How many people are in your Genealogy Database?

Submitted by ian on Wed, 02/09/2011 - 10:19

After reading a blog post on Dick Eastman's website (EOGN), I was interested to see where my database sits in comparison.  The table originally posted on Mr. Eastman's Blog is slightly different than the one have posted below.  Mine is setup to include myself (or yourself) in the calculations.  So for generation 1 you have 1 person in the tree, yourself.  Generation 2 has 3 individuals in the tree, which represents your 2 parents and yourself for a total of 3.  With the third generation you get yourself, your 2 parents, your 4 grandparents for a total of 7 individuals.  You get the idea.  These numbers only count those individuals from which you descend, so no siblings etc.  


Generation Number of individuals
1 1
2 3
3 7
4 15
5 31
6 63
7 127
8 255
9 511
10 1,023
11 2,047
12 4,095
13 8,191
14 16,383
15 32,767
20 1,048,575
25 3,355,444
30 1,073,741,823
35 34,359,738,367
45 35,184,372,088,830


To me the numbers are interesting.  According to Google the Earths population in 2009 was 6,775,235,741 or almost 7 trillion people.  Looking at the table above, if you were able to document 35 generations of individuals, you would have almost 5 times that number in your tree.  If those numbers seem unreasonable to you, you are not alone.  Even if you were able to document 35 generations, it is highly unlikely that you would actually ever achieve those numbers, as the chart makes an assumption that each individual is a new and unique individual.  In real life, this is not likely to happen, as we all know fourth, third and sometimes even second cousins can marry and have offspring, so the number in reality is not that large.  This phenomena is known as ancestor collapse or pedigree collapse.  

To me the most striking number was the one at 45 generations, if you had all unique individuals, you would have more than 35 quintillion people.  For me this number is boarding on being to large to comprehend.  To put the number into perspective, lets compare the number to the total individuals that have ever been born on the planet Earth.  Based on an article the total number of people estimated to have ever lived on the earth ever is only 106,456,367,669 or 106 trillion people.  The number listed at 45 generations is approximately 330 times larger.

You may ask who cares, and I am not sure that I have a good answer, but I am looking at the numbers as a tool to gauge how well I have been doing my research.  My current tree has 2,368 individuals (as of 2-9-2011) in the tree.  If you look at the number of individuals in the chart above, those numbers would point to about 11 generations back. I can assure you that I have not been able to trace 11 generations deep on all of my lines.  On my "Main" line of Towler/Toler/Toller I am 14 generations deep, but I know on my maternal side I have lines that only go 5-7 generations deep.  The number of individuals in my tree is skewed a bit, as I include siblings etc., but I still feel like it is an interesting metric to look at to see how you are progressing in your research.

Perhaps my goal for next year will be to trace my all of my lines back to 10 or 11 generations.  It would be a challenging goal, but fun to try to achieve.