July 2016
Preface
Because Y Chromosome DNA (Y-DNA) represents such a small part of one’s ancestry, I decided initially not to pursue tests beyond the basic one. However, Family Tree DNA (FTDNA) have some very active groups researching the different Y-DNA haplogroups and they persuaded FTDNA to put together specially tailored tests at special prices. I was emailed by one of the group conveners suggesting I take one for members of the R1b1a2 haplogroup and I decided to go ahead.
Y-DNA
The Y chromosome is only possessed by males, isn’t subject to crossing over and accumulates mutations at a high rate – higher than autosomal but lower than mitochondrial DNA (mtDNA). The mutations allow a paternal time-line to be established, but as with mtDNA, this is not as easy as it at first appeared.
The earliest method of typing Y-DNA looked at sequences of nucleotide pairs and inferred the specific differences due to mutations. The groups obtained by this method were called haplotypes and this was the first test I did. Subsequently it has proved possible to explicitly identify individual nucleotide changes (“single nucleotide polymorphisms,” SNPs for short). In this case the resultant groups are called haplogroups. My most recent results are of the latter type.
All modern humans are thought to have descended from one man “Y chromosomal Adam” who lived 200-300 thousand years ago in Africa and who may not have been a modern human. The main haplogroups have been labelled with a letter of the alphabet and Adam’s is “A.” The evolutionary tree is complicated, much more so than for mtDNA and I haven't tried to reproduce it here.
I initially had a third of my Y-DNA tested and this looked at sequences of nucleotide pairs and inferred the specific differences due to mutations. From this my primary haplogroup is R which is the commonest haplogroup in Eurasia. However, my sub-group (clade) from my initial tests is R1b1a2 which is again common in Europe and very common in the British Isles. 95% of men in Wales belong to this group. There is a good article in wikipedia on haplogroup R1b which contains a tree from A down to R. Bryan Sykes, who first got me interested in this, gave names to some of the haplogroups occurring in the British Isles in his book “The Blood of the Isles” and he christened R1b “Oisín” (Ossian) after an ancient Irish chieftain.
My Y-DNA results apply to all of us with a birth surname of Coombs (plus Gareth). The earliest Coombs I've found so far is Thomas, born about 1773, probably in Corsley, Wiltshire. With lots of daughters in recent generations, the line looks like dying out – maybe the newest Thomas will perpetuate it?
New tests
R1b1a2 is characterised by the mutation R-M269 and this was inferred for me from the sequence tests. FTDNA offered explicit SNP tests so I took those up. The result was a great chain of SNPs for which I am positive and indeed lots for which I am negative. Of particular significance is R-L21 for which I am positive and DF27 for which I am not. I copied the map below from Eupedia where it is clearer, there are lots of figures and data there on Rb1 and its descendants.
R1b originated in modern day northern Iran 20,000 to 27,000 years ago (before present, BP), in the middle of the last ice-age. The people with this mutation migrated west then north across the Caucasus to the Pontic Steppes where M269 appeared around 7,000 BP. These people migrated west to the north of the Black Sea with mutation L23 appearing around 5,000 BP in present day eastern Europe. Our branch moved north west with mutation L11 appearing in the vicinity of modern day Poland around 4,500 BP with a further mutation, P312, in western Germany just over 4,000 BP. There was a general spreading out from there with our branch, L21, moving to the British Isles 4,000 years or so ago and these days, L21 is particularly prevalent in Ireland. Mutations after L21 are “work in progress” through the FTDNA groups and elsewhere. My next significant mutation is R-Z253. FTDNA has groups for this and L21 and I’ve joined both. Below Z253 I am positive for Z2534 and after that A16 which is my “terminal” haplogroup at the moment. From ISOGG the formal hierarchy for this is: R1b1a1a2a1a2c1f2b. There are 4,714 members in the L21 group and 609 members in Z253. In my terminal sub-group there are only 7 of us. Three give a countries of origin which are England, Scotland and Ireland, all with different surnames. Z253 seems to have appeared around 3,000- 4,000 BP and A16 is two mutations further on, so only slightly younger, perhaps around 3,000 BP during the late Bronze Age, and probably in Britain.
Summary
During the last ice-age our distant male-line ancestor lived in what is now Iran. After the ice retreated, his descendants moved across the Caucasus to the Pontic Steppes and then progressively west arriving in Britain between 3 and 4 thousand years ago.