Requested improvement: Show autosomal DNA tests on more cousin profiles

+12 votes
237 views

Currently, autosomal DNA test information is propagated, via the "It is likely that these autosomal DNA test-takers will share DNA with..." note as far back as the tester's 6G grandparents and as far laterally the tester's 3rd cousins.

I believe that the algorithm that decides where to show autosomal DNA test information follows essentially the same logic as the algorithm used by Connection Finder. That is, it counts relationship steps along blood connections, and it apparently goes back 8 steps for ancestors and 7 steps for cousins. However, considering the theoretical statistics of DNA sharing, if the algorithm goes back to 6G grandparents, it should go out at least as far as 3C-1R cousins and probably also 4th cousins.

Adding additional degrees of sharing for cousins would make WikiTree's DNA tools more useful for members. I've found some hitherto-unknown 3C-!R and 4th cousins as a result of exploring some good DNA matches, but (for those who are also WikiTree members) WikiTree doesn't show their DNA test information on my profile, nor mine on theirs.

I don't think that autosomal DNA test data should be propagated any farther back than 6G grandparents, where it is now, so I think the improvement I'm asking for might be tricky to implement.

in WikiTree Tech by Ellen Smith G2G Astronaut (1.1m points)
If a filter wasn't also implemented for the cousins, presumably there'd then be too many matches to list.
Ellen, could you have found those 3C1R and 4C matches you mention on the profile(s) of the common ancestors?

Yes, the cousins do show up on ancestral profiles. However, when I go back to ancestral profiles, for example Gardner-3442, the message tells me that the ancestor may share significant DNA with a list of testers. That's interesting, but often some or all of those testers are on a different branch of the family and are too far away from me to share significant DNA with me. That's OK. But  these lists (such as that list) may include 3C1R and 4th cousins with whom I share significant DNA (38 cM on 2 segments, in the case of one 3rd cousin once removed on that Gardner list), and WikiTree doesn't show those connections as people I could possibly share significant DNA with. That's not at all unusual: https://isogg.org/wiki/Cousin_statistics indicates that more than 80% of 3C1Rs and almost 70% of 4th cousins are likely to have autosomal DNA matches.

WikiTree takes pride (for good reason) in its DNA-related tools, but we are missing out on some potential value of those tools by prematurely truncating the display of cousins "likely to share significant autosomal DNA."

I have never found Wikitree's DNA tools the least bit useful (and barely intelligible), so this change is irrelevant to me.
I completely agree with you, Ellen. This is a great idea! I would love this improvement to take place.

3 Answers

+4 votes
Agreed.  DNA helps to confirm the paper trail.  It has also helped to focus research in particular areas to see how I may connect with others.

Laurie
by Laurie Angel G2G5 (5.2k points)
+4 votes
x-DNA matches can extend several generations further than normal autosomal DNA matches. Limiting the potential people with whom we share DNA can make x-DNA cousins  harder to find. Please consider x-DNA when making any assumptions about generations between DNA cousins.
by Bill Vincent G2G6 Pilot (126k points)
+1 vote

You will not share a detectable about of autosomal DNA with about 80% of your 4th cousins: https://customercare.23andme.com/hc/en-us/articles/212170958-DNA-Relatives-Detecting-Relatives-and-Predicting-Relationships#percent_shared

CORRECTION, 4th cousins when they share DNA will share on average about .2% of their DNA.

According to https://www.ncbi.nlm.nih.gov/pubmed/6857549 About 69.3% of 4th cousins will share a detectable amount of autosomal DNA. But how accurate would it be to declare a segment is from a particular shared ancestral couple without triangulation?  It is not uncommon for 4th cousins to share more than one ancestral couple.

Here are simple steps to see all your autosomal DNA matches in WikiTree: https://www.wikitree.com/g2g/948583/who-are-your-dna-matches-in-wikitree

by Peter Roberts G2G6 Pilot (524k points)
edited by Peter Roberts
Peter, that only works if they're on GEDmatch, doesn't it?
It works for all your auDNA matches in WikiTree who have their GEDmatch ID in WikiTree.

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