DF19 is a SNP mutation that defines one of the smaller subclades below R-P312, which is the most common Y-haplogroup in Western Europe (DF19 may be as large as 6-10% of all R-P312). The DF19 mutation most likely happened in a R-P312* man who was born in southern Scandinavia or possibly the northern Germanic coastal region, presumably somewhere around 2400 BC. Shortly after the origin of DF19, the R-DF19 haplogroup was already divided into two major subclades, characterised by the DF88 and Z302 mutations, respectively. During later centuries, the male descendants of the DF19 ancestor could be found among the northern and western Germanic tribes that spread out across Scandinavia, Germany and the Low Countries. At the time of the great migrations (4th – 6th century AD) the DF19 mutation was most likely present in all major Germanic tribes in that area, alongside other YDNA-Haplogroups such as R-U106, I1 and R-L238. The mass migrations of the Saxons, Angles, Jutes and Frisians have likely been responsible for a first geographic spread of DF19 and its subclades towards the British Isles and across Western Europe. Through the southward expansion of the Saxons, the Franks and later the Vikings, Y-chromosomes carrying the DF19 mutation also started appearing in the rest of Western and Central Europe. However, many of the British R-DF19 lineages seem to have left their ancestral homelands in southern Scandinavia only during the Viking age. Between ca. 800 and ca. 1100 AD, Viking raiders and settlers brought the DF19 mutation to Ireland, Scotland, England and Normandy. In 1066 the Normans invaded England, and quite a few of them (probably descendants of the - predominantly Danish - Vikings that had settled in Normandy in the early 900s AD) belonged to the R-DF19 haplogroup. Our analysis of more than 210 Big-Y test results has led to an updated YTree for the R-DF19 haplogroup, which has been posted on this website in the "Photos" section, under: Draft R-DF19 YTree (YSNP Names & Addresses) from 2017-06-12. We have already been able to position more than 880 shared DF19 SNP mutations in this hierarchical overview, whereas previously only six SNPs were officially known below DF19 (namely DF88, Z302, L719, L644, L1199 and L1200). Each of these non-private "shared" SNPs has been detected in the Y-chromosome of at least two test persons, and in principle every single SNP represents a common male ancestor that was shared by all test persons that carry that SNP. On average, about 42-48+ SNPs younger than DF19 have been reliably detected in each of the Big-Y-tested samples, which corresponds to approximately one new SNP every 80 years, or roughly every 2–4 generations. This implies that new side branches of known male lineages can be quite accurately positioned in the R-DF19 YTree, thanks to the enthusiastic participation of so many of our project members.