Devensian Glaciation

The Devensian Glaciation was the most recent glacial period. It started approximately 73,000BP and ended 10,000BP. In the early Devensian ice spread down into the Cheshire Plain from the northwest. It also spread down the East Coast, impeded drainage and creating Lake Humber and Lake Fenland. It has been argued that there was no glaciation in Wales in the early Devensian. Following a number of interstadials the ice sheets reached their maximum extent between 25,000BP and 15,000BP. At that time Holt and Little Witley were on the southern limit of the ice sheet which was centered on the Irish Sea and joined with that from Scotland and thence the North Sea.

Cool summers, averaging 10° C in July and severe winters typified The Devensian climate. The pine and birch forest of the late Ipswichian gave way to herbaceous plants characteristic of periglacial conditions in southern Britain i.e. seasonally snow-free conditions in zone extending approximately 200km from ice front; characterised by tundra conditions & intense frost action. Several sites shed light on the conditions of the Early Devensian, about 70,000 - 50,000BP.

The mixed assemblage of plants recovered from a site dating to 70,000BP, indicate a variety of habitats that suggest braided streams and permafrost. There is evidence that shallow pools on the terrace surface became saline through intense evaporation under the cold dry climate. Strata in Victoria Cave, near Settle in Yorkshire date from approximately this time and contain remains of Reindeer and Wolverine (Gulo gulo), typical tundra species. The presence of these species, plus Steppe Bison (Bison priscus), Wolf (Canis lupus), Brown Bear (Ursus arctos), Red Fox (Vulpes vulpes), Arctic Fox, Mountain Hare and Northern Vole (Microtus oeconomus) from slightly older cave deposits elsewhere in England further point to a tundra like landscape.

Victoria Cave, Yorkshire

The type-site for the Chelford Interstadial dated at 65,000-59,000BP is in Cheshire. Fossil ice wedges and glacial till are exposed in a sandpit at Chelford. The sands originated as a permafrost alluvial fan emanating from the Pennines. In these sands there is a stratum containing peat and macrofossils, needles, cones, and even tree stumps and trunks. The main plant species are birch, pine and spruce and the forest type indicated is thought to be similar to that growing in northern Finland today under a cool continental climate with a mean annual temperature of about 2°C. The arctic-alpine nature of the snail, beetle and pollen assemblage corroborate this conclusion and indicate a continental climate with long, dry cold winters with a February average of -11°C and an average July temperature of less about 15°C.

At Mundford in Norfolk evidence of 60,000 years old butchery by Neanderthals has been found in the form of the in-situ remains of at least nine Mammoths and associated Mousterian stone tools. The worked flint artefacts consisted of number of handaxes, three cores and a number of retouched, utilised and waste flakes. A number of the handaxes and flakes were found in direct association with bones and/or tusks. In addition to Mammoths; Woolly Rhinoceros (Coelodonta antiquitatis), Reindeer (Rangifer tarandus), Horse (Equus ferus), Steppe Bison, Wolf (Canis lupus), Red (Vulpes vulpes) or Arctic Fox and Brown Bear were recorded. Faeces of scavengers (possibly the Spotted Hyaena (Crocuta crocuta) were also recovered. Fractures characteristic of marrow extraction by hominids were identified on the some of the Reindeer and Horse bones. 150 species of insect have been identified. These indicate the presence of standing water, marsh, bare sand and grass. Dung and carcass beetles add to the picture of giant rotting mammals being scavenged by Hyaenas and Neanderthals. The presence of sub-Arctic plants, insects and snails at this site indicates that the Neanderthals of this time lived in a climate like that of modern Scandinavia.

Source: Sedwick C PLoS Biology Vol. 6, No. 4, e99

A typical Devensian scene

The butchering and disarticulation of a Reindeer's back leg using stone tools created cut marks on a bone from Creswell Crags dating from 60,000-42,000 years old. This suggests that Neanderthal (Homo neanderthalensis) hunters were responsible for catching and butchering this animal.

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Neanderthal tools

The type locality for the undated 'Brimpton interstadial' is situated on the River Kennet, a tributary of the Thames. This period is a temperate interlude between the Chelford & Upton Warren interstadials. Animals of this, or a similar interstadial include Bison, Brown Bear, Woolly Rhinoceros, Spotted Hyaena (Crocuta crocuta), Lion (Panthera leo), Wolf, Red Fox, Mammoth, Giant Deer (Megaloceros giganteus), Reindeer, Horse Red-cheeked Suslik (Spermophilus major), Polecat (Mustela putorius) and Stoat (M. erminea).

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..........................................................................Woolly Rhinoceros skull and horns.......................................................................Woolly Rhinoceros Teeth.

The Upton Warren interstadial, named after Upton Warren near Droitwich, was a period of ameliorated climate that occurred in the mid-Devensian, approximate 42,000 - 38,000BP. At that time, the summer temperature is thought to have been about 16°C, i.e. not much cooler than present. The vegetation was largely herbaceous, with a rich variety of species of different phytogeographical and habitat affinities. As the main plant indicators of an interstadial, i.e. birch or pine/spruce are absent; some authors doubt the validity of the description of an ameliorated climate at this time.

The open habitat may however be ascribed to a very high grazing intensity by a large herbivorous mammalian fauna consisting of Woolly Mammoth, Woolly Rhinoceros, Reindeer and, in particular, Bison. It is also possible that other strongly adverse features existed such as very cold winters (January -15°C), severe wind exposure, severe spring thaw and flooding, and. highly unstable soils that liken the environment in the mid-Devensian to that of Siberian river floodplains. The flora was akin to that of present-day south Sweden except for a great scarcity of trees. During this period Wooly Mammoth, Wooly Rhinoceros and Horse occupied Fladbury, near Pershore.

A piece of jawbone, with three teeth, from Kents Cavern, Torquay, dates to between 40,000 and 37,000BP. The specimen was originally thought to be slightly younger and representing a very early record of modern humans (Homo sapiens), however it is now thought to represent the only British example of Neanderthal skeletal remains so ar discovered.

Fragment of Neanderthal jaw

A ridge-top site in Leicestershire, dated to 30,000BP, has produced flint spear points, produced by Neanderthals along with numerous animal bones and droppings suggest the Neanderthals hunted in a land where animals such as the Woolly Rhinoceros, normally associated with cold areas, coexisted with Spotted Hyaenas, only found in Africa today. At this time the Saber-toothed Cat (Homotherium latidens) also probably occurred in Britain.

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...........................................................................................Hyaena skull.................................................................................Woolly Rhinoceros bones gnawed by Hyaenas

Following the interstadial cold conditions returned so that at 27,650BP Woolly Mammoth, Woolly Rhinoceros, Horse, Reindeer, Bison and Musk Ox moved through the arctic tundra at Beckford, near Pershore. The polar desert was colder and more continental than period before the Upton Warren Interstadial. In addition to the species noted at Fladbury, Arctic Lemming, Brown Bear, Arctic Fox and Spotted Hyaena roamed the landscape. The presence of certain beetles indicates 13°C summer and -17°C winter temperatures, and at some sites less than 10°C summer and -20°C winter temperatures. The habitat consisted of tundra with scattered juniper and dwarf birch in the periglacial areas in southern and midland Britain. During the period of glacial maximum Britain would probably have been too cold to occupy by humans.

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.................................................European Bison (or Wisent)....................................................................................................Musk Ox

At its maximum extent ice from Scotland and the Lake District flowed into the Irish Sea and south into Cheshire Plain and Shropshire. The ice was up to 1800m thick. During this advance, the British and Irish Ice Sheet and Scandinavian Ice Sheet were in contact and all of Ireland was glaciated. Due to the amount of water locked up in the ice sheets, the sea level dropped exposing large areas of the North Sea floor, which became deltas for braided channels of rivers draining Europe. The lead into the Last Glacial Maximum is characterized by a sea-level fall of about 50m occurring within a few thousand years.

The Devensian Glaciation ended gradually and unevenly as the climate ameliorated over a period of several thousand years. The 'Windermere Interstadial' thus started around 15,000BP. It was to lasted until around 12,000BP. By 14,500BP the ice-sheet was in retreat and had possibly vanished altogether in west England and Wales. Mammoth remains recovered from a kettle hole in Condover, Cheshire, date to this period (14,000BP). The bones at Condover were associated with interstadial pollen & insect assemblages. By 13,000BP the ice-sheet had disappeared completely from England, Wales and Ireland, and most of Scotland was ice-free. There may however have been residual ice in Scottish highlands through this period. Sea-level rose by rates of up to 15 mm/year during this period.

Some of the Condover Mammoth remains

By 12,500BP summers were at least as warm as today with 17°C mean July temperature and a winter mean of 0-1°C, i.e. a more continental climate than at present. In southern Britain open-ground plant communities gave way to scrub tundra with juniper and willow that gave way to birch-pine woodland. In some regions the formation of the forest was delayed by over 800 years due possibly to grazing pressure from Irish Elk and Reindeer. Red Deer, Moose, Aurochs and Horse also occurred during the Interstadial.

Saiga remains from Gough's Cave, Cheddar, along with those of Horse, Red Deer, Aurochs and Mountain Hare, show evidence of butchery at the hand of man. A number of other cold adapted species also occurred in the Gough's Cave deposits, including Brown Bear, Lynx (Lynx lynx), horse, are, Collared Lemming (Dicrostonyx torquatus), Norway Lemming (Lemmus lemmus), Northern Vole, Narrow Skulled Vole (Microtus gregalis), Wolf, Red Fox, Arctic Fox and rarely Woolly Mammoth. All of the aforementioned animal species are likely to have occurred in Holt and Little Witley at various times during the Devensian.

Some notable species put it their final British appearances during the Windermere Interstadial. Saiga disappeared about 12,100BP and Woolly Mammoth soon afterwards. Some of the most recent Mammoth remains found in Western Europe in Gough's Cave (12,170BP) and Kent's Cavern in Devon (?11,650BP), date to this period. The dated Mammoth tusk fragments from Cough's Cave and Kent's Cavern had both been worked by man.

The first Upper Palaeolithic (Old Stone Age) hunter-gatherer people to return to Britain during the Windermere Interstadial were modern humans. By that time modern humans, who had evolved in Africa, had totally replaced Neaderthals throughout the latter's range in Europe. The last known Neaderthals lived in southern Spain and Portugal 28,000 years ago. A fossil of a 24,500-year-old early modern human child unearthed in Portugal shows distinctive Neanderthal characteristics, possibly the result of interbreeding. After that, all evidence of Neaderthals vanishes including any contrubution to the genetic make-up of modern Europeans.

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Late Upper Palaeolithic tools

The earliest human remains from Gough's Cave date from 14,700BP, just before the onset of the Windermere Interstadial proper. Many of the remains bear a pattern of cut marks compatible with cannibalism.

Skulls from Gough's Cave showing cut marks

In the UK, early humans made distinctive stone tools, including those known as Creswell Points and Cheddar Points. Most artifacts belonging to the ‘Creswellian’ tradition have been found in the Peak District, South Wales and Southwest England. Blades which have been shaped to this trapezoidal outline are known as Cheddar points after Gough's cave in Cheddar Gorge, Somerset, where a large number have been excavated. Patterns of damage on these artefacts suggest that, although referred to as points, they were in fact used as knives. The people who used these tools were highly mobile, as can be seen in Southwest England, where the source of flint was in the upper Thames Valley, but the flints themselves were lost up to a hundred kilometres away. At a date as early as this, trading contacts seem unlikely and it is more probable that people collected the flint themselves and then discarded the tools elsewhere.

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.........................................................................Creswell Crags..............................................................................................A Creswell Point ..............................AA Cheddar Point

Discoveries of cave art in the UK have opened a window in to the world of Palaeolithic man in the closing millennia of the Devensian. At Church Hole in Creswell Crags, examples of cave art of very similar style to that found on the Continent probably attest to links between people of Britain and the Continent at a time when the two land-masses were still joined by a land-bridge. These images include a Red Deer stag, a Bison and a long-necked bird, probably a Curlew. Inscribed geometric patterns have been found in Long Hole and the possible outline of a Mammoth in Gough's Cave, both in Cheddar Gorge.

Red Deer stag in Church Hole

Possible Mammoth carving in Gough's Cave

At Creswell Grags examples of 'portalble art' have also been found, these include an exquisite rendition of a horse etched on to a 7cm long fragment of rib bone.

Etching of a Horse on a rib bone

The size of a Palaeolithic hunter-gatherer group is difficult to judge, but 25 is regarded as a minimum breeding population for human groups. The economy was based on hunting animals and gathering wild plant foods. Evidence for the consumption of plant foods is almost non-existent. Ethnographic parallels with modern hunter-gatherer communities have been taken to show that the colder the climate, the greater the reliance on meat. There are sound biological and economic reasons for this, not least in the ready availability of large amounts of fat in arctic mammals. From this, it has been deduced that the humans of the glacial periods were primarily hunters, while plant foods were more important during the interglacials. By the late Upper Palaeolithic, the dominant food animals included Reindeer, Red Deer, Irish Elk and Aurochs.

The climate warmed rapidly, and was marked by a gradual colonisation of southeastern Britain by scattered birch woodland. This compares with insect evidence, which shows that average summer temperatures right at the start of this phase were at least as high as in the post-glacial period.

From about 12,500BP onwards there was step-wise climate deterioration. There was a final sudden and savagely cold spell (the Younger Dryas period = Loch Lomond Ice Advance) which started 11,000BP and lasted for 500 years, during which forest-tundra vegetation grew in an arctic climate with summer a temperature of 9°C. This period was cold enough for small glaciers re-formed in the high valleys of the Welsh mountains, Ireland & northern England (e.g. the Lake District). 200 independent ice bodies developed in Scottish Highlands & islands, the largest of which were 200km² in extent and 400m thick. Summer temperatures were typically only 8°C in the Lake District, 7°C in the Grampians and 6°C on Skye, and only 1-2°C at sea level. Tundra and low alpine scrub rapidly replaced the woodland and heathland plant communities throughout Britain. Ptarmigan, Arctic Lemming, Northern Vole and Reindeer returned to Britain, but Cave Bear, Woolly Rhinoceros and Woolly Mammoth, did not.

Both Neanderthal and later Cro-Magnon man seem to have actively sought out and destroyed Cave Bears. Brown Bears were also hunted, but these creatures seem to have been less feared by prehistoric man. Cave Bear remains have been found in Suffolk, along with bones of other game animals and predators. In several European cave sites Cave Bear skulls had been neatly stacked or arranged by human hands. The last Cave Bear was possibly killed about 10,000 years ago high in the mountains of Yugoslavia. Cave Bears are estimated to have weighed near to 500kg, for males, while the females were much smaller. A typical Cave Bear skull was about 50cm long, twice the size of a Brown Bear’s skull. Alternate theories exist, but the extinction of the Cave Bear seems to be directly tied to the appearance of modern man as the replacement for Neanderthals in Europe. Furthermore, the Cave Bear was not the only species to disappear at the end of the last ice age.

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..........................................Photo: after National museum of prehistory, Les Eyzies-de-Tayac-Sireuil, France

...........................................................................................Cave Bear ...........................................................................................Cave Bear skeleton

Along with Cave Bears; Cave Lions, Woolly Mammoths, Woolly Rhinoceros, Steppe Bison, Irish Elk and others all vanished. This phenomenon occurred worldwide and all the animals were either large game animals or dangerous predators. Climate change probably was not the only factor causing the crash of populations of megafauna , but the effects of increased temperatures and precipitation will have been an important factor in thier collapse at the Pleistocene/Holocene boundary. The climate change at the start of the Holocene was a major factor in vegetation change, but the climatic effect was amplified as a consequence of the reduced population density of large herbivores. Undoubtedly the 'Mammoth fauna' underwent strong pressure from Upper Paleolithic Man, whose hunting activity could have played the main role in decreasing the numbers of Mammoths and other representatives of the megafauna. Archaeological data testify that the typical representatives of the Mammoth fauna were hunted only until the end of the Pleistocene; their remains are usually not found in the settlements of Mesolithic Man.

Traditionally the last Woolly Mammoths lived in Siberia (with a specimen dated to 9,920 ± 60 BP), however recent dating evidence from remains found in central Estonia gave an age of about 10,000 BP, suggesting a late relict mammoth population living in northeast Europe during the Late Pleistocene/Early Holocene transition. A dwarf form of the Mammoth existed until 3700 years BP, well in to the Holocene, on Wrangel Island, off northern Siberia.

The later part of Younger Dryas (i.e. 10,500-10,000BP) was markedly coldest and most arid, however the glaciers had probably disappeared from Britain and Ireland by 10,000BP.