Your ancestors increase exponentially each time you move back one generation. You have 2 ancestors, if you only go back one generation (your parents). You have 6 total direct bloodline ancestors if you go back two generations because you count your patents and both sets of grandparents. If you go back three generations you have 14 ancestors, which include your 8 great-grandparents, four grandparents and 2 parents.
Following this logic you can determine the number of ancestors at any given generation using this formula:
Total direct ancestors = (2 to the nth power)- 2, where n=the number of generations back
Using this formula when we get to 30 generations we have more than 2 billion ancestors, at 40 generations we have more than 2 trillion ancestors and at 50 generations we calculate more than 2 quadrillions of ancestors.
Problems with these calculations
Although this is mathematically correct, it is not genealogically correct, as we know that the world population did not reach to 1 billion until the 1800s.
We have an explanation for this difference. If you have traced your ancestors for a few generations it is almost certain you have found a marriage between relatives (even first of second cousins). In rural Spain marriages usually happened in the same village or the vicinity, therefore marriages between relatives were very common. These inter-family marriages decrease dramatically the number of real ancestors and the more often it happens, the greater still the reduction. A couple of marriages between cousins happening in the XIX century and your number of ancestors will be reduced by billions at the 30th generation.
This makes the number of ancestors much more realistic, as the mathematicians using statistical sampling techniques have estimated that we only have 25,000 unique ancestors at 30 generations, and no more than 100,000 unique ancestors through 100 generations (100 generations would put us 1,000 years before Christ)
· The odds are in favor that you reading this note and myself are family; the challenge will be tracing our lineages to find that common ancestor.
· Going back 30 generations (about 1,000 years) all of us with European ancestry will have at least one Asian ancestor.
· It is quite likely that two people that have full Spanish ancestry (2 parents and 4 grandparents) do not have to go that far in time to find a common ancestors. They will find it in about 15 or 20 generations (1400 to 1500). If they belong to the same geographical region it will be less than that.
· Guy Murchie has estimated that all living human beings are related at least in family relationship of 50th cousin. That means that any living person’s family tree regardless of its race or geographical origin will share at least one ancestor before the 50th generation (that is around the year 500).
· A Chinese and an African that has never visited China will be relatives. The nomadic tribes would be the link between these distant locations. This is the beauty of genealogy; we are all family, a human race sharing a common origin.
On a lighter note, next time you get frustrated with a telemarketer calling you at dinner time, be nice and think it is probably your 20th cousin calling you ;-)