Wriggling our way into history's hidey-holes

`The floodgates of heaven were opened to overflow exceedingly, and all the fountains of the great deep were broken up; all animated nature became terror-stricken; men fled to the tops of the highest mountains, and the wild animals of the forest sought shelter in the caves.

"There were to be seen in one confused and panic-stricken crowd, the lion and the tiger, the hyena and the bear, the rhinoceros and the elephant, with the fleet horse and the timid hare; and all things breathing life upon the earth lay down, and there at once together died . . ."

In 1859, the year that finally saw Charles Darwin's Origin of Species into print, the creationists (or catastrophists) of Ireland were in vigorous voice. A Mr Edward Brenan of Dungarvan, Co Waterford, was reporting to the Royal Dublin Society on the discovery of the remains of a woolly mammoth, mixed up with fossil bones of bear, horse and hare, in a collapsed limestone cave at nearby Shandon.

He made his find after a quarry workman had paraded a mammoth bone through Dungarvan as that of "an antediluvian giant". Brenan knew better than that, but agreed about the Deluge. Like most Irish geologists, he had been outraged by the theories of a Swiss, Louis Agassiz, who proposed in Dublin in 1840 that Ireland's landscape had been largely shaped by glaciation.

Brenan stuck by the Biblical flood - "an omnipotent agency, capable of accounting satisfactorily for every physical effect hitherto observed on the face of the globe".

He was right about one thing - the flow of glacial water through limestone crevices and caves has left a frustrating heritage for scientists trying to sort out the early history of Ireland's mammals. For example, the richest fossil bone cave so far discovered in Ireland is at Castlepook, on a limestone plateau in Co Cork, explored early this century by the naturalist, Richard Ussher. He gave names to the chambers and labyrinthine passages: Elephant Hall, Fairyland, Gallery of the Aged Carnivores, and so on.

Along with the bones of mammoth, wolf, bear, reindeer, giant deer, lemming and Arctic fox, he found remains of spotted hyaena, now restricted to Africa. But water sweeping through the galleries had left the bones in jumbled piles. In other caves, the deposits were disturbed by human exploration.

All this has made it difficult to fix the comings, goings and extinctions of Ireland's mammals and to match these to the climatic oscillations of the Ice Age. Did hyaenas live here at the same time as the mammoths? Did some of Ireland's "post-glacial" animals actually arrive much sooner?

The answers began to emerge with radiocarbon-dating, but, until recently, this meant destroying whole bones. Up to 34,000 bones had been removed from the Castlepook cave alone, but, as time passed and space grew short, a huge number from this and other sites were "rationalised" (perhaps even downsized) from the collections of the National Museum.

New carbon-14 technology means that a mere gramme of bone is enough, and funding from the National Heritage Council has paid for a large-scale dating programme on museum bones collected from 26 sites throughout the island. The Irish Quaternary Fauna Project was led by archaeologist Dr Peter Woodman of UCC and the results are celebrated in An Post's new set of "extinct animal" stamps, launched last week in the Natural History Museum in Dublin.

Mammoth and giant deer, wolf and brown bear can now be set together in the landscape of some 30,000 years ago, when Ireland was in one of the warmer periods of the Ice Age. Reindeer, red deer, horse and the spotted hyaena were around, too, and probably the stoat. Although a few mammals existed in Ireland before even 40,000 years ago (the hyaena was one), the range of species seems to have built up gradually after that date, perhaps using land or ice bridges across the Irish Sea. At the last glacial maximum, however, about 20,000 years ago, when the ice sheet reached down to north Munster, only mammoth, lemming and fox were certainly present (all at Castlepook).

Some zoologists thought Ireland had a very sparse late-glacial fauna, and that, once the giant deer and reindeer had been knocked out by the temporary but severe return to cold about 10,000 years ago, the post-glacial colonisers were entering a virtually empty island. The new dates, especially from the Plunkett Cave at Keshcorran, Co Sligo, show a much wider range of animals in Ireland after about 12,000 years ago. Stoats, bears, hares and wolves not only shared the giant deer's landscape but could well have survived the 500-year cold phase into the post-glacial era.

The most famous bone caves of Ireland have few secrets left today. Nothing survived the quarrying at Shandon. At Castlepook, where the butts of ESB poles stick down through the roof, cavers from Cork found a part of the cave that Ussher had not worked in, and the late Frank Mitchell was taken to see it.

The only entrance was via a low slit, like a letter-box, in a cave wall three metres thick, through which he was pushed from one end and pulled from the other. In the cones of debris flowing down from ceiling to floor, many modern animal bones protruded, but nothing that could add to Ussher's work in the early 1900s.

The Quaternary Fauna Project ended in no doubt that "a quest must begin for new Irish cave deposits, particularly in areas such as east Waterford" - not least, in the hope of finding human bones from the Pleistocene epoch. Dates from caves in Britain have made it probable that parts of that island had people from 40,000 to 25,000 years ago. Dr Peter Woodman, who has established human presence in Ireland since about 9,000 years ago, thinks it "not unlikely" that some of them reached Ireland during the same period.

Meanwhile, the National Museum is involved in a research programme on a cave in Co Leitrim - one with many bear remains, and a hibernation pit scooped out in the muddy floor. New radiocarbon dates will establish when bears were finally extinguished - probably by Mesolithic settlers about 7,000 years ago.

A Wildlife Narrative, compiled from 10 years of Eye on Nature is now available at £9.99 from all good bookshops and Irish Times Books, fax 01-6718446