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.