Clan Donald, also known as Clan MacDonald (Scottish GaelicClann Dòmhnaill ), is a Highland Scottish clan and one of the largest Scottish clans. The Lord Lyon King of Arms who is the Scottish official with responsibility for regulating heraldry in that country, issuing new grants of coats of arms, and serving as the judge of the Court of the Lord Lyon, recognizes under Scottish law the High Chief of Clan Donald. Historically the chiefs of the Clan Donald held the title of Lord of the Isles until 1493 and two of those chiefs also held the title of Earl of Ross until 1476.

The origins of Clan Donald per Wikipedia are:

The Norse-Gaelic Clan Donald traces its descent from Dòmhnall Mac Raghnuill (d. circa 1250), whose father Reginald or Ranald was styled “King of the Isles” and “Lord of Argyll and Kintyre”. Ranald’s father, Somerled was styled “King of the Hebrides”, and was killed campaigning against Malcolm IV of Scotland at the Battle of Renfrew in 1164. Clan Donald shares a descent from Somerled with Clan MacDougall, who trace their lineage from his elder son, Dugall mac Somhairle. Their dynasties are together commonly referred to as the Clann Somhairle. Furthermore, they are descended maternally from both the House of Godred Crovan and the Earls of Orkney, through Somerled’s wife Ragnhildis Ólafsdóttir, daughter of Olaf I GodredssonKing of Mann and the Isles and Ingeborg Haakonsdottir daughter of Haakon PaulssonEarl of Orkney. It remains uncertain if the Clann Somhairle are also descendants in some manner, through one or another of the above dynasts, of the House of Ivar, but this is commonly argued.

However as a result of recent DNA studies, they have shown that Somerled may have been of Norse descent through his male line. By testing the Y-DNA of males bearing the surnames MacDonald, MacDougall, MacAlister, and their variants it was found that a substantial proportion of men tested shared the same Y-DNA and a direct paternal ancestor. This distinct Y-chromosome R1a1 haplotype found in Scotland has been regarded as often showing Norse descent in Britain and Ireland.

There are numerous branches of Clan Donald and several of these have chiefs recognised by the Lord Lyon King of Arms; these are: Clan Macdonald of SleatClan Macdonald of ClanranaldClan MacDonell of GlengarryClan MacDonald of Keppoch, and Clan MacAlister. There are also notable historic branches of Clan Donald without chiefs so-recognised, these are: the Clan MacDonald of DunnyvegClan MacDonald of Lochalsh, the MacDonalds of Glencoe, and the MacDonalds of Ardnamurchan.

BIG Y test results for Clan Donald can be seen via their Clan Donald USA website. To that teams credit,  they have created an extensive McDonald Family Tree – showing all the SNPs for each McDonald sub-clan i.e. Glengarry, Clanranald, Sleat, Keppoch etc. Such SNP Family trees need  to be emulated by other Scottish Clans – if they are ever to be able to solve  the mysteries of their origins.

The McDonald’s that originate from the Norse warrior Somerled, are Haplogroup R1a. This is a distinctive difference, as the majority of Scots Highlanders (such as the Cameron’s) – are R1b.