Ahnentafel


An ahnentafel or ahnenreihe is a genealogical numbering system for listing a person's direct ancestors in a fixed sequence of ascent. The subject of the ahnentafel is listed as, the subject's father as and the mother as, the paternal grandparents as and and the maternal grandparents as and, and so on, back through the generations. Apart from, who can be male or female, all even-numbered persons are male, and all odd-numbered persons are female. In this schema, the number of any person's father is double the person's number, and a person's mother is double the person's number plus one. Using this definition of numeration, one can derive some basic information about individuals who are listed without additional research.
This construct displays a person's genealogy compactly, without the need for a diagram such as a family tree. It is particularly useful in situations where one may be restricted to presenting a genealogy in plain text, for example, in e-mails or newsgroup articles. In effect, an ahnentafel is a method for storing a binary tree in an array by listing the nodes in level-order.
The ahnentafel system of numeration is also known as: the Eytzinger Method, for Michaël Eytzinger, the Austrian-born historian who first published the principles of the system in 1590; the Sosa Method, named for Jerónimo de Sosa, the Spanish genealogist who popularized the numbering system in his work Noticia de la gran casa de los marqueses de Villafranca in 1676; and the Sosa–Stradonitz Method, for Stephan Kekulé von Stradonitz, the genealogist and son of Friedrich August Kekulé, who published his interpretation of Sosa's method in his Ahnentafel-atlas in 1898.
"Ahnentafel" is a loan word from the German language, and its German equivalents are Ahnenreihe and Ahnenliste. An ahnentafel list is sometimes called a "Kekulé" after Stephan Kekulé von Stradonitz. A variant of is known in French as Seize Quartiers.

Inductive reckoning

To find out what someone's number would be without compiling a list, one must first trace how they relate back to the subject or person of interest, meaning one records that someone is the subject's father's mother's mother's father's father's ... Once one has done that, one can use two methods.

First method

Use the definition that a father's number will be twice that individual's number, or a mother's will be twice plus one, and just multiply and add 1 accordingly. For instance, someone can find out what number Sophia of Hanover would be on an ahnentafel of Peter Phillips. She is Phillips's mother's mother's father's father's father's mother's father's father's father's father's father's mother. So, we multiply and add:
Thus, if we were to make an ahnentafel for Peter Phillips, Electress Sophia would be #7233.

Second method

1. Write down the digit "1", which represents the subject, then from left to right write "0" for each father and "1" for each mother in the relation, ending with the ancestor of interest. The result will be the binary representation of the ancestor's ahnentafel number. Using the Sophia example:
2. Convert the ahnentafel number from its binary to its decimal form.

Deductive reckoning

We can also work in reverse to find what the relation is from the number.

Reverse first method

  1. One starts out by seeing if the number is odd or even.
  2. If it is odd, the last part of the relation is "mother," so subtract 1 and divide by 2.
  3. If it is even, the last part is "father," and one divides by 2.
  4. Repeat steps 2–3, and build back from the last word.
  5. Once one gets to 1, one is done.
On an ahnentafel of Prince William, John Wark is number 116. We follow the steps:
116/2 = 5858/2 = 2929 − 1 = 28 and 28/2 = 1414/2 = 77 − 1 = 6 and 6/2 = 33 − 1 = 2 and 2/2 = 1
fatherfathermotherfathermothermother

We reverse that, and we get that #116, John Wark, is Prince William's mother's mother's father's mother's father's father.

Reverse second method

1. Convert the ahnentafel number from decimal to binary.
2. Replace the leftmost "1" with the subject's name and replace each following "0" and "1" with "father" and "mother" respectively.
decimalbinaryrelation
11proband
210father
311mother
4100paternal grandfather
5101paternal grandmother
6110maternal grandfather
7111maternal grandmother
81000father's father's father
91001father's father's mother
101010father's mother's father
111011father's mother's mother
121100mother's father's father
131101mother's father's mother
141110mother's mother's father
151111mother's mother's mother

Calculation of the generation number

The generation number can be calculated as the logarithm to base 2 of the ahnentafel number, and rounding down to a full integer by truncating decimal digits.
For example, the number 38 is between 25=32 and 26=64, so log2 is between 5 and 6. This means that ancestor no.38 belongs to generation five, and was a great-great-great-grandparent of the reference person who is no.1.

Example

The example, shown below, is an ahnentafel of Prince William, Duke of Cambridge, listing all of his ancestors up to his fourth great-grandparents.
  1. Prince William, Duke of Cambridge
  2. Charles, Prince of Wales
  3. Diana, Princess of Wales
  4. Prince Philip, Duke of Edinburgh
  5. Elizabeth II, Queen of the United Kingdom et al.
  6. Edward Spencer, 8th Earl Spencer
  7. Frances Roche
  8. Prince Andrew of Greece and Denmark
  9. Princess Alice of Battenberg
  10. George VI, King of the United Kingdom et al.
  11. Queen Elizabeth, the Queen Mother
  12. Albert Spencer, 7th Earl Spencer
  13. Cynthia Hamilton
  14. Maurice Roche, 4th Baron Fermoy
  15. Ruth Gill
  16. George I, King of the Hellenes
  17. Grand Duchess Olga Konstantinovna of Russia
  18. Prince Louis of Battenberg, later Louis Mountbatten, 1st Marquess of Milford Haven
  19. Princess Victoria of Hesse and by Rhine
  20. George V, King of the United Kingdom
  21. Mary of Teck
  22. Claude Bowes-Lyon, 14th Earl of Strathmore and Kinghorne
  23. Cecilia Cavendish-Bentinck
  24. Charles Robert Spencer, 6th Earl Spencer
  25. Margaret Baring
  26. James Hamilton, 3rd Duke of Abercorn
  27. Rosalind Bingham
  28. James Roche, 3rd Baron Fermoy
  29. Frances Work
  30. Colonel William Smith Gill
  31. Ruth Littlejohn
  32. Christian IX, King of Denmark
  33. Princess Louise of Hesse-Kassel
  34. Grand Duke Konstantin Nikolayevich of Russia
  35. Grand Duchess Aleksandra Iosifovna of Russia
  36. Prince Alexander of Hesse and by Rhine
  37. Julia von Hauke
  38. Ludwig IV, Grand Duke of Hesse and by Rhine
  39. The Princess Alice
  40. Edward VII, King of the United Kingdom
  41. Princess Alexandra of Denmark
  42. Prince Francis, Duke of Teck
  43. Princess Mary Adelaide of Cambridge
  44. Claude Bowes-Lyon, 13th Earl of Strathmore and Kinghorne
  45. Frances Bowes-Lyon, Countess of Strathmore and Kinghorne
  46. Revd Charles Cavendish-Bentinck
  47. Louisa Cavendish-Bentinck
  48. Frederick Spencer, 4th Earl Spencer
  49. Adelaide Spencer, Countess Spencer
  50. Edward Baring, 1st Baron Revelstoke
  51. Louisa Baring, Baroness Revelstoke
  52. James Hamilton, 2nd Duke of Abercorn
  53. Mary Curzon-Howe
  54. Charles Bingham, 4th Earl of Lucan
  55. Cecilia Bingham, Countess of Lucan
  56. Edmond Roche, 1st Baron Fermoy
  57. Elizabeth Roche, Baroness Fermoy
  58. Frank Work
  59. Ellen Wood
  60. Alexander Ogston Gill
  61. Barbara Smith Marr
  62. David Littlejohn
  63. Jane Crombie
  64. Friedrich Wilhelm, Duke of Schleswig-Holstein-Sonderburg-Glücksburg
  65. Princess Louise Caroline of Hesse-Kassel
  66. Landgrave Wilhelm of Hesse-Kassel
  67. Princess Louise Charlotte of Denmark
  68. Nicholas I, Tsar of all the Russias
  69. Aleksandra Feodorovna, Empress of Russia
  70. Joseph, Duke of Saxe-Altenburg
  71. Duchess Amelia of Württemberg
  72. Ludwig II, Grand Duke of Hesse and by Rhine
  73. Princess Wilhelmine of Baden
  74. Count Moritz von Hauke
  75. Countess Moritz von Hauke
  76. Prince Karl of Hesse and by Rhine
  77. Princess Elizabeth of Prussia
  78. Albert, Prince Consort
  79. Queen Victoria
  80. = 78
  81. = 79
  82. = 32
  83. = 33
  84. Duke Alexander of Württemberg
  85. Countess Claudine Rhédey von Kis-Rhéde
  86. Prince Adolphus, Duke of Cambridge
  87. Princess Augusta of Hesse-Kassel
  88. Thomas George Bowes-Lyon, Lord Glamis
  89. Charlotte Grimstead
  90. Oswald Smith
  91. Henrietta Hodgson
  92. Lord Charles Bentinck
  93. Anne Wellesley
  94. Edwyn Burnaby
  95. Anne Salisbury
  96. George Spencer, 2nd Earl Spencer
  97. Lavinia Bingham
  98. Sir Horace Seymour
  99. Elizabeth Palk
  100. Henry Baring
  101. Cecilia Windham
  102. John Crocker Bulteel
  103. Elizabeth Grey
  104. James Hamilton, 1st Duke of Abercorn
  105. Louisa Russell
  106. Richard Curzon-Howe, 1st Earl Howe
  107. Anne Gore
  108. George Bingham, 3rd Earl of Lucan
  109. Anne Bingham, Countess of Lucan née Lady Anne Brudenell
  110. Charles Gordon-Lennox, 5th Duke of Richmond
  111. Caroline Paget
  112. Edward Roche
  113. Margaret Curtain
  114. James Boothby
  115. Charlotte Cunningham
  116. John Wark
  117. Sarah Duncan Boude
  118. John Wood
  119. Eleanor Strong
  120. David Gill
  121. Sarah Ogston
  122. William Smith Marr
  123. Helen Bean
  124. William Littlejohn
  125. Janet Bentley
  126. James Crombie
  127. Katharine Forbes
The same information in a tree:

Multiple numbers for the same person

An ancestor may have two or more numbers due to pedigree collapse. For example in the above Ahnentafel for Prince William, Queen Victoria is both no.79 and no.81. She is no.79 because she was the great-great-grandmother of William's grandfather Prince Philip, and she is also no.81 because she was the great-great-grandmother of William's grandmother Queen Elizabeth II. The relationships are easier to follow using the ancestry tree with ahnentafel numbering.

Other German definitions

European nobility took pride in displaying their descent. In the German language, the term "Ahnentafel" may refer to a list of coats of arms and names of one's ancestors, even when it does not follow the numbered tabular representation given above. In this case the German "Tafel" is taken literally to be a physical "display board" instead of an abstract scheme.
In Nazi Germany, the Law for the Restoration of the Professional Civil Service required a person to prove non-Jewish ancestry with an Ariernachweis. The certificate could take the form of entries in the permanent Ahnenpass or as entries in a singular Arierschein that was titled "Ahnentafel".

Software