Fields of dreams

IT is usually safe to congratulate me on the beauty of Thallabawn, as if I had personally taken a hand in the composition of mountains and sea and arranged the sun just so. But sometimes, in a jaundiced mood, I may lament the long saga of the spoliation of Connacht, beginning with the first Neolithic farmers and coming up to 2000 AD with overgrazing, turf-mining and coniferisation.

This could, it turns out, be a little unfair to the Neolithic settlers - at least to those who set up the Ceide Fields, that incredible web of stone-walled pastures, buried beneath the bogs of north Mayo.

It has always seemed possible, even probable, that the farmers were forced to abandon their land through a deterioration of the soil that created conditions for peat formation. The notion that they actually paved the way for their own demise, by chopping down the trees that had protected the soil from the rain, had a certain appeal to those of us with a dour view of the human record.

But now it's suggested, from new data, that what befell the Ceide people after a mere 500 years had nothing to do with soil or climate and that the causes "are more likely to be found in social and demographic developments within the Neolithic community".

The new insights arise from the latest chapter of pollen investigations by Michael O'Connell and Karen Molloy and their students in the Palaeoenvironmental Research Unit at University College, Galway. By analysing the pollen in cores of peat and sediment extracted from lakes and ancient bogs, they are putting together a detailed history of human impact on the region's vegetation.

The cores at Ceide were taken from a small, peat-filled basin 500 metres up the hill from the great stone pyramid of the visitor centre. The longest core reached down almost six metres (20 feet) into peat that began to accumulate soon after the Ice Age ended. The pollen that rained into the basin from the surrounding hillside records the change from open, grassy tundra to birch scrub then the great spread of hazel and a final, local domination by pine.

It is the sharp, unambiguous decline in tree pollen, at around five metres down in the core and the rise in the pollens of grasses and herbs, such as plantain, dock buttercup, dandelion, hawkweed and whitedover, that marks the taking of land for farming at Ceide.

Something else dramatic happened a bit further down in the core, that is in the period before Ceide's walls. A layer of dark charcoal-rich peat marks a series of intense fires and sand and silt mixed in with it suggests erosion of the mineral soils in the surrounding woodland. Could this be the clearance of the trees carried out by the Ceide farmers? The new study does not rule it out.

Woody charcoal layers like this one have shown up at prehistoric levels beneath bogs all over Ireland, from the Ant rim Plateau and the Sperrins to Clare Island, Connemara and Valentia. Some fires may have been started by lightning, others by Mesolithic hunters driving game. An earlier study by Michael O'Connell, in Connemara, suggested that burning by Bronze-Age farmers, to promote new grass-growth, may have clogged the soil with soot and promoted the growth of blanket bog.

THE Ceide people may have used fire to help clear the hillsides of trees (though Dr Seamas Caulfield, the site's prime investigator has favoured stone axes) but the new core seems to show that as much as 200 years may have passed between the last substantial firing and the main phase of farming. It seems probable that the wall system around the visitor centre was laid out during the lifespan of one or two generations.

The UCG study, using radiocarbon dating, puts the main phase of Ceide farming at between 4,900 and 4,500 years ago, which is near enough to the Mayo 5,000 we lit the bonfires for. The prevailing pollens of grasses and herbs also confirm Dr Caulfield's conviction from the sizes and regular shapes of the fields, that this was pastoral farming of cattle and other livestock. There is also evidence for some cereal growing - most likely wheat - which matches up with the odd plough-mark and stone ploughshare.

The abandonment of the field system seems to have been quite rapid, happening in as little as 50 years. Soil fertility had undoubtedly fallen. But, says the new study, several centuries probably passed before blanket bog began to form on the fields. In the interim, indeed, climate was dry enough to let pine trees root in the" surface of deep bogs in north Mayo, Connemara and elsewhere.

One of the great fascinations about the Ceide Fields - now mapped across more than 1,000, hectares (2,500 acres) of bog - is that their stone-wall field system seems to be totally unique in the record of European Neolithic farming. In other forest clearances of the time, boundaries are irregular and follow the contours of the land but the Ceide settlement, with its series of long, parallel walls, much like those of today's countryside, seems laid out to a plan.

This is certainly what Seamas Caulfield believes. He credits the Ceide people with social organisation and co-operation and speaks of "the landscape as monument".

But Michael O'Connell and Karen Molloy aren't so sure. The stretches of wall that have been uncovered - a tiny percentage of the whole system - appear to have collapsed, spreading the stones. Perhaps, the UCG botanists suggest, the appearance may largely reflect reality - that these were mere linear heaps of stones, Just to clear the land and grow more grass. Perhaps they didn't act as walls at all, in the sense of helping in the management of cattle or giving them shelter from wind and rain.

Even in modern Mayo, walls built of field stones have the habit of slipping apart: those at Ceide had centuries to do so before the bog came. And men clearing land of stones don't usually carry them to dump in neat, painstaking, parallel lines a kilometre long or more - they pile them into heaps.

The issue is far from trivial: the organisation and permanence of field systems are highly relevant to the development of Stone-Age,, settlement and society. "The walls must have served some important practical functions," says the UCG team, "otherwise it is difficult to envisage why so much time and energy was invested to create, a system that was unlikely to have served a ritualistic or cultural function". The inclusion of that word "cultural" may take them on, to delicate ground.