Stiofan75
The National Geographis site below might give you some useful info on soem of the terminology.
https://genographic.nationalgeographic.com/genographic/lan/en/population.html
What you refer to as a DNA strand is called a Haplogroup which in it's simplest terms is a group of individuals (I'll refer to males but you have a similar situation with females) who share the same common ancestor at some point in time and this sharing is defined by having a similar SNP (Single Nucleotide Polymorphism) which is more or less a mutation. In the case of males genetic information for the haplogroup is carried on the y chromosome, as this passes directly from father to son (until a male has no children or only daughters) in an unbroken line.
The following links should give you more info along with a "family tree' of the male haplogroups. The one in question when talking about Ireland is called R1b.
http://en.wikipedia.org/wiki/Haplogroup
http://en.wikipedia.org/wiki/Haplotype
The early studies linking Irish males (also Scottish, Welsh and to a lesser extent English and Norwegian) to Basques really hinged on two things; R1b being dated to around 15,000 years ago and Ireland not having any inwards moving of people since the first inhabitants came in after the ice age ended.
Now haplogroups can be broken down into further subgroups, the easiest way to explain it is that certain markers (as far as I can tell certian locations on the y chromosome) are looked at and it is determined how often the acids in DNA are replcated (this is called STR analysis), if individuals have a similar pattern of replication then more than likely they are more closely related. Early studies looked at something like 6 or 12 markers, to put that in context commercial companies which do tests for individuals offer 37 markers as standard and can go up to 111. That just shows how the science progressed, also more people are getting tested which increases the databases.
The first person to put forward the idea of the similar ancestry was as far as I can tell Stephen Oppenheimer in his book Origins of the British (although I think the National Geographic crowd did aswell). In simple terms the arguement went like this; the region near the current Basque region is thought to have been habitable during the ice age, Basques were always though of as a very old aboriginal population (probably due to their unique language which isn't related to any other known language), Basques have over
90% headcount of R1b, Irish, Scottish and Welsh have anyhting between 70% to 85% so it was very easy to see a link.
As the science progressed the dating was called into question, the link below goes over it. Basically the groups the Basque region and the Isles fall under were thought to be around 6,000 to 8,000 years old (the origin is thought to be somewhere in the lack Sea Caspian Sea area.
http://dienekes.blogspot.com/2010/08/r1b-founder-effect-in-central-and.html
Also more people got tested and R1b was found to be widespread but not as much as the Basque region, ireland etc
Also the idea of Basques being an aboriginal population fell by the way side (Sardinians seem to be the closest to a relic population)
http://www.buildinghistory.org/distantpast/basques.shtml
The graph below shows a family tree of R1b, the main one in Ireland is L21 (bottom right) and the main one for the Basques is M153, so whenever those mutations went their separate way is when the two groups last shared direct male line ancestry, this is thought to be around 6,000 to 8,000 years ago.
http://compsoc.nuigalway.ie/~dubhthach/RTree-2009.JPG
L21 is thought to have originated in North West/Central Europe about 4,000 years ago and made it’s way to Ireland via North France and then Britain. About 8,000 years ago R1b seems to have exploded across Western Europe possibly with the spread of farming. At the bottom right of the screen you’ll see something called M222; this is what they referred to on Blood of the Irish when they talked about a gene linking people with Niall of the Nine Hostages. Around 1,500 or 2,000 years ago a male lineage really took of in Ireland probably due to the social set up of chieftans having many wives. It’s estimated that around 25% of males in the North West of Ireland carry this. It turns up in surnames associated with the UiNiall and UiBrien dynasties and there’s a very good chance it actually originated in North England or Scotland.
It seems with Blood of the Irish they were just unlucky that the science snowballed and they ended up being out of date.
The below link looks at the R1b found in Africa
http://dienekes.blogspot.com/2010/01/r-v88-and-migration-of-chadic-speakers.html
The website below is worth signing up for and browsing through the search function if you have time as I really just gave a brief overview. The whole thing is also a WIP and the science is advancing; about 10 years ago it cost millions to sequence the human genome, in a few years it could be a $1,000 and we mightn’t even have the capability of processing/analyzing the data yet. Anyway big picture wise it seems the population of Ireland is more or less the same as the old celtic iron age invasion idea but happening in the bronze age with some possible military elite invasions in the iron age (like M222 above) and we are more similar with British people genetic wise.
http://dna-forums.org/
Below is a link to a project currently taking place looking at the DNA of local irish populations if you’re interested in taking part.
http://www.docstoc.com/docs/99258621/Irish-DNA-Atlas-Project-Newsletter---Vol-1-No-1
The reason I mentioned the 1930’s study is that they looked only and physical appearance and I think it is a simplistic way of trying to tie populations together, for every irish person you could find that looks like a Basque I’m sure there are many instances of those who don’t or irish people that look like others. One of the reasons I think there is a mystique about dark features in Ireland is that it goes against the typical pasty red head stereotype. I’m sure people in Connemara or Donegal (where I’m from) having to endure working outdoors fishing and farming may have something to do with it. I don’t buy the Armada story as it’s sometimes presented as a couple hundred men spread from Antrim to Cork all of a sudden changed the physical appearance of the Irish, there is a actually a similar story in some Scottish Island where some of the survivors ended up. I’m sure a few may have hung around plus given the fact that Portuguese and Basque fishermen were fishing of the coast of Canada before Columbus reached America you may have had a few encounters.
