Arms of 1702

Genetics and Genealogy

In recent times DNA studies have offered the prospect of cross-referencing historical sources with the findings of modern biological science to arrive at a deeper understanding of the past. This may include the tentative extension of the historical horizon beyond the range of the historical sources by bringing mute prehistoric archaeological remains within a deeper interpretive framework. Such an approach is productive only to the extent that we understand the limitations of DNA testing in confirming, denying and creating historical context. The DNA component most helpful to a deeper understanding of MacLochlainn history and genealogy is the Y-DNA component passed only from father to son within the Y chromosome as being limited to a route of transmission along the male-line it can be seen to independently track the route of transmission putatively followed by both surname and political-legal inheritance within the patriarchal society obtaining in Ireland. Other approaches being the testing of the mtDNA component passed only from mother to child in the X chromosome so quickly limited to a route of transmission along the female-line together with the testing of autosomal DNA reporting the genetic admixture flowing through the multitude of mixed male-female routes of transmission lying between these two extremes are clearly less useful in this context.

Y-DNA studies undertaken to date indicate that the modal average genetic inheritance of those of the surname MacLochlainn having paternal origin in Inishowen is closely associated with the Atlantic Modal Haplotype of the R1b haplogroup having a west to east incline across Europe reaching near saturation point in western Ireland and near vanishing point in Turkey [1]. The recently isolated R1b1c7 subset of R1b in turn encompasses the Irish Modal Haplotype (hereafter referred to as IMH) found particularly heavily concentrated in northwest Ireland in individuals bearing surnames known to have been adopted by segmenting branches of the Uí Néill with a common paternal ancestry indicated around 275AD [2]. This marked founder-effect echoes the great gathering together we find in the medieval genealogies in their convergence of northwest Irish genealogical ascent upon the Uí Néill founder Niall Noígiallach ('Niall of the Nine Hostages') who flourished in the mid-fifth century. A more specific subset of IMH is represented in the MacLochlainn modal haplotype identified by John McLaughlin [3]. Though based upon publicly available data largely self-reported by North Americans unsure of their own paternal origin a coherent MacLochlainn haplotype does seem to have emerged though testing upon a cohort of MacLochlainn males remaining in situ in Inishowen would add greater clarity.

In passing it should be noted that the naive notion that a 'Norse' personal name such as Lochlainn indicates Viking paternal ancestry in the individual bearing the name has been shown to be false in a study containing several individuals with surname MacLochlainn who match the MacLochlainn modal haplotype [4]. We can conclude that in both positive and negative directions the DNA studies to date do not contradict the account given in the medieval genealogies. Indeed the marked founder-effect evident in the IMH mirrors the converging genealogy of the northern Uí Néill to a remarkable degree in both width and depth.



  1. Y-chromosome variation and Irish origins, E.W. Hill et al, Nature 404.
  2. A Y-chromosome signature of hegemony in Gaelic Ireland, L.T. Moore et al, American Journal of Human Genetics 78.
  4. The scale and nature of Viking settlement in Ireland from Y-chromosome admixture analysis, B. McEvoy et al, European Journal of Human Genetics 14.