During the Ice Age, not only was the planet much colder, with ice sheets covering much of what we call the northern hemisphere today, but, crucially, it was much drier. In Ireland, we often associate the cold with the wet but if it is really cold, there is far less evaporation, fewer clouds, and less rain. Our world in the Ice Age was cold and dry, meaning it was difficult for plants to grow. In this type of climate, farming isn't an option: it's too risky to depend on any one piece of land to produce the energy you need. As the temperature rose and the ice caps melted, we experienced a sudden explosion of life. The world got warmer and wetter, and people started to live around places where they could make food grow most intensively. This didn't happen overnight; it probably took thousands of years, with hunter-gatherers foraging and hunting, while doing a little side hustle in farming.