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Unique Ancestors - Extended Analysis

Why is this extension required?

As described in the preceding page, I propose a simplified general ancestry model based on recorded information for Prince William. It has been pointed out by a number of contributors to s.g.m. that his ancestry combines specific royal lines, having well understood characteristics including some cousin marriages and a small though widespread genetic base, with a number softer and broader based non-royal lines. My analysis blurs the boundaries of these groups, and so may produce misleading projections when applied to people with differing ethnicities and backgrounds.

Basis of extended analysis

This further analysis examines the eight great grandparents of Prince William. These people are shown in the following table together with details of the number of generations for which ancestors are known to a particular degree.

AT #
Ancestor
Generations for % known
100%
50%
10%
1%
8

Prince Andreas of Greece

9
23
32
39
9

Princess Victoria of Battenburg

5
20
31
39
10

King George VI of England

8
23
32
39
11

Lady Elizabeth Bowes-Lyon (the Queen mother)

5
8
14
24
12

Albert Spencer, Earl Spencer 7th

6
9
16
27
13

Lady Cynthia Hamilton

7
11
19
30
14

Edmund Burke Roche, Baron Fermoy

5
6
8
12
15

Ruth Gill

4
6
9
19

These ancestors fall clearly into two groups. The royals and non-royals. While the first eight or so generations of the royals contain some variable elements, there is clearly a lot of common ancestry beyond that point. I am still amazed that I know 50% of the ancestry of these people at 23 generations. The non-royal group is only fully accounted for in around five generations, with the 50% point coming up in nine generations. Clearly there is a different mix present between these groups as suggested.

For the purpose of my analysis, I have considered the ancestry details to the 10% known point only, as the higher generations show a highly skewed result.

Chart of Forecast Uniques

The Forecast Uniques shown here are projected for each generation based on the details for the knowns. This assumes the same mix applies (a bold assumption). The average curve I previously proposed is also shown for comparison.

The two groups can be clearly seen in the chart, with the limits of the data at the 10% known point. On this basis my projection is biased towards the non-royal side, but obviously it is an average. Without more detailed information on the ancestry of Prince William, the turning point for the non-royal group will be hard to predict.

Conclusion and Request for Information

At this stage I still believe my proposal that we generally have less than 1,000,000 unique ancestors within 80 generations is still feasible, but this needs to be qualified to have consistent ethnic grouping. However, even were this figure to be increased by another order of magnitude to 10,000,000 uniques (an outside chance), this is still miniscule compared to the 1.2E+24 real ancestors to that point.

If anyone has detailed ancestral information in the non-royal area that would complement or contradict my details above, I would be delighted to process the information for them. This is easily done from a GEDCOM file, and of course the details would be treated as confidential.

I continue to hope that these notes provoke some further thought and contributions on this topic.


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Updated 5 February 2006 Copyright Ian D Fettes 2002-2006
 

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