The Journey of Man: A Genetic Odyssey

by Spencer Wells

  So, both the Y-chromosome and the mtDNA paint a clear picture of a coastal leap from Africa to south-east Asia, and onward to Australia. Taking the genetic dates as a guide, modern humans could have made this journey around the same time as the earliest archaeological evidence pointing to human occupation in Australia. DNA has given us a glimpse of the voyage, which almost certainly followed a coastal route via India. But is there any archaeological trace of this journey along the route?

  A swim in Ceylon

  This brings us back to the issue of the dating, particularly as applied to the Australian remains. No evidence for other hominids has ever been found in Australia – Homo erectus did not make it across the long stretches of open ocean that separated it from south-east Asia, despite living only a few hundred kilometres away in Java. Because Homo sapiens is the only hominid species that has ever been found in Australia, any evidence of human occupation sticks out like a proverbial sore thumb. Stone tools unearthed in Arnhem Land could only have come from one source – us. And if the radiometric dates say that stone tools were present in Australia 50–60,000 years ago, almost immediately after the genetic dates show us that our ancestors were still in Africa, this means that modern humans must have made use of a route that afforded extremely rapid movement. The coastal superhighway seems to be the most likely one.

  As we have seen, though, there were other hominids living along the route followed by these beach dwellers. They also made stone tools, and these have been found throughout Eurasia. The easternmost extension of the range of Homo erectus was Java, and it is possible that they even survived until around 40–50,000 years ago – long enough for the coastal migrants to have encountered them as they moved through the Indonesian archipelago. It is clear, though, that they must have become extinct almost immediately after the arrival of the Moderns, if not before. What is uncertain is whether we actively forced them out of the picture – a genocidal scenario that we will explore in greater detail when we get to Europe later in the book.

  In the same way that extinct hominid species can be recognized by the size and shape of their bones, so too can tools and other artefacts be classified according to their style. I like to draw a parallel with the evolution of that icon of American culture, the Coca-Cola bottle, during the twentieth century. During the first seventy years of the century, the bottles were 8-ounce glass sculptures, with a distinctive curved shape that still evokes 1950s soda fountains and drive-ins. During the 1970s, a larger, lightweight plastic bottle was introduced to supermarkets – but it retained its hourglass shape, as though harking back to the bygone era of the earlier version. By the 1980s, though, the curves had been dropped in favour of a standardized, flat-profile plastic bottle now used by all drinks manufacturers. There is minor size variation – 2-litre juggernauts are common in the UK and America, while continental Europe opts for a slightly more elegant 1.5 litres – but the new style has become universal.

  This progression of a universal form is seen for all human tools, from hammers to knives to guns to sauté pans. Everything evolves over time, and the most efficient form finds the most widespread application. It quickly dominates over competing forms, and eventually makes it difficult to remember the styles that were in use before. Even before the current era of globalization, the world had its ‘killer apps’ that dominated everything else. In the case of the period we are talking about, 50–60,000 years ago, the killer apps are grouped into a common cultural phenomenon known as the Late Stone Age, or more technically, the Upper Palaeolithic. The tools of the Upper Palaeolithic mark a radical departure from those that pre-date them, and are clear evidence for the presence of anatomically modern humans, as opposed to Homo erectus or Neanderthals, who remained trapped in a Middle Palaeolithic time-warp.

  The details of the Middle to Upper Palaeolithic transition will be examined in the next chapter, but for the purpose of the story of our Australian coastal dwellers it is sufficient to say that the earliest Upper Palaeolithic tools mark the initial migration of modern humans into any geographic region. And that is why India is unusual, since there is actually very little evidence of the Upper Palaeolithic there. There is a general dearth of human remains from all periods leading up to the Upper Palaeolithic, but at least there are abundant tools from the earlier periods. The Upper Palaeolithic provides no telltale signs until very late in the day, and even then they show up in an unexpected place.

  Fa Hien cave in Sri Lanka provides us with the earliest sign of the Upper Palaeolithic in the Indian subcontinent. The date, however, is a problem – the earliest clearly modern artefacts date from no earlier than 31,000 years ago. Nearby Batadomba Lena cave contains the earliest skeletal material from anatomically modern humans, also dating from around 30,000 years ago. The combination of age and location gives us two clues in our search for traces of the coastal migration. First, the Sri Lankan caves suggest that the earliest modern humans arrived in India from the south, rather than from the north via the more obvious inland route. This implies that they were living on the coast, consistent with the theory of an early coastal migration.

  The second clue, which comes from the date, is that the Batadomba people could not have been the ancestors of the Australians, since they actually lived over 20,000 years after the earliest evidence for human settlement in Arnhem Land. Another curly one. It may turn out that archaeological layers below those already excavated will yield earlier evidence for modern human presence, but for the time being it appears that Batadomba is too late to help us along on our voyage. In fact, late dates are found along the entirety of our coastal route to Oz. In Thailand, for instance, there is evidence for modern human occupation from about 37,000 years ago at Lang Rongrien cave – but not before. As we move closer to the scene of the crime, the dates get older – advanced, Upper Palaeolithic stone tools dating from 40,000 years ago have been found at Bobongara, on the Huon Peninsula of eastern New Guinea. This would have been the final stepping-stone on the journey, but there is still nothing approaching the 50–60,000-year-old dates in Australia. Thus, in spite of the genetic pattern tracing an early coastal route out of Africa, the archaeology appears to have failed us. Where is the evidence for our coastal route?

  Unfortunately we don’t know, but there is a likely hypothesis. Since almost all archaeological work today is carried out on land, we are probably missing the artefacts that are hidden underwater. ‘Rubbish – surely Atlantis is a myth!’ you might be saying. Well, yes and no. While the evidence for an entire civilization falling catastrophically into the sea is fairly sparse, what is unequivocal is that sea levels have indeed fluctuated substantially – if somewhat more gradually – over the past 100,000 years. Those of 50,000 years ago were around 100 metres lower than they are today, as large amounts of moisture were tied up in the expanding ice sheets of the northern hemisphere. This may not sound like much of a difference, but remember that we are not as interested in the depth as we are in the extent of the land that would have been exposed by these fluctuations. Since the continents typically have very shallow slopes as they fall off into the sea, a difference of 100 metres can make a huge difference in the amount of land exposed. For example, a drop in sea level of this magnitude would expose as much as 200 km of land off the west coast of India. Sri Lanka and India would have been connected by a land bridge, the Persian Gulf and the Gulf of Thailand would have been fertile river deltas, and Australia and New Guinea would have been two bulbous extremities of a single landmass. All in all, our entire coastal route would have been much different 50,000 years ago.

  What the recent sea-level rise means is that, if our coastal voyagers were living primarily off resources provided by the sea, the places where they chose to live would have been those that are now underwater. The Y-chromosome pattern in Eurasia shows that our M130 coastal marker is found predominantly in the southern and eastern parts of the continent. Furthermore, M130 chromosomes in the south appear to be older than those found further north, suggesting a later migration or
iginating in the tropics. These results, coupled with a lack of archaeological evidence for modern human occupation until after 40,000 years ago, suggest that the early coastal migrants did not stray far from the sea. Adapted to a coastal lifestyle, the surfers do not appear to have made significant colonial forays into the turf. Knowing this, it would seem more appropriate for archaeologists in search of the first Indians to be wearing scuba gear rather than pith helmets. It is likely that the earliest Upper Palaeolithic tools in the subcontinent will be found underneath thousands of years’ worth of sand and coral growth.

  Australian Ararat?

  Laura, a small town 300 km north-west of Cairns in Queensland, is known for two things. It was once a regional headquarters for the Cape York gold-mining industry, and as such it embodied the brutality of European settlement there. Much more important to the Aborigines, though, is the fact that it is the site of the Laura Festival of Aboriginal Art and Culture, held biennially in a large field on the outskirts of town. It may seem somewhat surprising that this major international festival is held in a location that, until recently, had no paved road connecting it to the rest of the world – and one with such a legacy of colonial exploitation. Laura was chosen, though, because it is in fact the location of several sacred aboriginal sites, decorated with over 15,000 years’ worth of detailed artistic depictions on the boulders surrounding the town. The art is guarded by spirits known as Quinkans, named Timara and Imjim, who act as a kind of collective conscience. Timara is the more devilish of the two, serving to keep the population in line, while Imjim – who is characterized by a bulbous penis in his portraits – is rather more Puckish, and enjoys playing practical jokes.

  The Quinkans, and their ancient pedigree, demonstrate the strong sense of connectedness that the Aborigines feel to the land where they live. Their songlines trace ancient journeys across the landscape, providing a genealogical link back to the earliest days of human existence. Like many indigenous peoples around the world, the Aborigines believe that they have always lived in their land. They cite the scientists’ ever-changing estimates of the dates of human occupation, which have increased steadily over the past half-century from a few thousand years in the early 1960s to as much as 60,000 years today. As new dating methods – each with their own sources of error – have been applied to Australian prehistory, they have extended the age of human occupation there. As we’ll discover, evidence for modern human occupation in Europe does not pre-date 40,000 years ago, meaning that Australians certainly have a much more ancient connection to their homeland than the Europeans who colonized their continent over the past 200 years.

  The genetic results, though, clearly show that Australians – like everyone else alive today – trace their ancestry back to Africa. The Australians have an answer for this. Greg Singh, an aboriginal artist living in Cairns, suggests that the world was actually settled from Australia, explaining the genetic connection between the Oz and Africa. He claims that, as with radiocarbon dating methods giving way to thermoluminescence, so too will a reassessment of the genetic data provide evidence for the centrality of Australia in world genetic prehistory. This is clearly impossible – Africa is unequivocally where our species originated – but we could ask if the route leading to Australia, which delineates the earliest territory to be settled outside Africa, acted as a kind of prehistoric Ararat. Was the coastal route a staging post for the settlement of the rest of the world? If Africa was first, could Australia or south Asia have been the main conduit through which the rest of our journey flowed?

  To find the answer to this question we will have to return to Africa, in search of the other main line of human genetic diversity.

  * Of the three Y clusters tracing their descent from M168, only two will be examined in this book. The third, found mainly in Africa, is defined by a marker known as YAP or M1. Outside Africa it splits into two lineages, tracing essentially the same migrational routes as the other two Y clusters described in the text. Because it adds little to our understanding of the ‘out of Africa’ migrations, and is rare in most non-African populations, I have chosen to ignore it. My apologies to Mike Hammer, who discovered the YAP marker in the early 1990s.

  5

  Leaps and Bounds

  Language is the dress of thought.

  Samuel Johnson, Lives of the English Poets

  My Y-chromosome is defined by a marker known as M173. What this means is that at some point in the past, a man – one person – had a change from an A to a C at a particular position in the nucleotide sequence of his Y-chromosome. This man could, in fact, be called M173, after the marker. All of his sons also carried this marker, marking them uniquely as his male descendants. They in turn passed it on to their sons, and over time it increased in frequency. Today, M173 is very common in western Europe, where my male ancestors come from – over 70 per cent of men in southern England have it, showing that we all have the same recent ancestor. But this is not the only marker I have – if I trace my genetic lineage back in time, I also have additional polymorphisms with names such as M9 and M89 – each one a unique change at a different position in my Y-chromosome sequence. I also have the marker M168, which places my ancestors, like those of every other Eurasian, in Africa around 50,000 years ago. The order of these markers allows me to trace the journey taken by my ancestors to the British Isles over the past 50,000 years – and exposes some fascinating relationships among people around the world. Of course, this same exercise can be repeated for every man alive today. It is a bit like deconstructing the bouillabaisse recipe passed to me by my parents and tracing back through each of the ingredient changes made by preceding generations to the ultimate source of the recipe – the original African soup.

  We saw in the preceding chapter that one marker, M130, defines he majority of men living in Australia. It traces back to Africa, sharing a common ancestor with my Y-chromosome when we reach M168 – our Eurasian Adam. The limited distribution of M130 in populations around the world reflects its coastal journey out of Africa, skirting along the south of the continent, leaving tantalizing traces of the trip along the way. But were they accompanied by men carrying M89, the next marker on my lineage? Did the journey into Eurasia begin 50,000 years ago on the south Asian coast?

  Before we can answer this question, and begin to dissect the Eurasian soup recipes beginning with M89, the ancestor of most non-African Y-chromosome lineages, we need to ask a vitally important question: if – as all of the archaeological evidence suggests – modern humans were present in Africa by 150,000 years ago, why did they wait so long to leave?

  Mental gymnastics

  The sun is going down on the east African savannah and it is starting to get noticeably colder. You shiver, relieved that you and the other members of the hunting band managed to kill a lame gazelle. The clan will eat well tonight. When you return to camp, everyone takes a simple stone cutting tool – sharp on one edge and blunt on the other – and butchers the animal. The tool, which anthropologists today would classify as Mousterian (Middle Stone Age), is simple but effective. You make quick work of the sinew and bone and soon you are relaxing around the fire, watching the meat cook over the flames. A hyena howls in the distance and you begin to think about other things for the first time in hours.

  As you mull over the day’s hunt you are thankful that your luck has held out again – the animal herds do seem to be getting sparser. Of course you don’t know it, but the African climate has been getting drier, and the resources to support the herds are simply not as common as they used to be. After dinner your mate brings your son to you. Although he is a strong, healthy child, he worries you because he seems so unlike the other children. For one thing, he has already learned to speak – at age two – while the other children do not do this until they are at least three. He also seems to be much better at making things than the other children in the clan, and enjoys playing games with the small pieces of stone that lie scattered around the camp. He seems much more emotional than the others,
often erupting into violent temper tantrums that scare the other clan members. The strangest thing, though, is that he has begun to trace images in the dust that are similar to the animals that you bring back to camp. You find this especially frightening, and quickly rub them out when you see them. Others in the clan have noticed, though, and there have been some mutterings about his unusual behaviour.

  Time passes. As your son grows up you teach him to hunt and make simple tools, hut his knowledge soon surpasses yours. He seems to have a magical ability to anticipate what the animals will do, which makes him a popular member of the clan, in spite of his odd behaviour. At an early age – around fifteen – he becomes the accepted leader of your small group. Under his guidance your clan eats well and prospers. He fathers many children, and they too seem to be much cleverer than others in the group. Within a few generations all of the members of the clan can trace their ancestry to him. He becomes the ‘totemic ancestor’ of the group – the founding father – and everyone descended from him is by definition a member of the group. Other clans, denied the mysterious knowledge of animal behaviour and superior tool-making ability that give his clan such an advantage on the hunt, either move away or are disbanded in raids organized by the clever ones. The women are taken by the raiders and are incorporated into the clan structure, but the men are usually killed or chased away. Soon there are too many clan members to live in one small territory, and in the ensuing arguments over access to food some of the young men take their mates and set off to find new territory. The process is repeated many, many times over the next few thousand years, until essentially every man in the region traces his ancestry to that first, clever child.