Читать книгу Extinction: Evolution and the End of Man - Michael Boulter - Страница 5

Most people have some kind of overview of the history of the last thousand years, but few can see back much further. Tirefour Broch, an Iron-Age fortification, stands on the island of Lismore in western Scotland. Archeologists claim it is about 2,100 years old, a 12-metres-diameter stone circle still standing 3 metres high (see figure 1.1). The broch is on the highest part of the long island and has spectacular views over the waters of Loch Linnhe to Fort William and Ben Nevis in the north and the Isle of Mull in the west. But these views are very different from those seen by the fort’s builders and inhabitants, protecting themselves from brigands attacking from the mainland forests, their sheep and chickens safe from the mainland’s wolves. Then, the mountains and the lowlands down to the sea were covered with dark forests of Scots pine, oak, birch and alder. Above the tree line grew the now widespread purple heather, holly and cranberries, mixed in with small shrubs. The animals that roamed this area were diverse and fierce. It was not a good place for the new humans migrating there from the south and east for the first time. At least the winters were warmer than on mainland Europe. This was due in part to the oceanic climate from the Atlantic Ocean’s Gulf Stream that wound up the west coast of England towards Lismore.

Scottish brochs such as Tirefour were built a few hundred years later than the pharaohs’ pyramids in Egypt when the young Tutankhamun was king, a civilisation much more advanced than Scotland’s. The contrast between this thinly populated island and the sophisticated communities of Egypt along the banks of the Nile is marked. In Scotland it was a hard, cold life with continual threats from other humans reaching the end of their migration trails and from hungry animal species. In northern Africa, the warm open grassland prairie and desert scrub teemed with mammals such as gazelle, ass, hartebecst and hyena.

The sight of these prairies was not far removed from what you still see in nature reserves further south on that continent in Kenya down to South Africa. We know the mammals that roamed further north from paintings found in Tutankhamun’s tomb showing the king hunting in his chariot with courtiers, fan-bearers and bodyguard. It was easy to settle in the river valleys where whole communities had become established and the treasures that survive along the river Nile bear witness to their cultures.

At the same time, far northwards the cold winters made life a lot less comfortable for the migrating humans. By then mammoths and other large mammals had become extinct, killed off by human hunters, after they had taken millions of years adapting to the more extreme conditions. The new humans were trying to acclimatise much more quickly, helped by their intelligence and skills to make spears, daggers, clothes and shelter. The broch on Lismore, and twenty or so others like it on neighbouring islands, is among the oldest buildings in Europe. Although most of them are being broken up by the weather and more recently by vandalism, they are being preserved by slow immersion into the landscape of pasture. Enough evidence survives to allow us to reconstruct much of the way of life of the Iron Age settlers, their hunting, culture, religion, their relationship with the natural environment. Life was hard but becoming ordered, barracked within these communes. Archeologists are also discovering bronze swords and other weapons at contemporary sites along the Atlantic seaboard of western Europe, which suggests that trade and fighting were part of their life too.

Entry to the broch was by a very narrow passage to a central courtyard where meals were prepared, livestock fed, and groups worked together. Around this area, next to the inside of the wall, was a two-storey wooden structure roofed with straw. This was split into small chambers for sleeping and storage. Variations of this kind of structure were built by other early human groups in different continents as man and civilisations migrated. The communal kasbahs in Morocco are still inhabited, with the central courtyard for animals, and the occupants cooking, sleeping and defending in rooms around the sides. In Kazakhstan partitioned tents serve the same purposes for still migrating people. As well as being good defensive fortresses against other human groups and tribes, they also offered protection from animals of prey threatening their livestock.

Men farmed barley and hunted together in teams, women looked after livestock, cooked, and nursed children. There was little privacy for cosy family gatherings. Instead there were large groups, sharing knowledge and experience and using language to plan survival strategies. The change from life within a threatening hostile environment to a secure family routine has been happening in all social groups throughout the world at different times over the last few thousand years. In those days, thousands of years ago, with our urge to plan ahead, we learnt how to protect ourselves from the dangers of the naturally hostile world. We also began to control some of the natural processes, making fire, and using minerals such as tin for bronze. This can be seen as a grand revolution in control of natural resources which led to the beginning of politics and societies. It meant that for the first time a species interfered consciously with the balance of nature, taking things from it, changing it for its own advantage.

Before Tirefour Broch, without human occupation in far north-west Europe, the ecology comprised stable woodland with grassy glades allowing herbs to grow in the sunshine of natural clearings. Within this steady state mammals, birds and other animals were integrated to form a stable balanced ecosystem. There was no waste. As in all natural systems, the ecosystem was built and controlled from within. It had a kind of peace and harmony. Only external forces changed this delicate balance, and in doing so promoted evolution of large different groups within the plant and animal kingdoms of that changed environment.

There are many sources of evidence for such forcing from outside the planet as well as from within its complex structure. From outside there are asteroid and comet impacts, the gravitational pull of other planets and our moon, the effect of sunspots and solar wind. The God-fearing astronomer Fred Hoyle argued that viruses, and therefore life itself, came from outer space. From inside the planet system, there is ecological succession, erosion from the weather, seasonal environmental change, fights between different species and individuals, and of course, selfish genes.

In the British Isles, the building of Tirefour Broch was one of the first changes to the environment brought about by humans. We are the only species that can force big changes on the environment, and over the last 3,000 years we have been doing that with consequences often beyond our understanding and possibly out of our control.

Imagine the other changes since these early days of the family unit, all caused by the increased human population and activity, grazing, urbanisation and tourism, pollution and waste. They had led to deforestation, species becoming extinct, rising sea level and climate change. Such devastation covers most of the landmasses on the planet, while different but just as destructive changes are being inflicted on the oceans. There are few populated parts of the world which have the same landscape now as 3,000 years ago, untouched by human endeavour.

In the British Isles the only place you can stand and see the same view now as then is on the Burren in County Clare, just south of Galway Bay. This is several square kilometres of limestone pavement which has resisted interference because there has been nothing that could be done with it. Clambering across the huge exposed blocks of rock, grikes criss-cross the surface. These ‘dykes’, often more than a metre deep, have their own microclimate which attracts a special flora and fauna. The Burren is remote and has a threatening atmosphere, with nowhere to hide from the strong winds. Clouds blow in fresh from the Atlantic. The grey limestone hillsides sweep down to the sea off Black Head, the Aran islands in the distance, still with a small human population of their own and a history not unlike that of the Scottish islands with their brochs and bronze swords.