More info about the Dna article 'Norse Code' in Natue magazine. Prof Alice Roberts's (edited due to length) social media post: "My friend Pontus Skoglund and his colleagues have JUST published this incredible new piece of research into Viking-era migrations - using ancient DNA and a brand analysis called Twigstats. [......] This new analysis includes a new piece of information relating to [.....] the remains of 30+ individuals from a mass grave in Oxford, thought to have been slaughtered in the 1002 St Brice’s Day Massacre, [......]. Ancient DNA analysis is an incredibly powerful tool for understanding populations, migrations and families [.....]. This is really exciting science. And it’s really hard. First the archaeogeneticists have to take samples from ancient bones, then they extract DNA from the samples [......]. Ancient DNA might survive the ravages of time - but it’s usually broken up into tiny pieces, [......]. So the next stage is assembling those segments of code into a whole genome. It’s a mindblowingly huge puzzle which is only made possible with advances in computing power. But reconstructing an ancient genome is just the beginning. What the archaeogeneticists are really interested in is comparing lots of genomes - looking for similarities and differences. These are the key to understanding what was happening to populations in the past - and tracking migrations. Over time, genomes acquire new mutations. Those mutations will be inherited by descendants of the person in whom the mutation first arose. While most of the genome will be identical between two people, the pattern of these little differences is crucial for working out what happened to populations over time - and for tracking families. [.......]. Pontus told me that distinguishing different Iron Age Scandinavian groups, for instance, is MUCH harder. It’s not a perfect analogy, but imagine trying to tell if someone is Norwegian or Danish by the appearance - it’s hard. But Twigstats works by focusing on salient differences - and these are ones related to relatively recent mutations [......]. It ignores older mutations which have been sifted and sorted through populations over time, creating confusing ‘noise’. So it’s a bit like snipping a twig off a gene tree so you can focus on just those branches - ignoring the rest of the tree. Hence the name: Twigstats. This means you can now spot subtle but important differences between populations that are quite genetically similar. And then this also means you can spot when in time a population starts to look more similar to another one - implying that those populations have merged with each other. In other words: some people have migrated and settled in a new place and started to mix with the population already there. Pontus and his colleagues tested their new technique on simulated data to make sure it worked - which it did, very well. Ten times better than anything else they’d tried before. They used it to look at some real samples, looking at modern human and Neanderthal DNA - to test a criticism of the theory that these species interbred with each other in the Palaeolithic. Now this is something I’ve been following for years, ever since my first big landmark series for the BBC, The Incredible Human Journey. Back then, in 2008, there didn’t seem to be any evidence of modern humans (Homo sapiens) and Neanderthals mixing. At least, fossil bones weren’t providing a suggestion of interbreeding. But then ancient DNA came along - with the first Neanderthal genome published in 2010. And then it seemed there was evidence for interbreeding, around 60,000 years ago. But a few scientists have criticised this claim, saying that the patterns in the modern human DNA could have happened another way, just through genetic variants being sorted over time, creating a sort of mirage of an interbreeding event with Neanderthals. Most archaeogeneticists still thought that interbreeding explained the pattern. But there was an element of doubt. [....] Twigstats finally puts that doubt to bed. Neanderthals and modern humans definitely met up and swapped genes with each other (delicately put). [.......] The main focus of the study was the later first millennium - the Viking Age. And here, Pontus and his colleagues were able to use Twigstats to track migrations of different populations that have been difficult to ‘see’ before, they’re all so similar. They found evidence for migrations of Germanic people southward into Poland and Slovakia, as well as into south-central Europe and Britain. And then later, those people that ended up in Poland were themselves replaced during the Slavic period. They also found evidence of a previously unknown migration into Scandinavia, before the Viking Age - transforming the ancestry of Denmark and southern Sweden. Interestingly, this seems to coincide with a change in runic script and language - establishing Old Norse and the Younger Futhark."