Until now it was thought that humans first arrived in Ireland in about 8000 BC. Now a butchered bear bone has proven that they were there as early as about 10500 BC. Per the article:
For decades, the earliest evidence of human life in Ireland dated from 8,000 BC. But radiocarbon dating of a bear’s knee bone indicated it had been butchered by a human in about 10,500 BC — some 12,500 years ago and far earlier than the previous date.