As we reach n = 21, however,the number of different ancestors in that generation becomes a significant fraction of the entire size of the population.As we go back yet further from here, it is interesting to see how the remaining number of people in that generation that you are not descended from diminishes rapidly.
For example, at n=21 the percentage of the population you are descended from is 36.7 %, which means of course that you are not descended from the other 63.3 %.This means that,in the generation in question,when people were looking around for partners for procreation,prospective partners that you are descended from represent about a third of that population and so will assign themselves in that proportion to those you are not descended from and thus create offspring that you are descended from.
The preceeding generation,therefore (n=22) will thus contain a number of people you are not descended from which is down on the generation n=21 by 36.7 %.By taking the new ratio in generation n=22 between those you are descended from and those you are not,we can then repeat the logic and calculate the figures for n=23, and so on.We can thus complete the Table:
n Number of different ancestors % of population
21 734,733 36.7 %
22 1,199,086 60.1 %
23 1,679,634 83.9 %
24 1,948,741 97.4 %
Here is therefore a Table of monarchs and your chances of being descended from them :
n Epoch Monarch Chance(%) 1 Chance in...
9 1663 Charles II 0.01 10,000
11 1604 James I 0.05 2000
13 1530 Henry VIII 0.2 500
15 1470 Edw IV.,Rich III 1.08 93
17 1399 Rich II., Hen IV 4.2 24
19 1333 Edward III 20.2 5
20 1300 Edward I 31.0 3
22 1233 Henry III 60.0 3 chances in 5
23 1200 John 84.0 5 chances in 6
24 1168 Henry II 97.4 Near certainty.
---- Michael Marshall