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Pleistocene Gibraltar

 

The following article has been extracted from the 1999 book ‘Gibraltar at the end of the Millennium: A Portrait of a Changing Land’ by Clive and Geraldine Finlayson.

 

One of the earliest named British batteries in Gibraltar was Forbes’ Battery at the extreme northern end of the Northern Defences, overlooking the north-western corner of the isthmus. It was named early in the 18th century after Lord Forbes, third Earl of Granard, who had been aide-de-camp to the Prince George Hesse of Darmstadt when he landed on Gibraltar in 1704. He was later to briefly participate in the defence of Gibraltar during the 1727 siege but before that he had arrived on the Rock in 1726 when he designed and, with his men, constructed the battery which was to carry his name. The interesting feature of this two-cannon battery was that the guns pointed towards the Grand Battery and not to the isthmus. In other words, should the enemy penetrate that far they would be fired upon from behind. After the 1727 siege the Spaniards admitted that this battery had been the one they had feared most. A barrier which was placed to control the entrance to the garrison between the base of the Rock, below Forbes’ Battery, and the marshy ground and coast to the west was naturally given the name Forbes’ Barrier. During the early and middle of the 19th century significant quarrying took place in this area as described by Edward Kelaart, botanist and medical officer of the garrison, who arrived in Gibraltar in 1843 and published his Botany & Topography of Gibraltar in 1856.

 

A significant amount of scarping had been undertaken in this area by the British in the early 18th century to prevent infiltration by Spanish troops. A case in point was a cavern below Willis’s Battery, sealed after an attempt by Spaniards to mine it in 1727. This sealed cavern can be seen today from Forbes’ Quarry but it is totally inaccessible, the slope leading to it having been removed in the 18th century. The Reverend John White arrived in Gibraltar as military chaplain in 1756 and remained on the Rock for 16 years.

 

Captain Edmund Flint, secretary of the Gibraltar Museum Society which had formerly been the Gibraltar Scientific Society and a contemporary of Kelaart’s, presented to this society a skull on the 3rd March 1848 which had been found in Forbes’s Quarry. This quarry, named after the battery directly above it, had produced the skull of a Neanderthal but its significance was not realised until a long time after and the German specimen, found in 1856, gave this species its scientific name. The 19th century quarrying removed much of the vegetated slope at the base of the cavern. The cave, in which the Neanderthal skull and probably many other interesting remains had been deposited, was almost totally destroyed leaving very little evidence for us to study.

 

After a speculative attempt in 1989 and 1991 a more formal process of research and excavation of Gibraltar’s caves was commenced in 1994 and these investigations into our prehistory have continued annually to today. The 1994 excavation was, curiously, not in the well-known site at Gorham’s Cave where results could be guaranteed but at an untried and relatively unknown and unnamed site at the top of the old watercatchments on the Great Gibraltar Sand Dune. Many years earlier a sand collection operation had been set up on the East Side of the Rock. The sand that was beneath the watercatchments was extracted and transported along a conveyor belt system to the road below and from there taken for industrial use.

In 1985, when the workers had started to remove the sand from the top of this mound they discovered, what appeared to be the entrance to a small cave. They recovered stone artefacts and bones until they were ordered to stop by Mr George Palao of the Public Works Department. He collected these items and arranged for the cave to be sealed according to his notes found years later in a museum vault. When Prof Clive Finlayson took over the direction of the Gibraltar Museum in 1991 he discovered a plastic carrier bag in one of the vaults. In it were stone tools made mainly of red jasper and many mammal bones including an almost complete skull of an Ibex, a wild mountain goat. In the bag was Mr Palao’s report so we were able to establish where the finds came from. We investigated the matter further because it was clear to us that the stone artefacts were of Mousterian tradition. An expedition to this cave was arranged the following year where prehistoric stone tools and more bones were found on the surface shortly after arriving at the site. The cave was yet unnamed but would soon receive the name of Ibex Cave after finding the complete skull of an Ibex (wild mountain goat) there. A formal excavation was carried out at Ibex Cave began in 1994.

 

The combined results of the 1994 Ibex Cave excavation and the subsequent years in Gorham’s and Vanguard Caves are sufficiently detailed now to allow for reconstructions of the environmental conditions around Gibraltar in the late Pleistocene. Gorham’s and Vanguard Caves, like Ibex, are situated on the east side of the Rock but they differ from Ibex in that they are presently at sea level. However, this has not always been the case. Gorham’s had a tradition in prehistory. Captain Arthur Gorham had discovered this cave in 1907, although the sea caverns within one of which lies the cave were known to the 18th century naturalists and historians. In his 1771 History of the Herculean Straits James, for example, describes these caverns filled with wild pigeons and bats which is an account of his time in Gibraltar between 1749 and 1755. It was only in the 1940s that a Captain Alexander discovered ceramic and other artefacts here and conducted a kind of excavation. He did so, apparently, without permission and left Gibraltar without trace and taking the artefacts with him much to the annoyance of the museum committee of the day. As a result the Governor of Gibraltar, Sir Kenneth Anderson, initiated correspondence with the United Kingdom Government to commence a properly-run excavation. It is to his credit that he had the vision to recognise the need to have professionals in such matters. The Gibraltar authorities wanted Dorothy Garrod to excavate the cave and she would have been an ideal person. She had excavated the Devil’s Tower Rock Shelter in the 1920s and had discovered a Neanderthal child’s skull there in 1926. Garrod could not take on the work, however, but she suggested John d’Arcy Waechter of the Institute of Archaeology who was working in Turkey. Waechter came to Gibraltar and excavated Gorham’s, with Spanish labourers, in the course of the 1950s. Despite the crude methods which he employed and the huge volume of sediment which he extracted Waechter was unsuccessful in completely destroying the cave so that when the Museum team returned there in 1989 both Chris Stringer and Andy Currant of the Natural History Museum in London were amazed at the potential which the cave still had. Perhaps surprisingly, Vanguard Cave, about 100 metres to the north had never been excavated and so was in pristine condition.

 

The evidence which has allowed the Museum to piece together the environments outside these caves comes from a number of disciplines. The Neanderthals and, later on, the Modern Humans who occupied these sites lit fires. The remnants of these fires are still there. By taking samples of charcoal derived from these hearths we have been able to do two things. First, the samples have been radiocarbon dated which gives us a very precise idea of when the particular level was occupied and we have had the structure of the charcoal analysed in other samples which has given us an indication of the plants that were cut and thrown into the hearth. Not only does this tell us when particular plants grew in the vicinity, but also what the nature of the climate was as plants can serve as climate indicators. Radiocarbon dating is a very specialised and expensive technique. However, the method cannot be satisfactorily applied to ages beyond around 40-45 thousand years ago. To go beyond this range other techniques have been applied such as Uranium-Series Dating. His results have revealed that the older levels at Gorham’s go beyond 90 thousand years ago.

 

The second feature that makes these caves so useful is the abundance of animal remains found in many of the levels – mammals, birds, reptiles and amphibians, sometimes fish and many molluscs. Together with the plants these remains have allowed us to reconstruct these prehistoric environments of Gibraltar. Some of these animals were clearly brought back to the caves by humans and a number of these show evidence in the form of cut marks or burning. Others may have been brought in by carnivores which, as we shall see, were abundant in the area. Others would have come of their own accord and died in the cave.

 

Before we can begin to interpret the environments we must understand the nature of global climate change in the last two million years – the Quaternary. The early view of a world which could be divided into four major “Ice Ages” during this period has long been realised to have been over-simplistic. Studies of deep sea cores in the North Atlantic or of the Greenland Ice Core, for example, have helped to show that the climate was much more variable than previously anticipated. At times the mean global temperature may have been even higher than at present though at other times it was significantly lower. The period that concerns us starts around 120 thousand years ago and was warm. It was the last interglacial – a major warm period between two cooler periods. The sea level around our coasts was probably even higher than it is today, perhaps by as much as 8m as ice in the poles melted. A progressive period of cooling started shortly afterwards and culminated in two very cold episodes, one between 90 and 60 thousand years ago and another from 25 to around 13 thousand years ago. The intervening period was highly variable, though often mild, but never as warm as the interglacial. The cooling that took place for much of this period meant that much seawater froze and the sea level, in the western Mediterranean including Gibraltar, descended by up to 130 metres below present levels.

 

What effects did such a lowering of the sea level have on the environments and the inhabitants of the Rock? The Bay of Gibraltar in the west is very deep, over 400 metres in places, as deep as the North Sea. A lowering of the sea level of around 100 metres would have exposed a coastal shelf but not much more. The Bay would have taken the shape of a deep estuary into which the ancestral Palmones and Guadarranque Rivers would have flowed. In the east the situation would have been very different. Here a similar lowering of the sea level exposed a large area of land of up to 45km2. This land was immediately on the doorstep of Gorham’s and Vanguard Caves.

 

Our interpretation of the information which is emerging from these sites is that Gibraltar was sufficiently far south never to have completely lost its Mediterranean vegetation. We have found in levels dated around 40-50 thousand years ago charcoal belonging to warmth-loving plants, true indicators of a Mediterranean climatic régime. Perhaps the most striking of these is the wild Olive but equally significant, though less well known, are the Stone Pine and the Lentisc. So with the exception of the really cold episodes, when the vegetation did change quite radically as we shall see, the Neanderthals lived in Mediterranean-type conditions.

 

So what was the landscape of the Neanderthals like? We can best describe it as a kind of wooded savannah of a Mediterranean kind. The nearest comparable environment today would be the Doñana National Park in south-west Spain. Sand is the crucial element in common with the old Neanderthal environments of Gibraltar. The drop in the sea level caused the exposure of large expanses of sand off the east side of Gibraltar and the vegetation that grew there was similar to that of Doñana. The predominant tree was the Stone Pine. Its umbrella-like structure prevents dense woods forming. The wide crowns keep the trees apart and this allows sufficient light to penetrate to the ground to allow a rich shrub and grass layer. The Gibraltar sand dunes would have exhibited a dynamism similar to those of Doñana today and so there would have been open areas where trees had not had time to grow or where the shifting sand would have engulfed them.

 

In Doñana another tree is common and forms large, open, copses in areas of higher ground. This tree is the Juniper and we have found that a species of juniper was also present in the Gibraltar sand dunes and it was the second commonest tree there too!

 

So the vast expanse of sand dunes of the east side presented a mosaic and ever-changing patchwork of open vegetation, in places rich in grasses, in others with a rich shrub layer of heathers and rock roses, yet in others with scattered trees or even small woods. This environmental mosaic provided for a rich and abundant fauna. Among the herbivores the predominant mammal, as in Doñana today, was the Red Deer. Wild horses and cattle were also present. The Wild Boar rummaged for roots in the undergrowth much as it does today in Doñana. There were also remnants of an ancient fauna, most notably the last of the Narrow-nosed Rhinoceroses that were once widespread across Europe.

 

It is not therefore surprising that such a community of herbivores should attract a rich assemblage of carnivores. Here is where the analogy with the environments of an African Serengeti becomes most appropriate. Among the large scale predators were Lions, Leopards and Spotted Hyaenas. These animals roamed the sandy plains. Some, like the Leopard, would have been at home on the trees. Hyaenas would have found the caves ideal dens, that is when humans were not around. To these predators we must add others which are still found in the area or which have only been eliminated by Man in historical times – Wolf, Lynx, Wild Cat, Brown Bear. This then was the Gibraltarian Doñana of 40 thousand years ago, but there was more…

 

Other Mediterranean plants also grew on the Rock as we noted earlier, especially Olives and Lentiscs. It is unlikely that these grew commonly on the sand dunes and it is more likely that they were collected from the Rock itself where they may have easily grown, just as they still do today. The cliffs of the Rock also added another important faunal component. This was the Ibex, a wild mountain goat, which along with the Red Deer were the main mammals consumed by the Neanderthals. Sites, such as Ibex Cave up on the cliffs, may well have been seasonal places where the Neanderthals went specifically to catch these goats.

 

There is also evidence that a shallow river estuary may have opened into the Mediterranean somewhere in the present-day isthmus. This possibility is supported by the large presence of waterbirds – ducks, geese, etc., found not just in Gorham’s but also, notably, in the Devil’s Tower site which was excavated by Dorothy Garrod in the 1920s. This site would have been very close to this marshy ground. In addition, we found a level in Vanguard Cave which indicated that the Neanderthals had been collecting and eating mussels. It appeared as a singular event, these people having arrived with the mussels and a flint nucleus, made the tools on the spot and cooked the mussels in a fire. The charcoal allowed us to date the event at over 40 thousand years ago! We were able to collect all the waste flakes and reconstruct the original flint pebble.  Evidence from other camp fires in Vanguard and Gorham’s also showed that these people also collected plant matter for food, with roasted pine nuts appearing to be a favourite.

 

If the seasonal régimes functioned in a similar manner to Doñana, with a dry summer season, then it is very likely that these wetlands would have been especially important hunting grounds in the summer when the larger mammals would have come to drink in the receding water pools.

 

The system which we have described in all likelihood predominated for tens of thousands of years.  Sometimes the sea would gain on the dunes, other times the plains would grow. Dry periods would reduce the extent of the wetland areas, and so on. The important point to note is that a Mediterranean régime predominated throughout.

 

When conditions worsened after 35 thousand years ago and Europe was poised on the verge of some of the coldest conditions it was ever to face, the environmental conditions in southern Iberia changed. Inland, the Mediterranean mountain woodlands were replaced by arid steppelands which favoured the expanding populations of Modern Humans. The changes even affected the coastal lowlands and Gibraltar did not escape. It is at this time that we begin to see the entry of mountain vegetation, migrating to lower altitudes in response to the increasing cold. The charcoal in Gorham’s shows a replacement of the lowland pines by species which are characteristic of the mountains. The vegetation in Gibraltar had been open, with wooded and grassy savannahs that attracted many herbivorous mammals, which the Neanderthals had hunted for tens of thousands of years. The effect of this change was that this vegetation was replaced by a dense forest of Black Pines, which severely limited the growth of grasses and shrubs in the under-storey. This would have reduced the carrying capacity of the environment, and the Neanderthals it seems were unable to cope with the sudden change and became extinct. The Modern Humans, on the other hand, had radiated from Africa via the Middle East and had, through a combination of new hunting strategies and cultural adaptations, been able to survive the cold conditions of central Europe for at least twenty thousand years. They were only recently arrived in Iberia, from the north, but their arrival was one which would significantly change the course of the world. By around 30 thousand years ago the Gibraltar of the Neanderthals had gone to be replaced by that of the Moderns who were here to stay…