There is one particularly unusual feature of the large mammals at West Thurrock and Aveley. In Britain, the alternating conditions of glacial and interglacial are normally marked by alternations of certain species, such as reindeer and mammoth in the cold stages, red deer and straight-tusked elephant in the warm ones. However, in this interglacial the straight-tusked form is there as would be expected, but it is joined later by a species of mammoth as well. Moreover, there are many more mammoth fossils than straight-tusked elephant ones in the later deposits at Aveley, and at West Thurrock, so what does this mean? Well, the mammoth in question has small and distinctive molar teeth compared with the normal mammoths we find in the ice ages, and it seems to represent a less specialized form that grazed warmer grasslands rather than cold steppes. After the cold interruption, about 230,000 years ago, the forested vegetation of the Aveley interglacial never fully recovered and the dominance of grasslands seems to be reflected not only in the prevalence of these mammoths but in greater numbers of grazing rhinos and, now, horses. This suggests that new species such as the mammoth and horse migrated into Britain after the cold interruption, implying a physical connection with the rest of Europe at this time. These new species included a unique and exotic record for Britain: the jungle cat, which despite its name is most commonly found in grasslands and marshy ground near rivers in southern Asia today.
The Aveley interglacial is also represented in deposits further up the River Thames at Ilford in Essex, and in other areas such as Suffolk (Brundon and Stoke Tunnel), Buckinghamshire (Mars-worth) and Oxfordshire (Stanton Harcourt). At this last site, in quarry deposits that may have been laid down in the upper reaches of the ancient Thames, about a thousand large bones, teeth and tusks have been recovered including those of bison, bear, lion, horse, hyaena, and once again, elephant and mammoth. Fifty species of shellfish and snails, ninety species of insect, and well-preserved remains of pollen, wood, nuts and seeds from oak, hornbeam, alder, hazel and willow paint a vivid picture of the environment there about 200,000 years ago. Grasslands, grazed by bison, horse and mammoth, bordered the river but there were also forested areas nearby, frequented by deer and elephants. A few stone tools give witness that humans were also there, at least occasionally. The Aveley interglacial inevitably drew to a close, and a site south of the River Thames at Crayford in Kent shows the transition into the long and severe cold stage of MIS 6. Crayford signals the oncoming glacial with the appearance of large mammals such as woolly rhino and musk ox, and small ones such as lemmings and ground squirrels. Humans hung on at Crayford for a while, for there are beautiful flint flakes made by the Prepared Core technique alongside woolly rhino jaws, but Britain was about to enter the longest phase of human absence seen for half a million years – an abandonment lasting over 100,000 years. During this time the nearest evidence of human occupation has to be sought across the Channel, in Jersey. Today the Channel Island resort of Ouaisné has golden sands lapped (on a good day) by a beautiful blue sea. But 150,000 years ago, its sea cliffs towered above a vast cold prairie where woolly mammoth and woolly rhinoceros roamed and early Neanderthals camped and butchered the carcasses of their prey. The nearly treeless prairie stretched towards England and all the way to France. Even a fall of sea level of 20 metres was sufficient to rejoin the Channel Islands to France, and at times of maximum glaciation the fall exceeded 100 metres.
Excavations at a deep rift in the cliffs called La Cotte de St Brelade began in 1910, and culminated in major excavations during the 1970s, in which Prince Charles took part when a student at Cambridge. The digs have produced extensive evidence of early human occupation spanning a quarter of a million years, some 140,000 stone tools, and intriguing piles of mammoth and rhino bones dating from about 150,000 years ago. On at least two occasions, separated by thousands of years, it seems that the early Neanderthals at La Cotte drove herds of mammoth, accompanied by a few woolly rhinos, over the cliffs or into the chasm to their deaths. We do not know how they did this, but extensive evidence of burning in the site raises the possibility that fire was involved, either the firing of dry vegetation or the use of torches. Nevertheless, stampeding the herds in this fashion would have required planning and teamwork, as well as bravery.
The Neanderthals must have dismembered the carcasses into chunks that they could carry or drag into the shelter of La Cotte, and bones, skulls and tusks were probably piled up against the walls of the chasm as they finished working on them, or to keep access and floor-space free. Whereas they normally returned to the site repeatedly, on these two occasions people did not come back for some time, and dust storms blanketed the bone heaps, protecting them for the next 150,000 years.
The stone tools found at La Cotte vary from small flake tools early on, through assemblages dominated by scraper tools (for working skins?), to the kinds of tools made by late Neanderthals in neighbouring Brittany. Microscopic study of the flake and scraper surfaces shows that some have what looks like hide polish, while notched tools occur in different frequencies, which may reflect the differing availability of trees in the surrounding landscape. The frequency of possible spear points also generally increases through time, with particularly sturdy examples being manufactured in some of the levels with bones of megafauna such as mammoth and rhino, perhaps an indication of a requirement for strength. Whereas the first inhabitants of La Cotte seem to have had abundant supplies of flint, tools in the later levels show much greater evidence of reworking and rejuvenation, suggesting that raw material was becoming scarcer. An interesting by-product of archaeological study of the direction of the resharpening processes is a demonstration that it was predominantly carried out by right-handers in a ratio of 4:1, close to the normal ratio of right- to left-handers in people today.
As already mentioned, there is extensive evidence of burning throughout the deposits of La Cotte, in the form of burnt tools and stones, charcoal, bone fragments and comminuted bone powder. Its presence seems to correlate with the presence of stone tools and butchered bones, suggesting that it is directly associated with human activity, rather than the result of natural fires, and as such is one of the earliest good examples of this behaviour in Europe. However, no hearths were preserved in the lower levels, either because fireplaces were unstructured, or because they have been reworked by later activity. But what is especially unusual about the La Cotte evidence is that burnt bone fragments greatly outnumber those of wood, suggesting that in relatively treeless landscapes the Neanderthals resorted to burning bones. This may seem an unlikely practice to us, but people who live in similar environments today, such as the Inuit, regularly burn bones for fuel. Mammoth and rhino bones would have had a high fat content, and would have burnt well once they were at a high temperature, implying that kindling would have been needed to start the process.
So if people (presumably early Neanderthals) were in Jersey 150,000 years ago when the sea level was low enough to connect what are now the Channel Islands to France in one direction, and to southern Britain in the other, why didn’t they regularly cross what is now the bed of the Channel into England, if it was dry land? This brings us to one of the key questions in understanding the ancient human occupation of Britain: when did Britain become an island for the first time? This question is not as straightforward as it might seem, because the creation of Island Britain was not just a matter of the sea level becoming high enough to cut Britain off from continental Europe. As we explained in Chapter 1, there was a high ridge or plateau of chalk rock connecting Kent with the French region of Artois, and until this was cut through, sea level rises on their own were not enough to isolate Britain. So what happened to breach the chalk, and when did it happen?
If we go back to the Pliocene period, over 2.5 million years ago, Britain seems to have been an island then, surrounded by mild seas. Although the Antarctic continent had been ice- and snow-bound for millions of years, there was little ice at the North Pole and in Greenland, and so sea levels globally were much higher than today. But aroun
d 2.5 million years ago, changes in the Earth’s oceanic and atmospheric circulation patterns started a permanent build-up of ice and snow in the north, which led to a sea level fall, and the gradual exposure of a plateau of land around the chalk ridge between Britain and continental Europe. In addition, European rivers flowing into the region of the present North Sea extended their headwaters and dropped increasing amounts of sediment into the southern North Sea basin, gradually increasing the area of land connection so that Britain was a peninsula of Europe by about 1.8 million years ago. This was still the situation when massive ice sheets started to spread across northern Britain in the glacial stages after 700,000 years ago. Geological evidence shows that a huge freshwater lake built up in what is now the southern North Sea towards the end of the severe Anglian glacial stage, corresponding to Marine Isotope Stage 12 (about 450,000 years ago). The chalk ridge formed the southern shore, but eventually the lake overflowed and cut through the chalk to form the Strait of Dover. Other workers, however, have suggested that the event was much later, and that the Strait was still closed during MIS 7, 200,000 years ago. In which case the Channel could have been cut during the succeeding cold stage.
A team of researchers at Imperial College, led by Sanjeev Gupta, has been using the results of advanced sonar investigations to survey the sea floor several miles off the Sussex coast, in order to study how the Channel formed. A special echo sounder, strapped to the hull of a survey boat, has revealed a landscape hidden beneath the waters for ten thousand years. During the low sea levels of the glacial stages the River Arun, which now enters the Channel at Littlehampton, ran on for several miles before flowing into a valley carved by a massive south-flowing river created by the combined waters of the Thames, Rhine and Seine. In places this huge underwater valley is more than 10 kilometres (7 miles) wide and 50 metres deep, with vertical sides, and its nearest geological parallels are found not on Earth, but in the monumental flood terrains of the planet Mars. This suggests that the valley was not formed by normal geological processes, but was indeed created by catastrophic flood flows following the breaching of the Dover Strait, and the sudden release of water from a huge ice-dammed lake to the north. Gupta believes that the creation of the English Channel was one of the most powerful flood events known on Earth. However, the timing of the event is still not clear, and it could even have happened in two stages, perhaps even in two separate glacials. Clues to the timing of the breach could come from studying geological cores produced when the Channel Tunnel was being built, and from sampling deposits in and around the huge submerged river system, and this is something Gupta and AHOB are pursuing. But knowledge of the scale of the Channel river also changes our perceptions of Britain’s isolation from the Continent. The old view that the Channel formed a barrier to movement only in interglacials must be modified – even at times of lowered sea level this deep and wide river could still have been a formidable obstacle to the movement of animals and, without boats, humans.
This irreversible alteration in geography might have combined with changing environments to make Britain gradually less suited to human occupation. It probably took a long time for humans to adapt properly to European environments, and to make things worse the environments themselves gradually transformed through time as climates became more extreme. The Neanderthals in north-west Europe increasingly adapted to cooler and more open environments and this is reflected in a reversal of the earlier situation, where it was the interglacials that showed the densest occupation. For example, the remains of mammoth, reindeer and horse dominate German Middle Palaeolithic sites, and in the briefer warm stages the Neanderthals seem to have preferred to migrate eastwards to the more open steppes. The distribution and movement of herds in the steppes would have required greater human mobility and more portable technology, which is perhaps why the Prepared Core technique became more common, and people left less stone tool debris behind. If Britain had less of the preferred steppe environments, particularly in later interglacials, then the Neanderthals may have had a hard time surviving there, particularly if their mobility was restricted by the growth of a massive Channel river system in the colder periods, and the Channel itself in the interglacials.
There are clues in biology and archaeology indicating when the breach between Britain and continental Europe occurred, and to its scale. By looking at the warmest stages of the interglacials, when ice caps should have been at their smallest and sea levels at their highest, we can see that there are greater similarities between these neighbouring regions in both mammals and molluscs (land and water-living) during the warm stage 400,000 years ago than the warm stage 125,000 years ago, suggesting the breach was either absent, or less significant, during the earlier warm stage. The later warm stage, the last interglacial (if we don’t count the one we are living in today), is known in Britain as the Ipswichian, after the site in Ipswich where its distinctive pollen signal was recognized. Most experts accept that Britain was an island by then because it was home to an idiosyncratic combination of mammals known as the Joint Mitnor Cave Mammal Assemblage-Zone, after a site in Devon. This unique assemblage is found nowhere else at the time. It was first excavated from Kirkdale Cave in Yorkshire in 1821 by William Buckland, and this is one of several sites in the region where hyaenas seem to have been scavenging hippo carcasses at lakes or rivers. At Victoria Cave, 400 metres up on the now craggy Yorkshire Dales, we have one of our best fixes on the age of this odd fauna, since fossil bones are enclosed in stalagmite that has been dated to about 120,000 years ago by the uranium-series method, which relies on the steady decay of radioactive uranium into its daughter products. And Buckland was right in one of his major observations about this ‘hippo fauna’ – there are never any associated human relics (another contrast with the preceding four interglacials, which always have some evidence of humans).
At first glance much of mainland Britain, from Yorkshire southwards, would have looked to us like a wooded African game park with lion, hyaena, hippo, elephant and rhino. But on closer inspection, more familiar species like red deer, fallow deer, water vole, wood mouse and field vole would also have been seen, although horses were absent, unusually for an interglacial. Most of the species present must have been fast movers, for the warm start of this interglacial seems to have been rapid, along with sea level rise, as the previous glacial ice melted. Plants, insects and birds would have been amongst the first colonizers from Europe, followed by herbivorous and then carnivorous mammals. Some large mammal species could even have swum across. We know that hippos were happily wallowing in the Mediterranean at this time, so once the ocean was warm enough they could simply have swum along the Atlantic coasts towards Britain, and then swum up the rivers (including the Thames, where their bones have been excavated from the foundations of buildings on Trafalgar Square). If we assume that hippos in Britain behaved similarly to the living species in Africa, herds of up to thirty of these enormous animals would have wallowed together in shallow rivers or lakes. In the evening they would have emerged to feed separately, and they do feed on an enormous scale, sometimes travelling several miles in a night. A hippo can graze for about six hours and consume up to 100 pounds (45 kilograms) of grass in that time, and so even a single herd could have made quite an impact on the vegetation around British rivers and lakes.
Plants and insects suggest that the climate was at least one degree warmer than today, with mixed oak and hazel forests and some southern exotics such as the Montpellier maple and water chestnut. Bird faunas show the same pattern, with Mediterranean species such as Cory’s shearwater nesting on British coastlines. At this time the subtropical Gulf Stream was flowing northwards particularly strongly for about 15,000 years, and the existence of the Channel would have facilitated the spread of these mild Atlantic waters through the North Sea, towards the Baltic. This may well explain why it was not just Britain that was balmy at this time. Fossil pollen suggests that hazel and alder were growing as far north as Swedish Lapland, and from the evidence of ancien
t shorelines Scandinavia was probably an island too. Ireland must have been similarly sultry, but surprisingly little evidence has so far emerged from there.
About 115,000 years ago, that balmy flow across the Atlantic suddenly switched off as the oceanic conveyor belt that transfers subtropical warmth northwards reversed, and Britain’s climate started an erratic downturn into the last glaciation. Sites that we have excavated in the Gower Peninsula such as Bacon Hole and Minchin Hole caves show this decline about 90,000 years ago, with the disappearance of some warmth-loving species and the appearance of cooler indicators such as mammoth, and northerly birds such as the long-tailed duck and bean goose. Some interglacial species, elephant and narrow-nosed rhino, still hung on in this assemblage, known as the Bacon Hole Mammal Assemblage-Zone. But 15,000 years later they had finally all gone, as evidence from Banwell Bone Cave shows. We encountered this Somerset site in the Introduction, where it figured as a solemn reminder of the Flood, a sort of biblical deluge theme park. And it is easy to see why people in 1825 were so impressed by what they saw. William Beard, a local collector, had found so many fossil bones in the cave that he piled thousands of them in decorative stacks against the walls. The great majority were of bison and reindeer, with rarer species such as wolf and brown bear. The bear remains are often huge, suggesting a powerfully built runner with small teeth, and enormous claws, an active hunter like a polar bear. The wolf skulls and jaws have heavily worn and broken teeth, suggesting that this species might have been filling the role of scavenging and bone crunching normally taken by the hyaena, of which there is no trace at this time. The assemblage of mammals is so distinctive that it can be recognized at a number of other British sites, all of them placed in the Banwell Bone Cave Mammal Assemblage-Zone, and representing a cold stage about 75,000 years ago, with forms like arctic hare, arctic fox and wolverine. As well as hyaena, there is once again another notable absentee from the Banwell mammals: Man. There is not a single fossil human or archaeological relic from this time, continuing the pattern of the previous interglacial.
Homo Britannicus Page 12