Homo Britannicus
Page 11
So let’s see what evidence there is for human occupation in Britain between 400,000 and 70,000 years ago and then we’ll examine what factors might lie behind the pattern. The glacial period that followed the rich sites of the Hoxnian, matching Marine Isotope Stage (MIS) 10, has no definite archaeology associated with it, but after that evidence reappears in Essex, on the opposite side of the Thames estuary from Swanscombe. At Purfleet, research since the 1960s in four now disused chalk quarries has given us a rare glimpse of human activity in Britain during the interglacial period represented by MIS 9, around 320,000 years ago. The deposits in question are some 8 metres thick and lie on ancient chalk bedrock, accumulated on one of the ancient Thames terraces when the river meandered north of its present course, and was actually running south-westwards at this location as it formed a huge reversed S-bend. Because of their relatively low altitude, the deposits were considered for many years to date from only the last interglacial, but fossils and archaeology both seemed to contradict this, and it has taken much careful work by geologists and palaeontologists, including members of the AHOB team, to establish their real age.
The sequence at Purfleet begins with a surface of frost-shattered chalk from the arctic conditions of MIS 10 about 350,000 years ago, followed by river gravels, sterile of fossils and artefacts. The next bed was laid down in a fast-flowing river with shells that indicate the climate was now warm, and the first artefacts appear, simple flakes and the cores from which they were struck. There are also remains of fallow deer, a species found in warm woodlands. The succeeding deposit is finely layered, suggesting tidal mudflats, followed by sands packed with freshwater shells, bones and occasional stone tools. These two beds clearly reflect a climate at least as warm as southern Britain today. There are fish such as carp and pike, lizards and snakes, and amphibians such as green frog. The small mammals include white-toothed shrew, water shrew and water vole, while large ones include fallow deer, roe deer, beaver, macaque monkey and straight-tusked elephant. The presence of monkey may seem surprising, but it was still common in southern European woodlands at this time. Tree and grass pollen suggest mixed oak forests with open areas, perhaps due to the river or to grazing or browsing by large mammals. Succeeding sands and gravels indicate strong river currents and contain some handaxe tools, but far fewer fossils. Finally, the river deposits show the arrival of more open conditions (there are fossil horses), and a new technology at the transition to the glacial conditions of MIS 8. This new technology is called Prepared Core or Levallois, after the suburb of Paris where it was first recognized in Palaeolithic tools over a century ago, and we will discuss its implications next.
Up until this time in the Palaeolithic, there were two foci in stone toolmaking. The core would be used to produce flakes, and both might be utilized. In the earliest stone tools, one or two flakes were struck off a pebble to produce a basic cutting edge and convert the pebble (the core) into a chopper (the tool). The flakes that had been struck off, with their simple sharp edges, might themselves also have been used as cutting tools. As the Palaeolithic progressed, handaxes began to be made in many parts of the western Old World, and here it seems that the toolmaker was most interested in the final form of the core, purposefully trimming off flakes on alternate sides of the core until the desired shape of handaxe was obtained. Although many flakes were also produced, they seem to have been less important. In Prepared Core (Levallois) technology, by contrast, the form of the flake to be produced dominated the process. First the edges of the cobble were knapped to give a rough oval shape, and then the upper surface of this core was trimmed. Next a large flake was removed across one end of the core to produce a flat striking platform. Finally, the end of the core was struck at right angles to the prepared platform, detaching a single flake off the core. The core itself is often called a tortoise core because of its resemblance, after the main flake had been detached, to a tortoise shell. There seem to have been two particular advantages to this technique. If the process worked successfully, the shape of the flake was predetermined, and a more usable cutting edge could potentially be produced from a core of given size. In addition, the long thin flake produced could easily be modified to produce a handaxe, a knife or a spear point.
The Prepared Core technique was so successful that it dominated toolmaking for the next 250,000 years in Europe, western Asia and Africa. Neanderthals and early modern humans used it throughout the Middle Palaeolithic, and because it forms a common heritage of these two groups it has led to a theory about its origins and their evolution. Two researchers in Cambridge, Robert Foley and Marta Lahr, have developed what is called the Mode 3 Hypothesis (Mode 3 being another name for Prepared Core/Middle Palaeolithic industries). They have argued that the divergence between Neanderthals and Homo sapiens occurred around 250,000 years ago, following the development of Mode 3 (Prepared Core) technology. They relate this archaeological innovation to African populations of about 300,000 years ago, who invented the technique and then spread successfully across Africa, into western Asia, and then Europe. Those who stayed behind in Africa evolved into the first modern humans, while populations who spread into Europe replaced earlier humans (such as the Boxgrove and Swanscombe people) and evolved into the Neanderthals. However, there are serious problems with the Mode 3 Hypothesis. First, in Europe, there is little sign of an intrusive migration. Instead it seems much more likely that the roots of both the Neanderthals and their Prepared Core technique are local. As we saw in Chapter 3, the Swanscombe and Atapuerca Pit of Bones people date from about 400,000 years ago, and are associated with handaxe tools. Yet both show signs of Neanderthal features, and can broadly be considered as Neanderthal ancestors, local to Europe and well before the date of the supposed migrations of tools and people ancestral to Neanderthals from Africa. Second, it is not clear where the Prepared Core technique originated, and it is possible that it spread through existing populations without replacement, or evolved in several regions independently, rather than spreading with a migrating wave of people.
Moving on to the mammals of Purfleet, these have been important
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in the recognition of the Purfleet Mammal Assemblage-Zone, which can be distinguished from the earlier Swanscombe Mammal Assemblage-Zone of 400,000 years ago by the presence or absence of certain diagnostic species. For example, an extinct small mole and giant beaver, rabbit, and European pine vole are all present in the earlier interglacial but not at Purfleet, while hyaena is known from Purfleet but not from the Swanscombe interglacial (the Hoxnian). Similarly Purfleet can be distinguished from later interglacials by species like the macaque, which is not known in Britain after this time. Moreover, similarities in mammals, pollen and other indicators suggest that further Essex sites such as Grays Thurrock and Belhus Park near the Thames, and Cudmore Grove near the River Blackwater, also belong to the Purfleet interglacial of about 320,000 years ago. Purfleet also has a special archaeological importance in its succession of artefacts, recording a sequence going from what looks like a Clactonian industry, without handaxes, through handaxe levels, and finally the appearance of Prepared Core artefacts. This suggests that the region remained important to humans through a considerable period and through marked changes in the climate and landscape.
The Purfleet archaeological record is significant because, in the apparent succession from Clactonian to handaxes, it duplicates what was recorded in the previous interglacial at sites like Swanscombe. We discussed the different ideas to explain the Clactonian/handaxe contrast in Chapter 3, and the recurrence of this pattern may support the idea that different populations were involved. If this is so, as Britain warmed up in both interglacials, the first wave of colonizers were the Clactonians, and people making handaxes followed them. We do not know where either group came from, but perhaps the Clactonians were geographically closer to Britain, more mobile, or more suited to the plants and animals of the early part of the interglacial. Whether the Clactonian people subsequently died out, migrated, or we
re replaced or absorbed by the handaxe makers, we do not know, and unfortunately we have no remains to show what they looked like in comparison with the Swanscombe fossil. In turn, during the Purfleet interglacial, the handaxe makers developed into, or were replaced by, people making Prepared Core tools. But these people were now struggling in the face of changing conditions, as the Purfleet interglacial drew to a close. Human visibility once again shrank to virtually nothing. One handaxe site, at Harnham near Salisbury, has recently been discovered and dated to the following cold stage, but otherwise we pick up the signal again about 100,000 years later, in a rather surprising place – North Wales.
The early Palaeolithic of Wales is hardly represented at all. While over 100,000 handaxes are known from England, there is only a handful from Wales, with one notable exception – Pontnewydd Cave. Part of the reason for the lack of tools in Wales must be the dominant highland terrain of the country, where repeated glaciations have destroyed the evidence, except in special cases such as Pontnewydd. Pontnewydd (New Bridge) Cave lies about ten kilometres inland, south of the seaside town of Rhyl and the broad Vale of Clwyd, in the lush Elwy Valley. The cave was mentioned by a Reverend Stanley in 1832 who had dug in the nearby Cefn Cave and he reported, ‘I found [it] to be entirely blocked up with soil, and [it] has clearly never been open to human observation. But I have no doubt, from its appearance and character, that it will… exhibit as rich a prospect [as Cefn], whenever its recesses may be explored, in search of those organic remains now unknown in the temperate zones.’ Forty years later Professor William Boyd Dawkins described his excavations with two local amateur prehistorians, which supposedly yielded fossil remains but no artefacts. However, later sorting of the large spoil heaps he left behind revealed many stone tools and animal bones that were missed in 1870. Soon afterwards, the geologist McKenny Hughes carried out more careful excavations and not only found fauna and artefacts but also a large human molar tooth. The anatomist George Busk, whom we met in the Introduction as someone who studied the Neanderthal skull from Gibraltar, examined it in 1874 and said it looked ‘quite as ancient as the rest’. It was thought to date from the last glacial stage and was almost certainly an early Neanderthal tooth, the first ever found in Britain. But sadly it is now lost. Occasional small excavations continued at Pontnewydd until 1940, when the cave was turned into a wartime store for land mines and depth charges, with the addition of a concrete guard chamber and a grey wall for camouflage across the entrance.
In 1978 Stephen Aldhouse-Green (then of the National Museum of Wales) began new excavations at Pontnewydd that have revolutionized our view of the cave, its age and importance. They showed that the cave once had a series of occupations by early humans at the entrance, when rivers were flowing nearby, some 50 metres above the present river level. But ice sheets that had subsequently surged up the valley destroyed all trace of these ancient visits outside the cave. Fortunately, however, during these ice advances some of the cave entrance sediments became soggy and oozed down into the cave where they survived, not in their original form, but churned up during relocation. After the deposits had been dumped in the cave, stalagmites grew over them, and these have been dated by the uranium-series method, showing that the oldest sludging must have happened, not in the last cold stage, but over 200,000 years ago. Any fossils or artefacts in the oldest mudflows therefore date from at least that time. Deep-sea records show that Marine Isotope Stage 7 was a warm period that began about 250,000 and ended about 200,000 years ago. However, it was a complex stage with a severe cold phase in the middle, around 230,000 years ago, and this provides clues to the sequence of events at Pontnewydd. The human occupation probably dates from an early part of MIS 7, the cold interruption may have led to the first mudflow event, and the stalagmites (which require warm and moist conditions to grow) probably formed with the return of interglacial conditions.
The sequence of fossil mammal bones in the mudflows suggests that human occupation occurred during relatively open conditions. Beaver, wood mouse and roe deer are represented, perhaps suggesting open woodland, followed by species such as lemmings, suggesting cooler, more open steppes. Much later still, long after the phase of human occupation, reindeer, musk ox and wolves roamed a treeless tundra. The mudflows contain hundreds of artefacts, and some are fresh enough to suggest that they have not been transported far. They include more than fifty relatively small pointed handaxes, Prepared Cores and flakes struck from them, and smaller tools that could have been used for working skins or wood, or as knives or spear points. The ancient inhabitants of Pontnewydd faced serious problems in their toolmaking, as there was no primary source of material like flint within 50 miles of the cave. They therefore had to rely on the rocks and pebbles that they could find locally, transported by rivers or by earlier ice flows, and the dominant stones were hard and volcanic in origin. This may explain why some of the tools look quite crude, and why the toolmakers seem to have made some knapping mistakes. Modern replication experiments show that such rocks are certainly more difficult to shape than flint, although reasonable results can be achieved with care and attention. Some of the tools show signs of having been heated, presumably as they lay in or near an ancient hearth, and this has allowed the heating event to be dated by the luminescence method to about 225,000 years ago, consistent with the age obtained from the overlying stalagmite. This dating method depends on measuring the amount of radiation damage that accumulates in an object when it is buried. The high temperature of a fire purges any previous radiation signal, allowing the time since the burning event to be estimated.
Amongst the bones and stones in the mudflows at Pontnewydd were seventeen human teeth, which I have been studying with Tim Compton, a colleague at the Natural History Museum. The teeth are from at least five people, and it seems likely that the tooth lost after 1874 and mentioned above was part of this series. They were probably more complete fossils before they were churned up, but only two of the teeth are now in their original sockets. Judging by tooth wear, three of the individuals were children aged around 12, one was a young adult, and the last was a mature adult. Many of the molars had lost their roots, but where they are preserved, several show a condition called taurodontism, where the roots merge for much of their length. This unusual shape is found in some modern humans, but in fossils it is really known only in Neanderthals, where about 50 per cent of their molar teeth show it. Its origin seems to be genetic and it may confer some advantages where teeth suffer heavy wear. A normal molar will cease to function as a chewing surface when the crown has worn down to root level and it disintegrates. However, in a taurodont tooth, the roots can fill with secondary dentine and remain functional for longer, as the disintegration is delayed. There are also features on the Pontnewydd tooth crowns, such as crests and cusps, that are reminiscent of Neanderthals, and their size and shape is similar to the samples from the Pit of Bones at Atapuerca, dated to about 400,000 years, and to Neanderthal teeth from the Croatian site of Krapina, dated to about 130,000 years. Overall they fit a European pattern of gradual ‘neanderthalization’ between about 400,000 and 150,000 years ago.
Given the redeposited nature of the Pontnewydd finds, it is difficult to reconstruct much more about the human occupation. Certainly the location was a good one, close to a river and raw materials in the form of cobbles and pebbles, and a wonderful vantage point from which to look for game in the valley. The cave entrance 250,000 years ago was probably not large, so it is likely that it provided shelter for only a small group of hunter-gatherers, although we do not know how many occupations are represented in the tools and human fossils. From the tools, it was more than just a sleeping place, with evidence for manufacture, resharpening, butchery and perhaps the working of skins and wood, as well as (by the implication of burnt tools) fireplaces. We have no clues about how these early Neanderthals died and became fossilized, or whether their bodies were left by the occupants or worked over by scavengers. Sites like Krapina show cut marks on the human bones sugges
tive (to some) of ancient cannibalism, but no evidence of this survives on the Pontnewydd fossils. But Pontnewydd is the most north-westerly handaxe site in the Lower Palaeolithic world, and its very remoteness and uniqueness tell us something very important. The lucky escape of the Pontnewydd evidence from the glaciers shows us what we must be missing on the uplands and valleys of western Britain due to the destructive effects of the ice ages.
In contrast, the southern lowlands of the Lower Thames Valley escaped glaciation completely, and two sites in Essex, West Thurrock and Aveley, have yielded important material from the time of Marine Isotope Stage 7, between about 200,000 and 250,000 years ago. An old tramway cutting at West Thurrock has been producing Middle Palaeolithic tools of Prepared Core type for over a century, as well as many shells and bones, while a quarry at Aveley became famous in the 1960s for its elephant and mammoth skeletons, now on show at the Natural History Museum in London. The sequence of river deposits of sands, gravels and muds is similar to the one already described at Purfleet, laid down by the Thames in the previous interglacial, 100,000 years earlier. However, the evidence from Aveley shows clear signs of a disturbance in the middle of the sequence that probably reflects the severe cold stage that interrupted the later interglacial. The earliest deposits at both West Thurrock and Aveley were laid down at the end of glacial stage MIS 8, about 250,000 years ago, but warm conditions soon followed, with woodlands and large mammals such as brown bear, rhinos and aurochs (extinct wild ox). Smaller mammals such as wood mouse, pygmy shrew, bank vole, common vole, water vole and beaver suggest rich vegetation, with rivers and ponds, as do the remains of shellfish and fish. The latter include tench, which require mean summer water temperatures not lower than 20°C to spawn, and this is backed up by the presence of the European pond terrapin, which also needs warm waters to breed. The fish and shellfish together suggest stagnant or slowly flowing water with plenty of vegetation cover, typical of ponds, river backwaters or the lower reaches of a large river.