It is mentioned in Irish History that St. Patrick banished all the snakes from Ireland. This seems an impressive feat and we seem to be able to confirm it as fact as Ireland is indeed a country without snakes. However, the more realistic, and more mundane reason why there are no snakes in Ireland is because the country is an island surrounded by the sea. It was separated from the land mass of Europe around 6700 BC before snakes and other varieties of plant life were common in the country. When the Ice Age ended the sea levels rose and Ireland and Britain were both cast away from Europe, hence preventing the spread of snakes to Ireland. The problem with this story is that the first one sounds more impressive. It is important to remember though, that Irish history in the early period up until the 11th century is fragmented and therefore, very difficult to write as truth. What we know is what we believe to be more or less true. Therefore, while the story about St. Patrick is very unlikely, we cannot discard it totally as most of our evidence of the period is very circumstantial. The following is an attempt to introduce Irish history in as clear a way as possible while remembering that much is written as probabilities rather than as hard facts.
After the Ice Age finished Ireland was mostly populated by settlers from Scotland, although there were probably those who came across when there was still a land bridge between the two countries. (Ireland was probably populated before the Ice Age finished but most would have perished during the Ice Age and only the most hardy of life forms would have survived.) Between 7000 and 500 BC Ireland became populated by many different types of people and their cultures, some of whom would leave their mark permanently on the Irish Psyche. .
All of the above settled in Ireland and contributed various skills and expertise such as the ability to use iron and the skill to make pottery.