back in Italy, Lamberto Vanutelli and Carlo Citerni were greeted as heroes, and even in the twenty-first century commemorative sculpture was still being erected with much pomp and ceremony. The two men ‘narrated’ L’Omo: Viaggio di esplorazione nell’Africa Orientale. Much of it is concerned with surveying, mapmaking, geography and politics; the southern limits of Italian influence needed to be mapped before it could be asserted. But Vanutelli and Citerni recalled something else, something that would prove to be much more durable than Italy’s misplaced dreams of empire. The Omo Valley was like nothing they had seen before, at least in one remarkable aspect. The fossilised bones of human beings could be found there.

What revealed these deposits of our past was geology. Over aeons of time, many millions of years, the Great Rift Valley and the Omo Basin had convulsed with volcanic activity. Bulldozed by flowing lava, debris had been piled up all over the valley and all of this primeval fire and thunder created a layer cake of geological strata that, crucially, had been exposed by seismic faulting. And these layers, what would otherwise have remained buried deep in the ground, could be reliably dated.

K-Ar dating techniques measure the relative rate of radioactive decay of an isotope of potassium into argon and it is particularly accurate for periods far beyond the reach of other methods used by archaeologists, such as carbon dating. In the Omo Valley, where the layer cake had been helpfully sliced into sections by geological upheaval, the strata of volcanic tuff could be dated. And this in turn meant that the archaeology sandwiched between them, the remains of human fossils, could also be reliably dated.

In 1933 the discoveries of Vittorio Bottego and others were followed up by a French expedition led by Camille Arambourg. They mapped the area and recognised how important – and how extremely useful – the unusual geology of the Omo Valley was. During the Second World War the area was occupied by Allied forces who used the course of the river as a conduit to supply Ethiopian guerrilla units in their efforts to expel the Italian occupation.

Louis Leakey helped organise these supply lines. He was a remarkable man. Born in 1903, the son of missionaries, his first instinct was to follow their calling. But he became fascinated with the life of the Kikuyu tribe in Kenya, made himself fluent in their language, had a hut built at the bottom of his parents’ garden and went through a secret initiation ceremony. At the same time, this insatiably curious child became deeply interested in fossil-hunting, but before his passion could blossom further, Louis was sent to boarding school in England. From there he gained a scholarship to Cambridge University where he informed the authorities that his modern languages were Swahili and Kikuyu. By mistake he was invited to examine himself by conducting a viva voce. As an alternative, less partial means of validating his claims to fluency, Cambridge accepted an affidavit signed by a Kikuyu chief with a thumbprint. Having completed his studies, the young man longed to be back in Africa.

In 1931 Leakey led an expedition to the Olduvai Gorge in the eastern Serengeti Plains of what is now northern Tanzania. It was to become one of the most important prehistoric sites in the world, what newspapers would headline as ‘The Cradle of Mankind’. The fossilised bones of animals had been found there but Leakey was sure that human remains could also be uncovered. Olduvai had been the scene of controversy. In 1913, on the eve of world war, the German archaeologist Professor Hans Reck had found a skeleton that he believed dated to 600,000 BC. There was uproar. According to convention, man had been created long after that impossibly early date and Reck began to think that he must have been wrong. In any event, war intervened and the colony of German East Africa became British under the terms of the Treaty of Versailles.

In November 1931, Leakey took Reck back to Olduvai and allowed him the honour of entering the gorge first. Within a day, as he had predicted to Reck in Berlin, Leakey found stone tools, evidence that early man had lived at Olduvai. These tools had sharp, skilfully worked edges, and sceptics began to see that they had been made by intelligent beings and were not geological accidents. Moreover, the tools had been found nine miles from where the stone had been quarried and this showed the clear ability of their makers to plan and organise their activities. It seemed that the Olduvai skeleton found by Reck was no freak and had been correctly dated.

After the Second World War, Leakey became involved in politics, steering a difficult course between his empathy for and understanding of Kikuyu culture and the rise of the Mau Mau movement in Kenya. He came to know Jomo Kenyatta, the leader of the Kenyan African Union, and did what he could to mediate during the state of emergency.

Against this unstable background, Leakey and his wife Mary spent as much time as they could at the Olduvai Gorge. In 1959 excavations began on a stratum called Bed 1, and very soon Mary discovered a fossilised human skull. It was nicknamed Zinj. A year later geophysicists K-Ar dated Bed 1 and found that it was 1.75 million years old. It was a sensation. No one had expected early man to have been on the Earth for such an immensely long time, and the discovery of Zinj, scientifically and securely dated, showed that Darwin’s theory of evolution was no longer a theory.

The Leakeys became famous and their activities took place in a media circus with a constant stream of visitors. As more finds of fossils of early man were made Leakey’s sons, Jonathan and Richard, became involved. After the granting of Kenyan independence in 1963, Jomo Kenyatta became Prime Minister, and three years later the Emperor of Ethiopia, Haile Selassie, arrived in Nairobi on a state visit. Louis Leakey was invited to lunch and the conversation turned to archaeology. The emperor enquired as to why there appeared to be no fossils in his country and Leakey assured him that there were. The problem had been the intransigence of Ethiopian bureaucracy when permissions to explore the Omo Valley had been sought. Haile Selassie made those problems vanish and in June 1967 the archaeologists began work.

Despite the territoriality and squabbling between the different elements of what was an international expedition (there were French, American and Kenyan parties), and the fact that crossing the Omo was made very dangerous by swarms of Nile crocodiles snapping at the boats (Louis Leakey counted 598 in one day), the archaeologists made hugely significant discoveries. However to Richard Leakey, put in charge of the Kenyan group by his father, these were disappointing. His excavators found two skulls but the dating of a clutch of oyster shells found just above them reckoned that these human beings had lived around 130,000 years ago. They were far too young to interest Richard Leakey, not the sort of sensational discovery made by his mother and father at the Olduvai Gorge. But in reality what he had found was just as important. It was the earliest evidence for the existence of our species, Homo sapiens. In 2004 the strata around the original finds was re-dated and the results pushed back the origins of our earliest ancestors to c 195,000 years ago. It seems that modern human beings first walked under African skies, and that the long journeys of our ancestors began there. And, crucially, this archaeological evidence chimed precisely with what Allan Wilson discovered in the late 1980s through his DNA research and an understanding of the molecular clock.

Preserved in the strata of the Omo Valley was evidence of the environment our ancestors lived in, a powerful sense of how fragile their existence could be. Plant and animal fossils suggested a changing climate with dramatic swings from an arid, sun-baked bush country after 185,000 BC, and before then, a wooded grassland that was home to antelope and other grazing herds. At other times there was a dense riverine forest on the banks of the Omo where wild pigs rootled and browsed. Researchers also believe that there were montane forests in the highlands where the river rises. The evolution of wild pigs could be seen in their fossils and the sequence helped date the swings of climate change and set a reliable chronology.

Lake Malawi is one of the largest and deepest lakes in the world, and 700 metres down in its black-dark depths lie more clues that can piece together a picture of prehistoric African climate. Cores drilled out from the layers of sediment on the bed supply a clear linear record of what life was like around the shores of the great lake. It appears that between 135,000 BC and 90,000 BC tropical Africa experienced severe drought. The levels of Lake Malawi dropped drastically by 500 metres and the landscape around it resembled desert. It is likely that to the north and south the Sahara and Kalahari deserts expanded enormously at this time. In such a hostile environment, one that lasted for 45,000 years, it is very likely that populations of Homo sapiens were very much reduced.

Our ancestors were hunter-gatherers and the stone tools found in the Omo Valley and elsewhere suggest that they existed on a wild harvest of fruits, roots, berries, eggs and whatever animals they could trap or hunt down. They probably lived in family bands, some as large as 40 or 50 individuals, but these groups grew very slowly. Infant teeth almost certainly found the wild diet difficult and breast-feeding continued far longer than it does in modern societies. It could be four or five years before infants were weaned, and during all that time nursing mothers remained infertile. That in turn meant a long birth interval, and given the much shorter lifespan of women in prehistory, a likelihood of only three or four children, not all of whom would have survived.

Amazonian Mash

Isolated kindreds deep in the jungles of Amazonia, people who were pre-Stone Age and used bows and arrows and blowguns, have been documented as having larger families than the hunter-gatherers of Europe. Mothers had babies, toddlers and older children even though they were mobile and moved considerable distances in their wide ranges. Older children helped with their younger siblings and the food-gathering abilities of these peoples appeared to be unimpaired by having many children. They overcame the problem of soft infant teeth by boiling roots and making a mash by pounding them. Monkey brains were also given to toddlers for them to suck and mothers chewed tougher foods before spitting them into their babies’ mouths.

Hunter-gatherer populations not only expanded extremely slowly, they were vulnerable, wholly dependent on the natural world for food, shelter, tools and firewood. The swings of climate change seen in the cores taken from the bed of Lake Malawi (and confirmed by cores from Lake Tanganyika and Lake Bosumtwi) could cause populations to shrink dramatically or move long distances in search of better places to live. In the drought and desert conditions between 135,000 BC and 90,000 BC, there may have been only a few thousand of our species living in Africa.

At Jebel Faya in the United Arab Emirates, on the southern shores of the Persian Gulf, archaeologists have unearthed a puzzle. In an ancient rock shelter they discovered a set of stone tools: hand axes (flint stones with a sharpened edge but without a wooden shaft that could be held in one hand and used to chop), and an assortment of scrapers and burins or perflorators. This toolkit resembled artefacts found in East Africa in the rift valleys, the Omo and elsewhere, but their date seemed much too early.

Using a technique known as luminescence dating, researchers from the University of London calculated that the axes and tools from Jebel Faya were knapped and used some time between 125,000 BC and 100,000 BC. Their manufacture, by people who could be described as Homo sapiens, predated the exodus from Africa in 60,000 BC by many millennia and their findspot lay more than a thousand miles from the Bab el Mandeb, the straits at the mouth of the Red Sea.

Hans-Peter Uerpmann of the Eberhard-Karls University in Germany led an investigation into the climate of the Arabian Peninsula c 130,000 BC. Not only did he and his team establish that sea levels were much lower then, allowing an easy passage across the straits, but they also found that the desert climate of modern Arabia was very different in the deep past. Significantly greater rainfall watered a much greener land and fed a landscape of lakes and river systems. And so it seemed that while central Africa grew dry, arid and desert-like, plants and animals flourished in the Arabian Peninsula. It was an environment where Homo sapiens could also flourish.

More archaeology on the shores of the Persian Gulf is suggestive of a better life beyond prehistoric Africa. Jeffrey Rose of the University of Birmingham and his colleagues have come across a series of settlements on the edge of the Gulf that date to c 7,500 BC. They turned out to be a great deal more sophisticated than expected, with well-built stone houses, evidence of long-distance trade networks, decorated pottery, domesticated animals and the remains of one of the oldest boats ever found. Rose believed that these early farming settlements lay on the edge of a huge oasis, a land watered by the rivers Tigris and Euphrates that is now submerged under the waves of the Persian Gulf. Palaeoclimatologists reckon that this fertile oasis was dry land c 100,000 BC and Rose’s conjecture is that it may well have been home to a large population of Homo sapiens at that time.

Speleothems are mineral deposits found in caves. Perhaps the best-known varieties are stalactites and stalagmites. Formed by water seepage, they can act as a proxy record of climate change over long periods in the same way as ice cores. Researchers from the Hebrew University of Jerusalem have analysed speleothems from five caves in the Negev Desert and they are able to show that the weather was much wetter in that region between 140,000 BC and 110,000 BC. The Sinai-Negev landbridge between Africa and Near-Eastern Asia would therefore have been much more hospitable than the modern desert and would have allowed early movement of hunter-gatherer bands across it. At Skhul Cave in Carmel and Qafzeh Cave near Nazareth fossilised fragments of the skeletons of what appear to be Homo sapiens have been dated to c 100,000 BC. And it seems that all of these jigsaw pieces suggest that some of our ancestors moved north-east and east out of Africa long before Mount Toba blew itself apart c 73,000 BC.

However all that may be, the piecemeal evidence shows something unarguable: that human populations were fragile and very small, and more, that the present dominance of the Earth by our species was not inevitable. Indeed, climate change of the sort experienced by our remote ancestors may yet be our undoing.

When Toba erupted, it seems that these early pioneers on the Persian Gulf and what is now modern Israel did not survive the horrors of the nuclear winter that followed it. If there was an oasis in the Gulf, it lay close enough to the volcano to be badly affected and winds may have carried the deadly sulphuric aerosol mixed with ash and smoke north-westwards so that it darkened the lands of the Near East long enough to be fatal or provoke a trek back to Africa. As with much of our history, the movement of our species out of Africa may well be a story of advance and retreat.

After the cataclysm of Toba, the Earth’s climate recovered, and so did other humanoid populations. Our species was not alone.

In 1857 it was believed that The Missing Link had been found. When Benjamin Disraeli described it as ‘the link between apes and angels’, he wasted no time in memorably placing himself ‘on the side of the angels’. In the Neander Valley near Düsseldorf in Germany, quarrying displaced bones from a clay-filled cave in the steep sides of the ravine. Thought at first to be those of cave bears, they were retrieved and sent to Johann Carl Fuhlrott, a teacher and natural historian. He saw that the bones were in fact human and a year after they were found, descriptions of parts of what became known as Neanderthal Man were published.