Decoding Ahnentafels Using Binary Numbers

In the last post, about reading ahnentafels, I showed how to determine relationships by repeatedly dividing by two. Since 2 is the basis of the binary numbering system, we can use binary numbers to simplify the relationship calculation. It offers more flexibility than just repeated dividing.

Here is the same partial ahnentafel that was used in the previous post.

1. Barack Hussein Obama, Jr. (1961)
2. Barack Obama (1936-1982)
3. Stanley Ann Dunham (1942-1995)
4. Onyango Obama (1895)
5. Akumu
6. Stanley Dunham (1918-1992)
7. Madelyn Lee Payne (1922)
8. Obama, of Kendu Bay, Kenya
9. Nyaoke
12. Ralph Waldo Emerson Dunham (1894-1970)
13. Ruth Lucille Armour (1900-1926)
14. Rolla Charles Payne (1892-1968)
15. Leona McCurry (1897-aft1930)
16. Obiyo
24. Jacob William Dunham (1863-1936)
25. Mary Ann Kearney (1869-1936)
26. Harry Ellington Armour (1874-aft1930)
27. Gabriella Clark (1877-aft1930)
28. Charles T. Payne (1861-aft1920)
29. Della Wolfley (1863-aft1900)
30. Thomas Creekmore McCurry (1850-1939)
31. Margaret Belle Wright (1869-1935)
32. Okoth
48. Jacob Mackey Dunham (1824-1907)
49. Louisa Eliza Stroup (1837-1901)
50. Falmouth Kearney (1830-1878)
51. Charlotte Holloway (1833-1877)
52. George W. Armour (1849-aft1890)
53. Nancy Ann Childress (1848-1924)
54. Christopher Columbus Clark (1846-1937)
55. Susan C. Overall (1849-bef1920)
56. Benjamin F. Payne (1838-1878)
57. Eliza C. Black (1837-1921)
58. Robert Wolfley (1834-1895)
59. Rachel Abbott (1835-aft1900)61. Elizabeth Creekmore (1827-1918))
62. Joseph Samuel Wright (1819-1894)
63. Frances A. Allred (1834-aft1880)
64. Obongo
96. Jacob Dunham (1795-1865)
97. Catherine Goodnight (1794-aft1870)
98. John Stroup (c1814-1851)
99. Eliza Jane Clemmons (c1816-1882)
100. Joseph Kearney (c1794-1881)
101. Phoebe Donovan
102. Josiah Holloway (1804-1887)
103. Martha Mallow (1810-1888)
104. William Armour (c1812-aft1880)
105. Sarah Poland (1824-aft1880)
106. John Milton Childress (1816-1866)
107. Nancy Conyers (1823-1860)
108. Thomas Clark (1812-1892)
109. Elizabeth Davis (1822-1900)
110. George Washington Overall (1820-1871)
111. Louisiana Duvall (1826-1855)
112. Francis Thomas Payne (1794-1867)
113. Harriet Bowles (1806-1857)

Here is how to use binary numbers to calculate the same relationship between Barack Obama and Thomas Clark that I used to illustrate the divide my 2 method.

Take Thomas’s ahnentafel number of 108 and convert it to the binary number 1101100.

Start with the leftmost digit and write the subjects name after it. Continue by writing mother for each 1 and father for each 0. The result will be:

1 Barack Obama
1 mother
0 father
1 mother
1 mother
0 father
0 father

So, just like in the last post, we can write a relationship statement that Thomas Clark is Barack Obama’s mother’s father’s mother’s mother’s father’s father. Both methods give the same result.

It is also easy to get the number of generations between the President and Thomas Clark. Just count the binary digits and subtract 1 for the subject. There are 7 digits – 1 = 6 generations between Barack Obama and Thomas Clark.

If you want to determine the relationship in more common terms, just write the generation name after each digit in the column.

1 subject
1 mother (1 generat1on)
0 grandfather (2 generations)
1 great-grandmother (3 generations)
1 2cd great-grandmother (4 generations)
0 3rd great-grandfather (5 generations)
0 4th great-grandfather (6 generations)

Thomas Clark is Barack Obama’s 4th great-grandfather and we confirmed that there are 6 generations between them.

Give binary numbers a try when working with ahnentafels. They make relationships easier to figure out.

Note: There are plenty of binary converters available online but an easy to remember and access one is Google Search. Just go to then type the number you want to convert followed by “to binary.” For the example above the we would put “108 to binary” in the search field. The first result will be the conversion.


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