Friday, 16 February 2018

Where do we III come from?

My sense of identity really hasn't exercised me in any emotional way. Coming from Horse-riding-Protestant stock from King's County, my sense of self, and expectation of entitlement, is bred in my bones. Being straight, white, male and middle-class helps too. We know exactly when our family established its patrimony in Ireland - 1643 - and the manor house in Wales from which we migrated. The family takes this ancestry schtick with a pinch of salt, a dollop of humility and a wry smile knowing that my great grandfather was the 'natural son' of the owner of the Big House. My PhD thesis hinged on the idea that by looking at present day populations we could infer something about their ancestry and therefore inform people about the pattern of colonial migration in New England and the Canadian Maritimes. A similar analysis can be driven by looking at much richer and more extensive data of European human genomic DNA variation.

I've looked at this sort of analysis before I through 23andMe, and II though linguistic analysis, and also meanderings about PIE. We are now a little but more confident about where the Brits come from. We used to do this all the time in population genetics and molecular evolution: we inferred ancestral states from present day DNA because the dead are dead and disintegrated beyond yielding sequencable DNA.

Not any more! The technology for making sense of ancient DNA has moved on really fast and far in this century. The person who has delivered the most quality ancient human material into the public domain could well be Lara Cassidy [R], a 20-something PhD candidate working in Dan Bradley's [bloboprev] Archaeological Genetics lab in Trinity College Dublin. Ancient DNA work is really difficult: you need to be a good pair of hands: dexterous, meticulous, painstaking, tidy in your habits and careful of your data.  Any DNA that exists from hundreds or thousands of years ago is going to be degraded, fragmentary and hard to recover. The least bit of contamination: a fallen eyelash or a fingerprint; something left from your last experiment; a cough from the cleaner; will deliver enough contaminating DNA to swamp out any signal from your current sample. Then you must have a completely different set of skills in computational analysis, number crunching and programming. Ancient DNA is like running a time machine: from a fragment of bone [preferably the 'petrous' bone near the ear-hole] we can see certain attributes of the long-ago dead: their sex; their skin, eye and hair colour; their probable height; their susceptibility to disease. It's as if Achilles or C├║chulainn walks again. Cassidy has knocked off numerous ancient DNA genomes! A life-time's work in 4 years.

One of the most fraught questions in Irish departments of archaeology and anthropology is whether we are the direct, genetic, descendants of the builders of Newgrange and the folk of antient legend. Did those people adopt the cultural practices and borrow the tools of more sophisticated neighbours or were those ancient people displaced by the bearers of those tools and artefacts? 100+ years ago, with the British Empire as the invisible background to cultural discourse, the consensus was that superior migrants had brought culture to the benighted West. The next generation was throwing shapes about national identity after a bloody war of independence and 'migration' became a dirty word. The next generation after that adopted a bit of this a bit of that compromise position. Cassidy and her co-workers have now dumped a sackful of data on the fossil-cluttered desks of archaeologists and shown, maybe uncomfortably, that the colonial invasion / physical displacement model is most likely true. Here's the data graphed out [explanatory background yest]:

The further back you go, the thinner the seam of data gets. The earliest DNAccesible human bones in Ireland were discovered by spelunkers in a limestone cave in the NW. They have been carbon dated to the Mesolithic and their owners /users were probably hunter-gatherers. But in terms of Eurogenetics, those bones are on another planet.
A more recent, and much better preserved skull [L reconstructed head of Our Lady of Ballynahatty] was unearthed at Ballynahatty near Belfast. She is Neolithic and from an era that had embraced farming. The largest cultural artifact of that era, 120km due S but still in Ireland is Newgrange: a mighty pile of engineered stones, some decorated, some sorted by colour, protecting a portal tomb whose access passage precisely aligns with the Winter Solstice. It is older than Stonehenge, older than the Pyramids at Giza.  Her DNA profile [marked Bh above] bares no genetic resemblance to modern Irish people but slides neatly into place between Spain and Sardinia; she was clearly European but not our sort of European.

1,000 years later, another cultural transition appears in the archaeological record. It is fatuous and just wrong to think of the Neolithic society which created Newgrange [and the Ringstone, of which we are Guardians] as "banging two rocks together". That society was cohesive, sophisticated, religious, hierarchical and driven by the aesthetic. But the metalworkers from The East bringing copper and tin together in durable bronze weapons & knives; gold fancy-goods; and distinctive domestic pottery were a different culture altogether. The team from Trinity have shown clearly that they were different genetically as as well. Three Bronze Age skulls from Rathlin Island off the Antrim coast of Northern Ireland have now also had their genomes exposed to the public gaze. They are a bit on the edge of the local modern demographic [marked Ra on the genetic map above] but recognisably of and from these WEA islands. It's all been published in, the prestigious, PNAS.

You might think that Lara Cassidy is lucky to have gotten such a fabulous project with which to get her start in science [7 peer-reviewed pubs; two as 1st author; 1 in Science 2 in PNAS; not to mention all the press coverage]. It is not always like that: with the best will and skill in the world you can sign up to a project which has no hope of working out because it has been poorly conceived or grossly underfunded or has an terrible supervisor. But that project was lucky to get Cassidy because her telegraphic CV indicates quite extraordinary levels of achievement = determination and dedication. I've suggested before that you make your own luck, through finding a good fit to your talents and working damned hard at your craft. You can almost hear a Professor Bracknell echoing Oscar Wilde with "To sequence one ancient genome, Ms Cassidy, looks like fortune; to sequence several looks like carefulness." 
Bob B'godde Bracknell I wish I'd said that.
Bracknell: You will, Bob, you will next [last] time you are invited to Commons at TCD

but it's not about me, it's about More women in science.

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