Timeline for How likely is a lack of DNA match with a distant relative?
Current License: CC BY-SA 4.0
12 events
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| Apr 14, 2021 at 20:27 | comment | added | MikeyC | @jamesqf - That's correct, but I was speaking within the context of the original question, which is about sharing DNA with a contemporaneous relative (i.e. someone with whom at lease one common ancestor is shared). This point is better illustrated in the second figure. Even though there's a high probability of both individuals having at least some DNA from the same common ancestor after 6 generations, it much less likely that they will share any DNA with eachother (~20%). | |
| Apr 14, 2021 at 3:40 | comment | added | jamesqf | @MikeyC: Perhaps I'm misinterpreting the first graph? It seems to show the probability of sharing some DNA with an ancestor 6 generations back as close to 1.0. | |
| Apr 13, 2021 at 21:43 | comment | added | MikeyC | @jamesqf - In this particular context, that wouldn't really be a question of biology, per se, nor would it necessarily be the most probable explanation. Two people with a single shared ancestor 6 generations back would only have about 1 in 5 chances of sharing any common ancestral DNA (yes, that's assuming no misattributed paternity or maternity). | |
| Apr 13, 2021 at 17:49 | comment | added | jamesqf | This doesn't seem to account for the most probable explanation: what we might politely call "misattributed paternity". (IOW, "Your father's not your father".) While estimates of the rate vary widely, 10% seems about average from a quick search. If I'm doing the math correctly, that means that in 6 generations it's about 50-50 that there's at least one such event. | |
| Apr 13, 2021 at 15:10 | comment | added | MikeyC | @BenCrowell - According to the Coop Lab website, these calculations do seem to apply universally (at least with respect to autosomal inheritance), and are not limited to region-specific analyses. I've updated the references to link to the source page for both figures in the answer. Dr. Coop does a pretty good job of walking through these calculations and providing primary references to backup any claims. He has a number of other posts on the topic of genetic genealogy as well. | |
| Apr 13, 2021 at 15:03 | history | edited | MikeyC | CC BY-SA 4.0 |
Updated references to images in post, corrected a misspelled name.
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| Apr 13, 2021 at 13:28 | comment | added | user4617 | It seems to me that this answer is presented in a way that inappropriately suggests that there is something universal about these graphs. If I'm understanding correctly, then the results shown on these graphs depend entirely on which regions of the genome are used. | |
| Apr 13, 2021 at 10:38 | comment | added | Strawberry | you have roughly 1,024 ancestors well, you definitely don't have more; you might have less. | |
| Apr 13, 2021 at 8:01 | vote | accept | carsten | ||
| Apr 12, 2021 at 21:51 | comment | added | JimmyJames | Nice answer. Another factor that might be significant is that there might be parallel relationships that I'm not sure have a specific term in English. That is, siblings who each couple with other siblings. For example, two brothers who marry two sisters. The children of these couplings then are cousins on both sides. This situation is probably was probably rather common in times when families were large, communities were mostly small and transportation was limited. | |
| Apr 12, 2021 at 18:13 | history | edited | MikeyC | CC BY-SA 4.0 |
added 537 characters in body
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| Apr 12, 2021 at 17:59 | history | answered | MikeyC | CC BY-SA 4.0 |