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 8 metres 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 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 45 square kilometres. 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.
The Azure-winged Magpie is a colourful bird, unusual for a member of the crow family. Its present geographical distribution is very unusual. You find these birds in south-western and western Iberia, roughly from the Coto Doñana near Seville to areas north of Extremadura and west across much of Portugal. There are no historical records of this species in Gibraltar. The nearest site where you can see them nowadays is, to our knowledge, the pinewood of La Algaida on the southern shore of the Guadalquivir River near the town of Sanlucar de Barrameda. If you want to see this bird outside Iberia you have to travel east, all the way to China or Japan! You do not find them anywhere in between. For many years scientists have been puzzled by this extreme example of a disjunct distribution. Could the extreme cold of a glacial event have separated this bird into two milder refugia without them having met again afterwards? Many thought this unlikely and went for a more plausible option. Azure-winged Magpies are colourful and intelligent birds. They would make good pets. So it must have been the Portuguese navigators of the 16th century who brought them back to Portugal from China and they then escaped and formed feral populations. Neat, but not true!
Once we had established the Gibraltar Caves Research Project and excavated Gorham’s we realised that a massive number of bird bones were being collected from the various levels. Some of the bird material excavated in the 1950s by John Waechter had been studied and published by Anne Eastham in 1968. Her identifications and interpretations were in some cases highly suspect, something that Clive Finlayson had raised as far back as 1980 when he co-authored the book The Birds of Gibraltar. So we needed a new look at the birds. The analysis of the material needed a fresh approach and someone completely dedicated to the task. Jo Cooper had just completed her degree in the Royal Holloway College and she had studied some of the micromammal fauna for her dissertation. We had close links with her department. After all Ted Rose had spent a long time on the Rock researching its geology. Jo had an interest in birds too so she was a natural candidate for the job which she undertook to do as her PhD thesis.
An email from Jo brought great excitement one day. Not many would have reacted like we did but we were fully conscious of the significance of her latest finds. She had discovered the remains of Azure-winged Magpies in Gorham’s and Vanguard Caves in levels associated with Mousterian industry. In other words, these birds were around in Gibraltar at the same time as the Neanderthals, 40 to 50 thousand years ago! They had been here all along and had clearly had a much wider geographical distribution then. Clearly the Portuguese had not brought these birds back in historical times.
This bird’s contribution to our state of knowledge did not end here – far from it. We had been studying the distribution of birds across Iberia, from Portugal in the west to Almería in the east and we were attempting to use birds as indicators of vegetation type. Many species had a wide range of choice and many were migratory so they could not be used with any degree of confidence. The Azure-winged Magpie was very different in this respect. For a start, as a strict resident (in other words it did not migrate) it rarely wandered far from its territory, and its habitat requirements were very specific. Of over 800 sites visited we only found them in 4% of them. So we used the bird to model the vegetation and the model closely matched the results from the charcoal analyses!
So what was the landscape which the Neanderthals and the Magpies shared like? We can best describe it as a kind of wooded savannah of a Mediterranean kind. The nearest comparable environment today would be the Coto Doñana in south-west Spain. That was also convenient because for four wonderful years between 1993 and 1997 we had been privileged to work, with our colleague Mario Mosquera, within the Biological Reserve of Doñana. For each month of those years we would drive for three-and-a-half hours, usually on a Friday after work, from Gibraltar to Doñana. There we would take up residence in the old palace of Doña Ana, wife of the ill-fated Duke of Medina Sidonia of Armada fame. The palace is situated on the edge of the vast marshes – the Marismas del Guadalquivir – and it is now part of the research facilities afforded. We would usually spend the entire Saturday and most of Sunday surveying the vegetation, the birds and the mammals within the reserve before returning, usually late, to Gibraltar in time for work the following day. Sometimes we would stay for longer periods, of up to a week or more, and we developed a deep understanding of how life survives and prospers on sand!
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 Phoenician Juniper. Although we cannot confirm the specific identity 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 thirty thousand years ago the Gibraltar of the Neanderthals had gone to be replaced by that of the Moderns who were here to stay…