Accuracy of Genealogy Data
Food for Thought
Studies have been done on Bluebirds and it was found that the hatchlings in the nest were sired by males other then the male who seemed to be the one associated with that nest. The results showed that only about 2/3 of those in the nest had the male that was assumed. Follow-up studies on other birds and humans found similar results. With humans, it was found that many factors were present and socio-economic level was one factor. Based on this finding, if one takes a genealogy tree that has up to 10-generations and determines the percentage of accuracy of any generation with different levels of probability that the offspring had the same father then one comes up with the results shown in the following chart.
Most people who do genealogy assume that the father of the household was the father of the children but only DNA testing can prove this to be true. The values in the chart, shown below, left column shows the probability that the father is the Head-of-household and the top row shows the Generation level. The values in each cell give the accuracy of the results of that person being the one that normal genealogy research would find as being the parent of that child.
Generation
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
|
|
70% |
70% |
49% |
34% |
24% |
17% |
12% |
8% |
6% |
4% |
3% |
|
75% |
75% |
56% |
42% |
32% |
24% |
18% |
13% |
10% |
8% |
6% |
|
80% |
80% |
64% |
51% |
41% |
33% |
26% |
21% |
17% |
13% |
11% |
|
85% |
85% |
72% |
61% |
52% |
44% |
38% |
32% |
27% |
23% |
20% |
|
90% |
90% |
81% |
73% |
66% |
59% |
53% |
48% |
43% |
39% |
35% |
|
95% |
95% |
90% |
86% |
81% |
77% |
74% |
70% |
66% |
63% |
60% |
|
100% |
100% |
100% |
100% |
100% |
100% |
100% |
100% |
100% |
100% |
100% |
Probability of father of child being the same as the male-head-of household vs. generation level of chart.
As can be seen by the results shown in the cells, accuracy values of less then 80% are the dominant values and leads one to question the value of doing family trees beyond 2-3 generations unless other means are used to improve the accuracy of determining the father of the child. This is where DNA testing results can add additional information to assist in proving that one has the correct relationships in any family unit. This analysis is similar to the case where a child could be adopted with no documentation to show the parentage and the researcher just follows the family line blindly without proof that the child is truly of those parents. I don't want to be alarmist about this but it is a factor that makes one question the accuracy of multi-generation family trees unless extreme care has been taken to ensure accurate data.
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since 8 Mar. 2005