Answers to Questions by Yair Davidiy (29 November 2017, 11 Kislev, 5778)
If the red-haired Irish look that way from breeding with Scandinavians, and the black-haired Irish look that way from breeding with the Spanish, what did the original Irish look like?
https://www.quora.com/If-the-red-haired-Irish-look-that-way-from-breeding-with-Scandinavians-and-the-black-haired-Irish-look-that-way-from-breeding-with-the-Spanish-what-did-the-original-Irish-look-like/answer/Yair-Davidiy
The map shows the distribution of the YDNA haplogroup R222. This is associated with Niel. The Scandinavians got their red hair when they were conquered by Irishmen from Ireland led by Neil and his descendants. Later migration operated in the other direction with the Vikings from Norway and Denmark coming and settling in areas where descendants of Neil were not that prominent.
Red hair is much more common in Ireland than it is in Norway. Areas of Viking settlement in Ireland do not overlap with those where red hair is more common.
On the other hand regions in which the R-222 gene for Nial and his kin in both Scotland and Ireland are also those in which red hair is more frequent. Irish legend says that Nial ruled over most of Ireland and Scotland and parts of Norway. Red hair is not gender specific so it may be inherited via either the male or female sides. Red hair was therefore in Ireland long before the Vikings came.
 Irish histories traced their ancestors to several sources. Apart from giants and fairy peoples (leprechauns, etc) there were no original Irish, just groups from different places who settled in different regions. The Tribe of the god Dana is often described as being of golden hair. The Fomorians are sometimes described as blondish and at other times as dark. The Bolgae are usually assumed to have been brunettes and smaller in statue but not overduly so. The Milesians were the majority and they came later. They are also described as often being blond or golden of hair but less markedly. Nial belonged to the Milesians who were also known as Scotti. Nial was the first High King of Ireland. Many of the Irish Royal families have the mark of Nial. Then came the Vikings, and the Norman-English, and the later English. There were also a few Jews and Spaniards but their presence has not been emphasized. The overall picture of DNA of Ireland is quite homogeneous. This also raises questions. Has environment (rather than heredity alone) had a greater influence on DNA than is commonly admitted?
Maurice Hynds commented on Facebook: This article totally ignores the pre-Gaelic so called Irish. The ancient Ulster people, the Cruithin who have been suggested to have had middle eastern origins.