The current y-chromosome markers for the Bassetts of Staffordshire and Cornwall, who share similar results are shown below. In a joint project to find out more about these Bassetts and to see if they do indeed share a common ancestor, we did some further DNA testing on six of the kits.
Latest Developments in DNA Testing by Neville Bassett
Until now we have all been using STR (Short Tandem Repeat) markers to piece together our family histories. In some cases this has proven definitive, but in many cases there are still tantalising links that have not been established, or complete brick walls that seem unscaleable. Very few participants have used SNP tests (Single-Nucleotide Polymorphism, pronounced “snip”). In part this is because in the past many SNP tests have only been able to suggest broad trends in population genetics. For example in June 2007 we reported a SNP test from the #2B Thomas Bassett of Virginia family which indicated this family originated in the Balkans in Eastern Europe. Their SNP (I1b) dated from the Last Glacial Maximum some 20,000 years ago.
However there has been much work done in the last few years tracing the human tree from “Adam” down though all its various branches to the present day. New SNPs are being discovered monthly. For example, back in 2006 there were only 17 SNPs known within the R1b haplogroup. The current ISOGG tree now has 148 SNPs “downstream” from R1b, serving to subdivide the haplogroup into ever more well-defined “clades”. Best of all, the dates of the mutations defining some of these SNPs are moving into the timeframe of most interest to genealogists, the period when surnames began to be adopted.
SNPs also have an advantage compared to STR mutations, in that SNP mutations are basically “for ever”. STR marker values can however increase or decrease with each “transmission event”. Over time this can mean that two participants might end up with very similar STR values whereas their awfully-great-grandparents had less similar values. (Imagine two people standing in the Arrivals Hall at Union Station Los Angeles. STRs can only tell you that they have arrived at the same place, but SNPs are like their train tickets which tell you that one person came from New York, but the other travelled from Seattle).
This month we can report a case which illustrates the effective use of SNPs. The Bassetts of Cornwall (lines 149B, 52B, 44B and 177B) have been known for several years to have similar STR values to the Bassetts of Staffordshire (lines 33B and 263B) and possibly to Thomas Bassett of Connecticut (line 3B). It was suspected that there was a connection several hundred years ago, but with no paper trail. Keith Bassett (#2851) and his brother Neville decided to test this connection using SNPs. Firstly Keith’s “terminal SNP” was determined, by means of a “Deep Clade” test from FTDNA (which gave a result of P312+), followed by two tests of individual SNPs (which showed Keith to be DF19+ and L644+). As there are no SNPs known at this stage to be downstream from L644, this is Keith’s terminal SNP. A current diagram of the R1b-P312 tree can be seen at http://www.familytreedna.com/public/atlantic-r1b1c/default.aspx?section=results .
Having established the terminal SNP, it then became feasible to prove or disprove links to other family lines at relatively low cost ($39 per SNP). These tests showed that the Bassetts of Redruth (#2851), St Enoder (#7007) and Helston (#77522) in Cornwall all had the same positive terminal SNP L644. (The Bassetts of Lanreath (# 3034 would very likely share the L644 SNP). They were however unrelated to the other family lines in Staffordshire and Connecticut.
The L644 SNP is of particular interest for three reasons. It is a fairly rare SNP, with only 13 family names out of about 2,000 in the R1b-P312 Project known or suspected to be positive for it. It is a very recent SNP. Wim Verelst (Co-administrator of that Project) has suggested that the mutation that defines it first appeared between 760AD and 960AD (although the timing may change as more results come through). Further, Wim suggests that the SNP appears to have developed in northern Germany or Denmark, but then travelled to the British Isles. The timing suggests that it could not have been involved in the Anglo-Saxon invasions of England, but is more likely to have come via the Norman Conquest.
Having proven the relatedness of the Cornwall Bassetts by the L644 SNP tests, more value can then be extracted from the earlier STR results. In particular, it is interesting that kits #2851 and #77522 share a common ancestor despite a mismatch of 5 markers out of 37. The STR mutation rate was calculated for the Cornwall Bassett family through three well-documented St Enoder lines. On average, one STR mutation was found to occur (out of 37 markers) for every ten “transmission events” (that is, every 5 generations). For the two Redruth lines, the mutation rate was zero over 7 generations, but this may reflect a mutation followed by a back-mutation. Other families which are L644+ have one STR mutation every 10 to 11 transmission events (5 or so generations). This suggests that the Most Recent Common Ancestor of kits #2851 and #77522 lived 20 to 25 generations ago and had the name Bassett/Basset. This estimate can be improved if more kits are upgraded to 67 rather than 37 markers.
The earliest Bassett known to have lived in Cornwall was a descendant of Osmund Basset (first noted in 1117, 25 generations ago), who founded the family of the Bassets of Tehidy. Osmund Basset appears to be from a Norman family with an estate at Montreuil-au-Houlme in Normandy, but there is no direct evidence of his parentage. The rarity of the L644 SNP, its young age (and hence its apparent arrival in England with the Norman Conquest), and the age of the common ancestor for the Cornwall Bassetts provide strong evidence that the Cornwall Bassetts are descended from the Bassets of Tehidy.
SNP testing can be seen to have been a cost-effective way of proving and disproving links. Although we do not know the terminal SNP of the Staffordshire Bassetts, we do know it is not L644, and they are therefore unrelated to the Cornwall Bassetts within historical times. Similarly we do know the terminal SNP of the Bassetts of Bodiam (L2+), so they too are not related to the Cornwall Bassetts either (although they may be related to the Staffordshire Bassetts.
Although STR testing can give ambiguous results, it provides the best guide as to which SNPs to test for. The final decision to try L644 as the terminal SNP was based on the fact that an “STR motif” of DYS385b=15 and DYS481=23 is a strong guide for a positive L644 result (but only for those who are P312+). As DYS481 only appears in the 67-marker STR test, it is very helpful to have STR tests done to 67 markers rather than 37. Having 67 markers also greatly improves the accuracy of calculations of the Time to Most Common Recent Ancestor.