Why are so many Irish redheads?

There are many redheads in Ireland, England, Scotland, and Wales because of evolutionary reasons. People with red hair usually have pale skin and light color eyes, this has been attributed as a way for them to gain more vitamin D, which comes from sunlight. Because the area of the UK is usually overcast and rainy, the people evolved to have paler skin so that they can absorb more vitamin D, even when it is overcast. This is because even when cloudy during the daytime, rays of the sun's light still shine through the clouds, thus providing little vitamin D.