The Incredible Human Journey (7 page)

In the 1950s ethnographer Lorna Marshall had spent several years with the Bushmen, and in her 1976 book,
The !Kung of Nyae Nyae
,
²
she had written:

I personally wish the !Kung could have remained as they were, remote, self-sustaining, independent, and dignified; but that is wishful thinking. Our modern society does not allow people to remain remote. Furthermore, many of the !Kung themselves want change; they want to have land and cattle like the Bantu.

The Bushmen were not ignorant. They may not have had televisions but they knew there was a wider world out there. I tended to agree with Arno. It was sad in many ways that this way of life was disappearing, but these were
people
, not museum exhibits – they had to be able to make their own choices. I felt very privileged to have visited Nhoma and learnt about their traditions, and I left wondering if I’d ever go back and, if I did, whether the Bushmen would still be there.

African Genes: Cape Town, South Africa

My first destination in Africa had provided me with insights into life in a contemporary hunter-gatherer culture, and the fragile nature of this way of life in the modern world. I had learnt about the deep roots of Bushmen ancestry and click languages, adaptations to endurance running in humans, and enjoyed an impromptu crash course in African beadwork. Flying from Nhoma to Windhoek to Cape Town, I was in search of more genetic revelations about African ancestry.

On a sunny spring day in Camps Bay, I met up with Professor Raj Ramesar, of the Cape Town University, to find out about the results of an ambitious study of the diversity of mitochondrial DNA among Capetonians.

In 2007, 326 Capetonians had volunteered to have their mtDNA sampled by the African Genome Education Institute, using salivary swabs to collect precious cells containing their genetic fingerprints. Cape Town is a cosmopolitan city. As well as a wide-ranging mix of Africans, people from other continents have also made Cape Town their home over the centuries. It’s a classic melting pot of cultures – and genes.

The results of the Cape Town study bore out that diversity. Everyone taking part in the study was asked what ethnic group they considered themselves to belong to. Of those people who considered themselves either white or coloured, 8 per cent had a maternal ancestry traceable to West Africa. This fits with waves of Bantu-speaking people moving down from the Niger region into southern Africa, bringing agriculture with them, starting around 3000 years ago.
¹
Among just the ‘white’ people, 3 per cent had black African mtDNA markers, and 10 per cent of black Africans had maternal lineages traceable not to Africa, but to Europe. Twenty per cent of black Africans had markers that went back to some of the earliest Africans: very early branches of the human family tree.

Ten of the original volunteers had assembled on the day I met Raj, and their maternal ancestry could be traced back to lineages originating throughout Africa, Europe and Asia. Firstly, Raj explained that the genetic markers used to construct the lineages actually represented tiny differences in DNA between people. ‘As different as we may look on the outside, we are practically identical at a genetic level,’ said Raj. ‘But the minor differences are what we use to plot population migrations from one part of the world to another.’

Then he revealed the results of the mtDNA tests to the volunteers. Some who felt themselves to be African through and through found they had maternal lineages on Asian and European branches of the tree. Of course, mitochondrial DNA reveals only a small bit of our ancestry: just the ‘motherline’. But nevertheless, there is still something quite profound about being able to trace part of your heritage back that far.

Although mtDNA traces only
one
line down through the centuries and millennia, among the many ancestors we all gather as we follow our family trees back through time, the study threw up some surprises for the participants involved. The results show quite graphically what a subjective and shifting concept ethnicity is. While similarities and differences between human populations are fascinating, the idea of ‘race’ doesn’t make sense in biology – it’s a concept pulled together from a ragbag selection of physical characteristics, culture and religion and attachment to place of birth. Ultimately though, however much we may feel that we come from a particular place, our genes show that our ancestry is far more diverse – and more interesting.

Rather boringly and predictably, I thought, my mtDNA was of European vintage. I was on the ‘I’ branch. But once I’d got over the lack of exotic genes in my motherline, I have to admit feeling a sense of wonderment at the revelation. Someone had managed to take some minute cells from my mouth, delve into my mitochondrial genome and pull out this fact about my ancestry. I know my family tree only back to my great-grandparents, going back perhaps two hundred years, but here was this piece of information, passed down to me from one of my very ancient female ancestors. It means my maternal ancestry goes back to the second wave of modern humans migrating into Europe around 26,000 years ago.
²

On the one hand, we can all trace elements of our ancestry back to a great range of places and times. But the mitochondrial DNA family tree also shows very clearly that, if we go back far enough, all the lineages converge – in Africa. In 1987, three geneticists at the University of California, Rebecca Cann, Mark Stoneking and Allan Wilson, published a seminal paper in
Nature
, reporting on an analysis of mtDNA from 147 people, and showing how their maternal lineages could be traced back to one woman, in Africa, some 200,000 years ago.
³
Since then, mtDNA from thousands and thousands of people has been analysed, and the tree has grown bushier, but the origin has stayed firmly anchored. If you traced your ancestry back far enough, along the ‘motherline’ (your mother’s mother, then her mother… and keep going), then eventually you’d get to a point where you reach a common female ancestor of
everyone
alive on the planet today. It’s not surprising that the geneticists have named her mitochondrial, or African, Eve.

How do we know she was African? Well, the highest density of branches, in other words, of different types of mtDNA, is in Africa. This is extremely strong evidence that all of us, our species, originated in Africa. And it’s not just mitochondrial DNA that reveals this pattern: the Y chromosome, and genes on other chromosomes, also show greater genetic diversity among indigenous Africans compared with Asians or Europeans.
⁴
All this genetic diversity points to Africa being the homeland of
Homo sapiens
. People have lived there longer than anywhere else, so there has been more time for mutations to accumulate and different lineages to sprout in Africa than on any other continent. In 2008, the results of the most detailed study of human genetic variation to date were published in
Nature
. Part of the study involved looking at more than half a million points in the nuclear genome, where the individual building blocks of DNA – or nucleotide bases – are known to vary, and comparisons were made between twenty-nine populations from around the globe. Analysis of the differences produced a tree, with branches spreading out from East Africa.
⁵

This genetic piece of the puzzle has not come as a surprise to most palaeoanthropologists; rather, it confirmed what they already suspected from the fossil evidence, because the oldest anatomically modern human remains come from Africa. However, there can always be arguments over the veracity of lineages reconstructed from fossils, because of the patchy and inconsistent nature of the evidence. The story we tell based on palaeontological, and indeed archaeological evidence, is woven together from fragments of information. The likelihood of material evidence, whether of people themselves or cultural objects, surviving for thousands of years and then being found, is minute. Many things made by Palaeolithic societies would have been organic, biodegradable, and so would have little chance of surviving. Very often, pieces of worked stone and waste flakes are the only objects left for us to find. Most skeletons will not become fossilised. They will get crushed or trampled or broken up and leave no trace. For a body to be preserved, it needs to get covered by mud fairly quickly, before it is ripped to pieces by scavengers. And the sediments it is sealed in need to be chemically and physically just right for any bones to be preserved. In many cases, water moving through soil will leach out mineral from the bones, and bacteria will eat away at the protein part of the bones, until virtually nothing is left. In a few lucky cases, the shape of the bone is preserved, while the substance of the bone changes as it exchanges minerals with the surrounding sediment – and it turns to stone, in a word: fossilises.

Even if something is preserved for all that time, there is no guarantee that it will be found. Some fossils and archaeology will be buried deep under metres and metres of sediment, or are in very remote places. Most ancient fossils or archaeological sites are discovered by chance. Often, it is human intervention that lays bare the evidence, through mining, quarrying or road-building, for example. At other times, natural erosion might reveal long-buried fossils. And when that evidence becomes accessible, it still may not be recognised.

Although archaeologists and palaeontologists do try to direct their attention to areas where they think there is a likelihood of finding evidence, sometimes the first clues that lead to significant discoveries are entirely serendipitous.

With all this chance and uncertainty involved in fossil-hunting, it is astounding that fossils have been found, in Africa, that seem to go right back to the dawn of our species.

The Earliest Remains of Our Species: Omo, Ethiopia

For several decades two sites have vied for primacy as containing the most ancient fossils of anatomically modern humans. Both these sites are in Ethiopia: Herto and Omo Kibish.

In 1967, a team led by Richard Leakey had unearthed modern human fossils – two skulls and one partial skeleton – from the Kibish formation in the Omo Basin in Ethiopia. Uranium series dating of mollusc shells in the sediments suggested the fossils dated to around 130,000 years ago. Thirty years later, the fossilised skulls of one juvenile and two adult modern humans were discovered in Herto, in the Middle Awash area of the Afar depression. The skulls looked modern in many ways, but were quite robust. The authors, presenting their finds in
Nature
, described them as being ‘on the verge of anatomical modernity but not yet fully modern’. The Herto fossils were dated to 160,000 years ago by argon-argon dating.
¹

But in 2005, new – much earlier – dates were published for the Omo skeletons. A team of geologists and anthropologists, led by Ian McDougall from Australian National University (ANU), revisited the site where the Omo fossils had been discovered. Using site records and photographs, they were able to pinpoint the exact locations where the fossils had been found. At the Omo I site, confirmation that they had indeed located the precise findspot came when they discovered additional fragments of fossilised skull that fitted into gaps in the original finds.
²

Both sets of human remains, although found on opposite sides of the Omo River, lay in the same stratigraphic layer. And this layer was sandwiched neatly between two strata formed of volcanic tuff, from the eruptions of ancient volcanoes. This was highly convenient, because tuff is amenable to dating using argon isotopes.

It turned out that the deeper layer was laid down some time after 196,000 years ago, while the higher layer dated to, at most, 104,000 years ago. The layer in which the human fossils were found lay
just
on top of the deeper tuff. McDougall and his team argued that the fossils were therefore almost as old as this deeper layer of volcanic tuff, at around 195,000 years old. This new date made the Omo fossils the oldest anatomically modern human remains – in the world.

The fossils themselves resided in Addis Ababa Museum, but I wanted to see the place where they had been discovered. It felt like a pilgrimage, and in a way it was: I was going to visit our ancestral home. I had read Richard Leakey’s books as a teenager, and I couldn’t quite believe I was about to get the chance to visit the places I had read about. The names attached to this landscape seemed epic, even mythical, to me: the Rift Valley, the Omo River, Lake Turkana. But they are real places. However, I was travelling to one of the most remote parts of Africa, and finding the precise place where the fossils were discovered wasn’t going to be easy.

On a Monday morning, I set off from Addis Ababa in a small Cessna Caravan, headed for Murule camp (and the closest airstrip to the Omo findspots), piloted by Solomon Gizaw. It was cloudy when we took off, but it soon cleared, and we were flying south-west over green countryside with irregular fields and round, thatched houses of small farming communities. From the air the thatched houses looked like clusters of brown mushrooms. It was clear that agriculture was dominated by small-scale farms, and Solomon was outspoken about the inefficiency of food production in Ethiopia. ‘We have so much good land. There should be more than enough to feed everyone,’ he said. ‘But it is not managed properly.’ Certainly the land beneath us looked green and fertile. It was a very different view of Ethiopia from the terrible pictures of the famine in the 1980s. But there was also little in the way of infrastructure; I couldn’t see many roads. It must have been extremely difficult to reach people out in rural areas when there was a food shortage.

As we flew over the mountains, Solomon explained that we were into coffee country. So when we stopped off to refuel at Jima, I refuelled with some local coffee. The café at the airport was a wooden shack with a corrugated iron roof. Inside, a group of men were playing draughts using a home-made board and bottle tops for pieces. A woman with a beautiful, serene face came over, holding high a tin kettle, and poured a stream of strong, sweet coffee into my china cup.