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How Many Ancestors Do You Have?

9 Jul 2021 1:42 PM | Anonymous

Do you know how many ancestors you have? Of course not. Let’s simplify the question: How many ancestors do you have in the past one thousand years? Many people do not know the answer to that question. Care to guess? (The answer is given below but please don’t peek just yet.)

The number of ancestors is simple to calculate as it is a simple mathematical progression: every person has two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents and so on. The number doubles with each generation. As you go back in years, the numbers soon become very large.

For this example, I have assumed that a new generation appears on an average of every twenty-five years:

Number of Ancestors

Generation Number # of Years Before Your Birth Number of ancestors in that generation Total ancestors (this generation plus all later generations)
1 -25 2 2
2 -50 4 6
3 -75 8 14
4 -100 16 30
5 -125 32 62
6 -150 64 126
7 -175 128 254
8 -200 256 510
9 -225 512 1,022
10 -250 1,024 2,046
11 -275 2,048 4,094
12 -300 4,096 8,190
13 -325 8,192 16,382
14 -350 16,384 32,766
15 -375 32,768 65,534
16 -400 65,536 131,070
17 -425 131,072 262,142
18 -450 262,144 524,286
19 -475 524,288 1,048,574
20 -500 1,048,576 2,097,150
21 -525 2,097,152 4,194,302
22 -550 4,194,304 8,388,606
23 -575 8,388,608 16,777,214
24 -600 16,777,216 33,554,430
25 -625 33,554,432 67,108,862
26 -650 67,108,864 134,217,726
27 -675 134,217,728 268,435,454
28 -700 268,435,456 536,870,910
29 -725 536,870,912 1,073,741,822
30 -750 1,073,741,824 2,147,483,646
31 -775 2,147,483,648 4,294,967,294
32 -800 4,294,967,296 8,589,934,590
33 -825 8,589,934,592 17,179,869,182
34 -850 17,179,869,184 34,359,738,366
35 -875 34,359,738,368 68,719,476,734
36 -900 68,719,476,736 137,438,953,470
37 -925 137,438,953,472 274,877,906,942
38 -950 274,877,906,944 549,755,813,886
39 -975 549,755,813,888 1,099,511,627,774
40 -1000 1,099,511,627,776 2,199,023,255,550

Answer to the earlier question: If we assume that there is a new generation every twenty-five years, an ancestor born 1,000 years before you would be 40 generations removed from you. You would have 2,199,023,255,550 (that’s 2 trillion, 199 billion, 23 million, 255 thousand, 550) unique ancestors born in the previous 40 generations, assuming no overlap (that is, none of your ancestors were cousins to other ancestors).

1,000 years doesn’t even take you back to the years in which Charlemagne lived! (April 2, 742 AD to January 28, 814 AD)

Now, how many ancestors have you had in the past 10,000 years? 100,000 years? I’ll leave it to you to figure out the mathematics involved. However, the answers obviously are huge numbers!

There is but one problem: all of these numbers are far more than the total number of people who ever lived on the face of the earth.

The reality is that all families can find lots of cousins somewhere in the limbs of the family tree, resulting in the same ancestor(s) showing up in multiple places in the pedigree charts. Ask anyone who has done French-Canadian genealogy or has researched any families that lived for generations in one small village almost anyplace on earth.

Obviously, you and everyone else have cousin marriages in your ancestry, resulting in individual ancestors showing up in multiple places in your family tree.


Comments

  • 11 Jul 2021 9:22 PM | Anonymous
    The average generation is not 25 years. Studies have shown that can vary, depending on the country or region, but 25 years is too low. A better rule of thumb is 33 years per generation. Test it against your own family tree and see the results.
    Link  •  Reply
    • 26 Jul 2021 2:02 PM | Anonymous
      --> Test it against your own family tree and see the results.

      The quick answer is "it varies."

      In my case, 50% of my ancestors are French-Canadians. Throughout history, French-Canadian females married young and had children starting at an early age. Most French-Canadian females had their first child when they were 15 or 16 years of age.

      Other ethnic groups obviously had different statistics.
      Link  •  Reply

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