JULIAN LAND'S USE OF AUTOSOMAL DNA WITH REMOTELY-CONNECTED FAMILY BRANCHES

 

The relationships we sought to prove are distant enough to severely test autosomal DNA. The potential link between for example the Barrows and Lousadas and their 10th and 11th cousins among the USA Lousadas goes back 9 generations to different siblings of Amador de Lousada of Vinhais. Even 4th cousins do not show up well, for Julian has only one (25cM) segment in common with his 4th cousin Jeremy Lousada, and only 3 3cM matches with his 6th cousin John Griffiths. From the outset, we were well aware of the poor family connection abilities of conventional small (3cM) segment matches. To combat this, we sought to rely on maximising the number of matches and then using statistical and related techniques to discern patterns lying within our datasets. We used a 13-relative sample across 4 branches - MD (English Lousadas), Ju A and J (Barrow-Lousadas), JG E RF RM and SW (Barrows), and ELL B Je and TP (USA Lousadas). For comparison we used a set of 13 random people (but we checked how random they turned out to be).

 

INTRODUCTION - USING QMATCH AT 3CM AND P=3 MADE THE RELATIVES INVISIBLE!

 

As Qmatch was recommended to us for small matches by GEDmatch, and retaining our desire to accumulate many matches, we set about using Qmatch (set at 3cM, P=3) to compile all 2255 segment matches from our 13 relative sample - see here the 1963 matches found before ELL was added to the sample of relatives. It was fascinating to ponder in this data the 46 Rare Segment Boundary Coincidences (RSBCs), 25 lefthand and 21 righthand. We spent much time looking at RSBCs, how frequently they occur across chromosomes and in the match-rich areas on chromosomes. But they proved quite difficult to work with, and were relatively unproductive.

 Our attention then shifted to Abutting Segment Boundaries (ASBs) but they also proved misleading and just as we prematurely claimed in  'Fun with Autosomal DNA', we again thought that we may have established a genetic link between the USA Lousadas, the English Lousadas, the Barrows, Scott's wife (and hence the Fischls) and Randy's parents. The problem with ASBs was that instead of an ASB being associated with a unique crossover, in fact many unrelated crossovers can all report to the same ASB (in fact the same also applies to RSBCs). This is because the true position of a crossover lies between 2 SNPs - these SNPs being the first non-matching SNP beyond the crossover at one end of a segment and last SNP within the segment at the other end of the segment. Thus the 2 crossovers are each assigned the position of one of those 2 SNPs. Typically there are 5000 base-pair positions between each SNP so the potential for unrelated and (from the family viewpoint) spurious crossovers at the same ASB is large. That is, ASBs are not the amazingly precise way of penetrating the fog of unreliable small matches that was hoped.

From Chart 1 we belatedly realised the futility of the 3cM P=3 results. For at this setting the randoms show more segment-matches than the relatives - 2261 to 2255 - that is, family does not show a signal! While the RSBC totals indicate that a family signal may exist, the ASB numbers seem odd (and perhaps can only be explained by a combination of spurious crossovers and the much greater possible ancestor pool where there is no genealogy). In the next section we look at P=7, but our first look at P=7 came (as shown in Chart 1) with the 2 3pASBs for relatives suggesting an A/Je connection (on Cr3), and a JG/B connection (on Cr17), while hoping that the common relative in each participating pair may increases the value of 3pASBs (compared with 4pASBs). The four 4pRSBCs for relatives compares with 1 4pRSBC among the randoms. However, strictly, neither of these ASB or RSBC signals is useful, because for the reason set forth earlier, no genuine crossover can be precisely located.

 

 CHART 1- COMPARISON DATA RELATIVES AND RANDOMS

 

 

USING GEDMATCH AT 3cM AND P=7 MADE THE RELATIVES STAND OUT (AT LAST)

 

From this impasse it was timely advice from GEDmatch in February 2026 which rescued us. Thus, we came to use Qmatch to look again at all 3cM segment-matches, not at P=3 but at P=7. These conditions of course give reasonable quality segment-matches, almost as good as 7cM matches from some other providers. And most importantly Chart 1 shows that at 3cM P=7, the relatives show 560 segment-matches which is 187 more than the randoms' 373 segment-matches, the strongest such family signal we have seen in all our many comparisons of a set of relatives with a set of randoms. Our analysis focuses on extracting information from this signal, after we considered the signal arising from the 7cM matches, and also from the 5cM matches (for the latter matches are comparable to 7cM matches from other providers).

In Chart 2, we see represented all the segment-matches from the 13 relatives, noting that the 560 segment-matches show as 1120 because in this chart each pair of relatives is counted twice. Yellow is used to indicate the presence in a relative pair of at least one 7cM segment-match and likewise green for 5cM. Many interesting features are present. For example, among the 14 B/Je segment-matches is one of 5cM on Cr10 which is presumably their Ancestry.com 7cM match. Notably, JG misses matching (shown in grey) 2 of the Barrow-Lousadas (A and J) but not Ju who nevertheless also shows a weak match ultimately because of JG's specific ancestry.

Before we interpret the 5 & 7cM segment-matches, we remind ourselves that there are 4 branches of relatives - English Lousada (MD), Barrow-Lousada (Ju, A, J), Barrow (E, JG, RM, RM, SW), and US Lousada (ELL, B, Je, TP). The Barrow-Lousada branch has the highest level of Lousada genes. This arises because, though both the Barrows and the US Lousadas descending from Moses #54 (B, Je, TP) likely double their inherited quota of Lousada genes through consanguinity, the Barrow-Lousadas add to similar consanguinity by way of their Barrow marriages (there are 2 such marriages in the case of Ju and A and 1 for J). The sole English Lousada does not have a Barrow marriage nor Lousada consanguinity.

We can now attribute the 5 & 7cM (green and yellow) matches in Chart 3 and 5 between the Barrow-Lousadas and the US Lousadas to their joint Lousada ancestry. We cannot do the same with the Barrow matches shown by the Barrow-Lousadas, because the Barrows carry non-Lousada ancestry (Pressburg, perhaps Lichtenstadt, Montefiore, Nunes and Goldsmid) which is therefore also present in the Barrow-Lousadas to varying degrees due to the above-mentioned marriage(s). But the Barrows also have matches with the US Lousadas, the lower number presumably attributable to their reduced Lousada genetic inheritance. The more modest English Lousada matches with the other 3 branches presumably reflect a low and unenhanced Lousada genetic inheritance. Finally the Barrow matches with the US Lousadas are supported by triangulations (led by E/B/Je) as discussed below.

 

  

CHART 2 - RELATIVES SEGMENT-MATCHES

 

 

COMPARISON OF RELATIVES AND RANDOMS 

 

A comparison set of 13 random people was studied and a summary of their segment-matches is set out in Chart 4. The presence of 5cM and 7cM segment-matches in Chart 4 is indicated by the same colours as in Chart 2.

We were able to discern obvious differences - not only (as noted above) the total number of segment-matches differs (373 for the randoms cf 560 for the relatives) but also the number of misses, the distribution of high-matchers and low-matchers, the number of triangulations, and the general intensity of matching within the 2 sets:

As there is only 1 English Lousada we can only consider 3 not 4 groupings for intrabranch matching. We can see in Chart 3 that the intrabranch matching within each of the 3 groupings exceeds that of the random set. Of course boosting the relatives' intrabranch matching are the close family links revealed by the triangulation shown by the 1st and 4th cousins A, Ju and J at Cr16 (3219600 - 6259081) within the Barrow-Lousadas, and the B/Je/TP triangulation among the US Lousadas at Cr2 (217m - 220m). Also the Barrow intrabranch relatives combine the RF/RM/SW sub-grouping from an Ashkenasi milieu with E/JG external to it.

But we can also see that the relatives' interbranch matching exceeds random 5.9 to 4.8. However in the next section we see in the randoms' set an obvious cluster of 5 inter-related people - comprising 154 segment-matches or 15.4 segment-matches per pair for 10 pairs. (This is probably Ashkenasi, and compares with the RF/RM/SW sub-grouping within the Barrows - averaging 21.3 segment-matches per pair). The remaining randoms' 219 segment-matches average only 3.2 per pair of people cf 4.8 - showing that the 5-person structure within the randoms' set partially masks the contrast between interbranch relatives and the randoms.

 Lousada common ancestry appears to be causing enhanced interbranch matching.

 

 

CHART 3 - INTRABRANCH AND INTERBRANCH MATCHING

 

 

ANALYSIS OF RANDOMS 

 

The random set could contain its own (but unexpected/unknown) internal family links which must be allowed for when we consider the real segment-match count and the false (off-target) segment-match count. Chart 4 shows the random set does indeed have structure with several obvious groupings. The central grouping seems to reflect several (perhaps 3) Ashkenasi families variously linked perhaps 4-8 generations ago. A second grouping is more distantly related perhaps with more diverse ancestry. The outer grouping is only remotely related. As we saw above, without the central grouping, the average segment-match count per pair as shown in Chart 3 would be much lower and the relative/random contrast higher.

We can make a rough estimate of the number of real segment-matches among the 373 in the random set. By 'real' we simply mean regarding the central group's 154 segment-matches as equivalent to the relatives' intragroup segment-matches in Chart 2 & 4. That is we regard then all as real, leaving 219 false segment-matches. The estimate depends upon the false segment-matches arising from the 10 pairs in the central grouping balancing the real segment-matches arising in the 68 pairs in the outer groupings, something which is admittedly not proven but something which we have judged reasonable (but with an error estimate - all as illustrated here). 

 

CHART 4 - RANDOMS SEGMENT-MATCHES

 

 

IMPLICATION FOR RELATIVES 

 

Now we must find how the relatives generate 219 false segment-matches. An easy way of doing this is shown here from which we see that deleting all white and green pairs except those showing 9 or more segment-matches is indicated (though a figure of 8 is perhaps not totally out of the question). We note that we now have a probability estimate covering the false segment-matches (namely 39% or 219/560), so that a pair with 9 segment-matches is tantamount to a proven match since 0.39**9 = 0.0002 or 0.02%. Accordingly, we can now present in Chart 5 our estimate of real relative matching. Here the yellow, green and blue colours show matches between relatives. The blue entries show 9-segment matches as just discussed. The yellows have been reduced by ignoring the A/TP 7cM match (but it probably should be reinstated - see triangulation discussion below).

 

CHART 5  - RELATIVES REAL MATCHES

 

 

INTERBRANCH CONNECTION 

 

There are 4 branches of relatives - English Lousada (MD), Barrow-Lousada (Ju, A, J), Barrow (E, JG, RM, RM, SW), and US Lousada (ELL, B, Je, TP). We extract from Chart 5 the number of matching relative-pairs for each of the 6 interbranch intersections, and express this as a percentage of total possible relative-pairs - see Chart 6. From this we can make some observations:

 

These observations are instructive - for they show that aggregation of 3cM segment-matches even at P=7 is not precisely correlated with Lousada genetic inheritance. The effects of small sample size are evident. Nevertheless, the interbranch picture is promising. To strengthen our conclusions we consider next what triangulations can tell us.

 

 

 

CHART 6 - EXTENT OF INTERBRANCH CONNECTIONS

 

 

TRIANGULATIONS 

 

We find 9 triangulations among the relatives at 3cM P=7 - namely Ju/RM/Je and RM/TP/Je and B/Je/TP and Ju/Je/B on Cr2 (217m - 220m), B/Je/E on Cr5 (79m - 81m), J/TP/E on Cr10 (116m - 119m), Ju/J/A on Cr 16 (3m-6m), A/E/RM on Cr17 (31m - 33m), and RM/B/Je on Cr22 (25640628 - 26225384).

Of these Ju/A/J is an acceptable intrabranch triangulation by any measure. B/Je/TP is a strong intrabranch triangulation, having all 3 links from 9-segment pairs (see Chart 5), and is useful confirmation of family relationship within the US Lousadas; it also has other significance as discussed below. The B/Je/E triangulation at Cr5 (79m - 81m) is a strong interbranch triangulation having all 3 links from 9-segment pairs (see Chart 5)..

Before we consider the residual 6 triangulations, we note that the absence of a triangulation can be informative. Thus on Cr18 (6.6m - 8.1m) each of the 1st cousins Ju and A has a 7cM match with TP but don't match each other here at P=7 but share 6.1cM at P=5, which suggests another triangulation. Something similar happened at the triangulations at Cr2 - where Ju/TP and B/RM do not match at P=7 which casts doubt on the Ju/RM/Je, RM/TP/Je and Ju/Je/B triangulations. While we see no sign that there is a RM/B match here, inspection reveals that Ju/TP are close to a match. Accordingly, Ju/B/Je/TP looks like a 4-person triangulation (showing both an intrabranch and an interbranch triangulation), while RM/Ju/Je and RM/TP/Je appear to be false.

J/TP/E on Cr10 (116m - 119m), A/E/RM on Cr17 (31m - 33m), Ju/A/TP on Cr18 and RM/B/Je on Cr22 (25640628 - 26225384) remain. Apart from the A/E/RM triangulation they are interbranch. The meaning of the A/E/RM triangulation is complicated by the 1st Barrow & Lousada marriage. Genealogy does not show RM with Pressburg or Goldsmid ancestry while almost certainly RM does not have Montefiore or Nunes ancestry. The A/E/RM triangulation is therefore evidence of RM's Lichtenstadt but not necessarily Lousada ancestry; though the RM/B/Je triangulation on Cr22 does provide evidence of this. Therefore RM probably descended from the Lichtenstadt & Lousada marriage. So must have E, given his known Lichtenstadt ancestry and the Cr5 and Cr10 triangulations proving his Lousada ancestry. Thus, the interbranch triangulations on Cr2, Cr5, Cr10, Cr17, Cr18 and Cr22 provide evidence of the relatives' branches all being Lousada.

 

CONCLUSION 

We may feel confident that despite the small segment sizes and remote ancestral connection, the evident interbranch matching supports our genealogy (in which the various branches originate in the ancestral family of Amador de Lousada). Importantly, there are few if any contra-indications. Thus while Ju/RF may reflect shared non-Lousada ancestry, RF/B and RF/Je (see Chart 5) indicate that RF also shows Lousada ancestry. And, while SW/Ju and SW/A may also reflect shared non-Lousada ancestry SW/Je (see Chart 5) reassures us as to her also having Lousada ancestry.

 

FOOTNOTE 

Finally, out of respect to those whose kit numbers went into generating the random sample, we comment further on Chart 4. This shows perhaps 3 family linkages around 4-8 generations ago (A/H/J/MW/DG) with a secondary group (N/S/M/P), together with an outlying group (C, MB, MMC, KB). The central 'family' group of 5 contains kits contributed from John Griffiths (A, H, J) and Julian Land (MW, DG). The secondary group of 4 consists of N contributed by John Griffiths and S, M, P contributed by Julian Land. The remotely-connected group of 4 consists of C contributed by John Griffiths and MB, MMC and KB contributed by Julian Land. The set of 13 randoms produced only 2 triangulations, on Cr1 at 158m - 160m (H, S, J) and on Cr8 at 11.3m - 12.6m (S, P, M). At least one of these is probably false - that on Cr1 where S is linked to the central grouping (H and J) - as S has no evident trace of Jewish ancestry.