The Y-DNA profile of the British Isles is heavily influenced by the R1b Haplogroup, by far the commonest in England, Scotland, Ireland and Wales. It is thought to be of relatively recent occupation, and is perhaps associated with both early Celtic migrations as well as German peoples.
The early Celts had come out of the steppe lands to the east of the northern Black Sea region, and it is thought they settled initially near the mouth of the Danube River. Population pressure eventually pushed them west, roughly following the Danube River corridor deeper into Europe, and eventually reaching as far as the Atlantic coast of Europe.
The R1b Haplogroup also includes at least a proportion of the present German population, so that the population of the British Isles that is R1b is a combination of Celtic and the later Saxon migrations.
The I1 Haplogroup is a northern population, and thought to have moved in earlier times into northwest Europe. In the British Isles it reflects the presence of populations of Vikings and other norse settlers, plus Angles, from southern Denmark.
Y-DNA Haplogroups of the British Isles
Mitochondrial DNA (mtDNA) profile of the British Isles
By comparison to the Y-DNA Haplogroups, the mtDNA Haplogroups are more diverse, reflecting a wider origin for the female lineages forming the British Isles' populations.
While the various sub-clades of the H Haplogroup do constitute more than a third of the British Isles populations, several other haplogroups, noticeably J, T, U, and K make up at least eight percent of the populations.
H Haplogroup Subclades
The H Haplogroup of mtDNA is the most common in the British Isles. But there are significant differences in the frequency - and history - of the subclades. A map using 2008 data was created for all Europe by Genebase showing the distribution of the H subclades, and from this was extracted the distribution within the UK.