Historians often debate questions of when people first came to Ireland, and theorize what race of people(s) were first to arrive.

We know little about Ireland a million years ago. The cenozoic period started 70 million years ago and continues today. Now the earth has experienced about 20 Ice Ages, each producing large continental size ice sheets which enveloped land wherever they went.

Starting 40,000 years ago we know substantially more; Ireland was heavily forested and mountains were taller.

This profile began to change 30,000 years ago with the onset of the last and current ice age. Sheets of ice marched inexorably from the Scandinavian arctic south for 10,000 years to finally lock Ireland in it's icy grip. The glaciers extended south to Munster, but left Cork and Kerry relatively ice free.

20,000 years ago the ice started to melt and the ocean began to rise from 400 feet below sea level up to present level.

Then Galway Bay was a fresh water lake and the Aran Islands sat on a limestone shelf 100 to 400 feet thick forming an ocean blocking arc of burren limestone connecting the land south of Galway with the land north of Galway.

Sometime around 9,000 years ago the temperature of Ireland became people friendly and from that point on could theoretically support agriculture.


Read about ice age Ireland here.