Science Spin September 2007

The first Hibernians

By Anthony King

It's 8,000 BC, and dawn flickers along an estuary in Antrim. Upstream, hunters emerge from wooden huts on a bluff above the river. Armed with flint-tipped spears, they gaze across the green canopy that runs beyond their settlement. They move out of their forest clearing to spend the day spearing salmon, trapping hare and netting waterfowl.

These are the first Hibernians. Their lifestyle, gathering and hunting for food, persisted until the arrival of farming 3,000 years later. Scientists and archaeologists have put together the first reels of human activity in Ireland, a story set in vast woodlands and wetlands, inhabited by lynx, bears and wolves.

First settlers

Cut to a field along the River Bann in 1974. A routine excavation has just located the earliest Stone Age settlement in Ireland. Peter Woodman, Professor of Archaeology at UCC, and his team unearth flint axes, spear tips, evidence of wooden huts and an assortment of animal bones from Mount Sandel. Last year, radiocarbon dating of hazelnuts from this site showed it to be around 10,000 years old.

Professor Woodman believes we have frequently underestimated these Mesolithic people. "One thing that has come out of recent research is that these people were successful and had a significant presence in many parts of the island," he said. The people along the River Bann chose the site with care, he told Science Spin.

They had access to salmon and eel runs and shellfish and seabirds along the coast. Professor Woodman's excavations uncovered the charred bones of hare, wild pig, and a mix of birds including wood grouse, divers, mallards, teal, goshawk and woodcock. Stores of hazelnuts and water lily seeds were also found.

Forests and wetlands

Fifteen hundred years before man's arrival, Ireland's climate had experienced a rapid rise in temperature. "Ireland had gone from an Arctic climate to a climate similar to today within a decade," said Dr Fraser Mitchell, a botanist in TCD. The first trees to arrive into Ireland after the Ice Age were juniper and birch. Unsuited to growing in shade, these early colonists were replaced by a succession of other trees.

By the time man arrived, the forests were dominated by pine, oak, elm and hazel. Dr Mitchell has studied the migration of these trees into Ireland. He said Irish trees most likely originated from Iberia, a refuge for temperate trees during the last Ice Age. When conditions improved, they migrated up the Atlantic coast of France and across the Celtic Sea. Recent genetic studies of oak bolster this continental origin for Irish trees.

By the time of the Bann people, Ireland was a wooded island with large lakes in the midlands. It was an Ireland without bogs; in their place were lakes, shallow fens and marshes. Coastal wetlands were also far more extensive. Studies of ancient pollen indicate that the forests varied according to factors such as soil, local climate, and altitude.

Elm woods with an 'under-story' of hazel blanketed the fertile limestone soils of the midlands, while oak and pine thrived on more acid soils in the west and east and in upland areas.

It would be wrong to picture a homogenous wooded landscape, however. "There would have been lesser trees that added great beauty like hawthorn, wild apples and holly, as well as some clear areas with grasses and flowering plants," said Professor Valerie Hall, a botanist at QUB. She said that there were plenty of plants to provide food for early settlers. "There were 120 flowering plants in Ireland you could eat."

Prey gap

The animal life of Ireland 10,000 years ago was very different from Britain. Predators there could feast on red deer, roe deer, wild cattle and elk; Ireland had none of these species. Despite missing out on large herbivores, fierce meat eaters prowled the Irish countryside, including bears, lynx, stoats and wolves.

What were these animals eating? It's a question that intrigues ecologist Dr Paddy Sleeman of the Department of Zoology, Ecology and Plant Science, UCC: "I'm interested in what fills this prey gap." The main mammal prey of the River Bann people was pig. "If you take the pigs out, if they were introduced by man, you have an ecosystem that doesn't function properly." Dr Sleeman has suggested migratory species may have sustained the meat eaters.

Nigel Monaghan, keeper at the Museum of Natural History, agrees that ground birds were probably a major source of summer food for the predators. He compared Ireland at this time to today's Arctic, where birds migrate during summer to breed in relative safety.

Nigel is an authority on extinct Irish mammals and has studied the bones of brown bear and lynx. Evidence for such animals comes from excavations of caves and accidental finds brought to the museum over the last 200 years. The bone collection offers an incomplete picture: "We probably know a lot fewer animals than actually lived in the landscape at that time," he said.

Chance events colour what we can learn of prehistory. Bear bones are common because they hibernated and frequently died in caves. Nigel believes lynx were reasonably abundant in the Irish countryside, probably preying on Irish hares. But there is just a single record of this cat. "We wouldn't know about lynx except for one cave in Waterford where people took the trouble to excavate every bone and came up with an oddity that turned out to be a lynx," he said.

There are lynx bones from Roman times in Britain, yet no written records mention them. It's difficult to say how long this animal dined on Irish hares. Recent radiocarbon dating of bear bones proved they lived in Ireland 3,000 years ago, far later than had been assumed.

Natives and colonists

Many textbooks will tell you Ireland remained linked to Britain or Europe long after the ice melted, but this is an outmoded view. Geologists now say Ireland has been an island since at least 13,000 years ago. If Ireland was isolated before it was warm enough for postglacial mammals and plants to live here, how did animals reach this island?

The experts increasingly believe most didn't arrive under their own steam, and the canon of true natives is shrinking. Rabbit, hedgehog, and fallow deer were brought in by the Anglo-Normans.

Grey squirrel, bank vole and mink were subsequent introductions or escapees. Now, genetic evidence has added wood mouse and pygmy shrew to the non-native list. Red deer are also being relegated to "blow-in" status; a "bread-and-butter species" for early European hunters, their remains are not found in Ireland until 3,000 BC.

It has even been suggested that bears and wolves might have been brought to Ireland by man. These animals are unlikely to sit at the end of a dugout canoe waiting for a trip, but their cubs make for cute, manageable bundles.

Does it matter what is native or non-native? Nigel believes these are emotive terms, suggesting some animals belong while others do not. "It's far more instructive to look at whether an animal is in balance in its landscape." An animal like the grey squirrel is a concern because it is expanding rapidly and causing ecological upset, he said. Moreover, almost nothing is native if you go back to the peak of the last Ice Age; go back further and wild horses, spotted hyena and reindeer were native Irish mammals.

Ecosystem

Dr Sleeman warned against comparing our wildlife with our nearest neighbour. "It is a mistake to look at the British fauna and think it's typical and see our own fauna as impoverished." Better, he said, to view it as a unique postglacial island fauna.

Ireland differs from Britain, which only became an island 7,000 years ago, not just in terms of animals. Certain trees never made it to Ireland. "Beech grows well in Ireland, but is not native," said Dr Mitchell. It got as far as the Welsh coast 1,000 years ago. Lime reached the Welsh coast over 7,000 years ago, but never crossed the Irish Sea. Mitchell said this is a real example of the Irish Sea acting as a barrier because lime grows quiet happily here.

One group of animals that did cross the sea were the birds. Ireland 10,000 years ago must have had a rich and diverse avifauna. Gordon D'Arcy, author of 'Ireland's Lost Birds', said Ireland now has six birds of prey, but should probably have twelve.

It is impossible to say for sure which birds were here, however. The Museum of Natural History has bird bones in its collection, but they are yet to be fully described and dated. We can make a good guess from the birds that live in similar habitats in Europe and from written records from historical times.

Gordon envisions the large game bird capercaille dining on pine shoots and cones in the primeval woods while woodpeckers drum out insects from bark. Goshawks likely hunted grouse and songbirds, while they themselves watched for eagle owls. The wetlands hosted cranes, bitterns and perhaps storks, along with birds of prey like the marsh harrier, osprey and white-tailed eagle.

Humans
Early settlers had little direct impact on these birds or the landscape in general. Due to the absence of large game animals, experts say people had little reason to create clearings for hunting, as occurred in Britain.

They may have altered the nascent ecosystem, however, by bringing wildlife with them, whether by accident or design. Also, they could have had dramatic local impacts, such as wiping out colonies of flightless great auk by eating adults and collecting eggs. It wasn't until the arrival of farming that the landscape was radically altered.

The hunters of Mount Sandel would have great difficulty recognising modern Ireland. The landscape, animals and even sea level of today bear little resemblance to the early post-glacial Ireland that they knew.

Reconstructing their environment means knitting together details from botany, archaeology, geology, zoology and genetics. Researchers have used ancient pollen and insects, cave remains, and DNA from living and dead animals to add to the picture. The rerunning of past episodes of ecological change should offer better insight into Ireland's past and present environment.

Bear bones
For thousands of years, a walk in the woods could have brought you nose-to-nose with an Irish bear. Recent radiocarbon dating of bear bones from the Sligo-Leitrim area has shown bears survived in Ireland until 3,000 years ago. Loss of forest to agriculture pushed the bears to their last stronghold in the west, said Nigel Monaghan. Hunting may then have reduced their numbers to unsustainable levels. Apart from carbon for dating, bones also yield DNA.

Dr Ceiridwen Edwards of TCD, an expert in ancient DNA, is interested in where the bears came from. Last year, she isolated DNA from bear bones from all over Ireland. Edwards hopes the DNA will show the origins of Irish bears and indicate how they are related to their living and extinct brethren in Europe.

Pollen and Insects

The main evidence for prehistoric woodlands comes from pollen. Pollen is made from one of the most indestructible organic materials and lasts millions of years in permanently wet or permanently dry places. Researchers obtain records of ancient pollen by using a hollow borer to extract a core from a lake or peat bog. An expert then counts and identifies the pollen to work out the vegetation of that time.

Wind-pollinated trees produce huge quantities of pollen, whereas insect-pollinated trees and herbaceous plants produce much smaller amounts. These and other factors must be taken into account when interpreting the pollen record. And these interpretations have led to vigorous debates. Some experts say pollen overemphasises the forests; they suggest primeval Europe looked more like pasture woodland or even parkland.

One way of solving this mystery is to look at beetles. The remains of these insects preserve well and are extremely useful because specific groups of beetles live in specific micro-habitats. Dr Nicki Whitehouse of QUB recently used fossil beetles to study forest history in Ireland. According to Dr Whitehouse, the dispersal and decline of these insects can tell us about the nature and role of human activities in shaping the European landscape over the past 10,000 years.