Recently sequenced Roman, Iron Age and Anglo-Saxon DNA sequences from England help to clarify the issue of the impact of Germanic migrations in Great Britain, which seems to have been significant.
Rui Martiniano et al., Genomic signals of migration and continuity in Britain before the Anglo-Saxons. Nature 2016. Open access → LINK [doi:10.1038/ncomms10326]
The purported migrations that have formed the peoples of Britain have been the focus of generations of scholarly controversy. However, this has not benefited from direct analyses of ancient genomes. Here we report nine ancient genomes (~1 ×) of individuals from northern Britain: seven from a Roman era York cemetery, bookended by earlier Iron-Age and later Anglo-Saxon burials. Six of the Roman genomes show affinity with modern British Celtic populations, particularly Welsh, but significantly diverge from populations from Yorkshire and other eastern English samples. They also show similarity with the earlier Iron-Age genome, suggesting population continuity, but differ from the later Anglo-Saxon genome. This pattern concords with profound impact of migrations in the Anglo-Saxon period. Strikingly, one Roman skeleton shows a clear signal of exogenous origin, with affinities pointing towards the Middle East, confirming the cosmopolitan character of the Empire, even at its northernmost fringes.
Notice that I say Germanic rather than Anglo-Saxon because I'm not sure how much can be attributed to these and how much to Vikings, whose genomes were similar. A recent study on British genetics seemed to indicate that the Danish (Viking) origins were clearly more important than the Saxon ones from Low Germany. However... were the original Angles more akin to Saxons or to Danes?
Anyway, the ancient samples are mostly Romano-Briton, from burials at Driffield Terrace, near York (Eboracum), dating to c. 200 BCE and including many decapitated remains. Another sample is from the Iron Age of Melton (East Yorkshire), dated between 200 and 40 CE. Finally a Christian Anglo-Saxon individual from Norton (Teesside, 70 Km north of York), dated sometime between the 7th to 10th centuries.
Excepted one Roman era outlier (3DRIF-26), who seems an immigrant from the Eastern Mediterranean (autosomal DNA strongly suggests the Levant or Arabia), the rest all fit well with the autosomal genetics of the Iron Age one and modern Welsh. Modern English seem to have, in most cases, at least some Germanic admixture:
Using the Dutch average as proxy for continental Germanics and the Welsh average for Romano-Britons, it would seem that modern English are on average, about 1/3 drifted towards Germanics, while the ancient Anglosaxon from Teesside was a bit more than half drifted in that direction. He was still within modern English variance, although rather towards the Germanic extreme of it.
The Iron Age sample was a woman with mtDNA haplogroup U2e1e.
The Romano-Brithons (all men), excluding the Eastern Mediterranean outlier, carried all variants of Y-DNA haplogroup R1b1a2a1-M412. It is notable that M405/U106 ("North Sea" subclade) was found in two of them, so it cannot be attributed to Germanic immigration. Another carried a sublineage of the M529 ("Irish") subclade (common also in Great Britain) and two others of the S28/U152 ("Alpine") sublineage (less common in Britain). The remaining two carried upstream L52* (generic "West European") paragroup lineages. See this entry for overall distribution details.
Their matrilineages were all subclades of H1, H2, H6 and J1. Details can be found in table 1.
The outlier carried Y-DNA J2-L228 and mtDNA H5. The patrilineage fits well with a West Asian origin (an Italian one also fits) but the matrilineage is much more common in SE Europe, although it also reaches high frequencies in Wales. However the ADMIXTURE analysis strongly negates the possibility that he was European and very clearly supports a West Asian origin instead.
Finally the Anglo-Saxon man carried Y-DNA lineage I1 (most common in Sweden but scattered at low frequencies through Europe) and mtDNA H1.
The authors estimate that Iron Age and Romano-British samples were typically brunette with brown eyes. There is one exception though, 6DRIF-18, who was probably blond and blue-eyed, as was surely the Anglo-Saxon.
Blood type O was inferred for all Iron Age and Roman era samples, except 6DRIF-22 who was A. The Anglo-Saxon one may have carried type B or A (or AB?)