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Ahnentafel Questions (I) (Posted on 2004-04-11) Difficulty: 2 of 5
In genealogy, a pedigree chart, which shows one's direct ancestors (parents, grandparents, etc. but not siblings, cousins, etc.) is often replaced by the equivalent but space-saving Ahnentafel table.

An Ahnentafel table is simply a numbered list of each ancestor, usually on separate lines. The "root" person goes on line 1. Then, for any person on line n, his father goes on line 2n and his mother goes on line 2n+1. Every ancestor gets a unique line, and every line gets a unique ancestor* (mathematically, at least -- in real life Ahnentafels, because a person may not know all of his ancestors some lines may be blank, and in the case where cousins married, their common ancestors may show up in several places in their children's Ahnentafels).

Question 1: Your great-great-grandfather(2nd-great-grandfather) was the first of his name (surname) (which you inherited) to come to America. What is his Ahnentafel number? What is the Ahnentafel number of your nth-great-grandfather of the same name?(Assume the the Western tradition where a child inherits his father's surname)

Question 2: Your Mitochondrial DNA is passed on only from your mother, who got it from her mother,etc. What is the Ahnentafel number of the great-grandmother from whom it "originally" came? Of the nth-great-grandmother?

[Hint: for the general case (nth-great-grandfather in question 1, nth-great-grandmother in question 2) it might be easier to work with m=n+2; m is the number of generations between the ancestor and your children. For n=1 (your great-grandfather), m=3 -- three generations in between: your grandfather, your father, and you.]

*This statement (that there is a one-to-one correspondence between Ahnentafel numbers and the set of all natural numbers) is fairly easy to prove. And, in fact, the proof is part of a later puzzle in this series. For this puzzle, it can simply be assumed.

  Submitted by TomM    
Rating: 2.8333 (6 votes)
Solution: (Hide)
Answer 1: 16

Notice that you are following the all-male ancestor line. Your father is 2, his father is 4, his father is 8, and his father is 16. In general, the Anhentafel number for the nth-great-grandfather is 2^m = 2^(n+2)

Answer 2: 15

Your mother is on line 3 [=2(1)+1]. Her mother, your grandmother, is on line 7 [=2(3)+1]. Her mother, your great-grandmother is on line 15 [=2(7)+1]. In general along the all-female branch, your nth-great-grandmother is on the 2(2(2...+1)+1)+1st line (with m parentheses), which, given the one-to-one we will prove in a later puzzle, simplifies to [2^(m+1)]-1 = [2^(n+3)]-1

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re(6): Thanks heaps! (Chart vs Table/Array)TomM2004-04-24 23:53:40
re(5): Thanks heaps!Richard2004-04-14 15:17:53
re(4): Thanks heaps!e.g.2004-04-14 08:14:26
re(3): Thanks heaps!Richard2004-04-13 13:38:54
re(3): Thanks heaps!Oskar2004-04-13 10:56:00
Some Thoughtsre(2): Thanks heaps!Federico Kereki2004-04-13 09:11:32
re: Thanks heaps!TomM2004-04-12 19:49:09
Some ThoughtsThanks heaps!Federico Kereki2004-04-12 10:10:04
re(3): SolutionPenny2004-04-12 05:32:11
re(2): SolutionTomM2004-04-11 21:02:20
Solutionre: SolutionFederico Kereki2004-04-11 18:16:16
SolutionIs this any better, TomM ?Penny2004-04-11 16:52:48
re: SolutionTomM2004-04-11 12:24:33
SolutionSolutionFederico Kereki2004-04-11 11:41:52
Some Thoughtsquestion 1 (most likely wrong)Billy Bob2004-04-11 11:18:35
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