Part of the reason Iām learning Welsh is because this is a view Iāve held for a while anyway. Iām not Welsh (actually I have Irish ancestry) but I consider Welsh to be the descendant language of that spoken by the original inhabitants of these islands, and therefore a link to our shared past.
I think this is questionable. It seems likely from place name evidence, that a pre-Celtic language was spoken in Britain during Neolithic times. Names such as Ouse (the river) and MĆ“n (the island) donāt appear to come from an Indo-European language. Itās possible that the language(s) spoken in what is now Britain from the end of the ice age until maybe the Neolithic revolution was/were related to modern Basque, but thereās a lot of supposition involved.
Iāve seen an exhibit based on this work in the Natural History Museum in Oxford - and was talking to @johnwilliams_6 about it (to the limited extent of our ability to discuss Y-chromosome haplotypes in Welsh!). Itās really very interesting in that as you look at the results in increasing detail (effectively zooming in, so to speak) these various sub-populations seem to just emerge from the data, that correspond quite closely with old political entities: on a broad view, weāre very much all one island, but then you see not only that Scotland and Wales are different from England, and that the Kingdom of Gwynedd is different from Dyfed, but also little patches like the one around Leeds that appears to be Elmet.
Probably, but itās good enough for me! And in any case, itās certainly more āBritishā than English!
Geeky fact - British was used to refer to the Welsh into the Elizabethan era (that would be the first one) before it was appropriated by the English.
Iām not sure that appropriated is quite the correct word. After all British was already an English word at the time!
But, yes, British was what the Welsh language and people were called by many. And then the crowns of Englandandwales and Scotland were united, and a century later the parliaments too, and a terminology was required to describe the new state/nation/people that (the ruling class hoped) had been created. So they went back to a time when they thought the island had last had a single people/culture and came up with British, and the meaning of the word quite rapidly changed.
Most of what Iāve read suggests there were people living in the British Isles before the Celts arrived. Sadly we know little about them and can only speculate.
Itās really good that these studies are being done now so that humanities history can be traced genetically. They only used people with 4 grandparents living within 80km of each other. Very soon such studies will be impossible and the data a lot more messy and very much harder to interpret because everyone moves around so much now.
You have to be really careful with stuff like this, Gareth. People are not fruit flies - they are not defined by their genetic make-up, but by the cultural baggage they carry around with them. So when you talk about the āCeltsā arriving, you are talking about the arrival of a culture, and very much less about the arrival of a people (thereās vanishingly little evidence that a Celtic āpeopleā or even less āraceā ever existed).
Certainly there have been periodic injections of new DNA into the population Britain over the millennia, but compared to the vast cultural changes that have taken place, their effects have been relatively small - the biggest DNA replacement probably having been the pre-Celtic Beaker People many thousands of years ago.
Take a look, for example, at the Norman Conquest - which was over and settled in England within a few years but arguably wasnāt settled in Wales until 1282, or 1415 or maybe even 1535 depending on how you view it. This consisted of the replacement of the English aristocracy with Norman lords, maybe 2000 people in a population of possibly 3 million, yet the political,economic and cultural changes were huge. The genetic effect is hardly noticeable, but culturally it changed the history of not only the British Isles, but arguably the whole world.
In broad terms, I agree with this wholeheartedly - you can get into such a mess of unspoken assumptions with some of this stuff. (Like, if youāre looking at matrilineal vs patrilineal DNA, are you assuming men conquer, women settle -and if so, is that valid, etc.) Itās also potentially Blood-and-Soil kind of stuff that - while Iāve thankfully seen no sign of that anywhere on this forum, ever - plays into the hands of racists.
And to an overwhelming extent weāve got a lot in common anyway. My brother had his DNA ādoneā and all it really revealed was that we were āDoggerlandersā - mostly from one or other of the groups of people who probably lived in Northwestern Europe at the time the Ice Ages made the Dogger Bank habitable and joined us onto Europe. Culturally, Iām 100% English - and to what extent I may be āactuallyā Anglo-Saxon, āactuallyā conquered Celt, āactuallyā Beaker Person is for me mostly unimportant as well as unknowable.
But this is precisely why I find the emergence from the data of some of these smaller sub-populations really surprising - like, Norman conquest (big deal historically, genetically negligible) vs lost Kingdom of Elmet (gone and near-forgotten, still there in the gene-pool). Approached with due caution, I think itās fascinating.
Undoubtedly fascinating. 
Absolutely STILL not a done deal if you ask meā¦ 
I agree with the general caution expressed by several people about making assumptions / guesses about our genetic inheritance in these islands generally.
But Iām happy and feel fairly safe in saying that modern Welsh is a good representative of a language that was more widely spoken (in probably various forms) in a good deal of the island of Britain at one time, predating the Saxons, Vikings and definitely the Normans.
Worth learning and promoting for that, among other very good reasons.
Yes, I probably sometimes forget. There is a huge difference between culture and genetics in humans and very little point in looking into except in the broadest sense. In other creatures there is a much closer relationship. The point I was making that the era of being able to trace population movements in humans is coming to an end. There is a traceable genetic pattern of all humans, the āOut of Africaā theory, which is perhaps ending now with an almost random (from a biological perspective) of individuals movement across the globe.
The Celts were themselves invaders to these islands- relatively recent arrivals in the bigger scheme of human history. 
In north america, native people had traded in copper, but gold had no value to them. If you then look at the Klondike gold rush, then you get massive immigration and wealth creation.
Maybe silver and gold had that effect in these islands. This is a map of valuable minerals in the UK - make of it what you like.
Thinking a bit more. Culture is not about genetics or who was where or when, itās about traditions and long lasting influences. If you go to Seville in April, little children and grandparents are instinctively clapping and moving in unison to rhythms that transcend more than a thousand years of history and itās really moving.
Celtic culture started in or even before the bronze age and itās influences and reach were huge. There are only a few places and pockets of peoples who have continued tbose traditions and influences and Wales is a place where influences from long ago have endured. Itās magical really and quite inspirational.
Well if you can find a modern language descended from that spoken by the people before the Celts then Iāll switch to thatā¦ but until then, Welsh is good enough!
Oh Welsh is definitely good enough!
But my point stands.
Ive just seen Geraint Thomas voted BBC sports personality of the year, but if you were ever voting for the greatest Welsh person of all time then it has to be Nennius.
Who was he - he may have even been invented himself which is part of the mystery.
Apparently, a reclusive ninth century Monk from Mid Wales. A student of someone from Bangor who as his teacher definitely changed the British date for Easter.
Nennius didnāt invent Arthur, but was someone who woke the whole of Europe and the modern world up to the fascination with one of the most iconic figures in world history - history or fable who knows and who cares.
He before Geoffrey of Monmouth created the modern day mythology or possibly created a link to some unknown truth - such is the mystery and intrigue.
People will debate endlessly about Arthur and Arthurian legends, but that has all come about because of great Welsh storytelling from people like Nennius.