How many ancestors do you have

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. How many ancestors do you have?

Like, a LOT of people. Most of us all of us? There are just too many variables, and besides, not all of our ancestors were born where good records were kept. So, do we really have more than one million 18th great-grandparents? As you can see, doubling the numbers every generation allows the number of ancestors to get really, really big — and really quickly! My ancestry, at a basic level, goes back to Europe British Isles, Western Europe, and Eastern Europe , and 26 generations ago approximately years ago , population estimates for the entire European continent were right about 78 million people.

If I go back one more generation — to 27 generations — and still within the s when about 78 million people lived in Europe , I supposedly have ,, ancestors. More than million ancestors! This is many more ancestors than the number of humans who have ever lived in the history of the world, which is estimated to be at a little over billion people in total. What this means is that some of our ancestors are our ancestors on more than one line of our family tree.

We are now led to the obvious question. We exist, of course, and we also — most definitely — have ancestors. So how many ancestors do we really have? This means that the calculations going back a few generations are accurate — you probably do have 64 distinct great-great-great-great grandparents.

Note : Some of us might find that some of our great-great-great-great grandparents are the same people — more on this — and why — below. Assuming you could accurately trace your family tree back on all lines, you would eventually start to see the same people pop up on multiple lines of your tree. Back in the day, people lived in small communities. It was beneficial to stay where you were born, generally speaking, since you had an established social network that made survival easier.

When people grow up and choose mates, they generally choose people who they know. This happened in my own family tree, and not even ten generations ago. Two of my 64 great-great-great-great grandparents six generations ago were first cousins.

That's why we expect the proportion of Smiths in the phone-book to fluctuate only a little from decade to decade. The surprise comes if we look at inheritance from both parents. Here, the numbers change drastically as the generations go by.

For instance, we have two parents, four grandparents, eight great-grandparents, and so on. Each generation back, we multiply the number by two. This leads to what is called an exponential increase: 2, 4, 8, 16, 32, 64, , , , and so on.

It's not long before we hit huge numbers. Take the specific case of Jesus and King David. The number of generations between them is at least Luke lists 42 generations down the male line, and Matthew gives an incomplete list of These numbers agree reasonably well with an average time between generations of 25 or 30 years - an estimate taken from documented historical records from Iceland and Canada.

That's far more than the total population of the world, of course. This is a good illustration of what's been called the "genealogical paradox". In short, we seem to have too many ancestors. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account.

Notify me of new comments via email. Notify me of new posts via email. Skip to content. How many genomic blocks do you share with a cousin? How many genetic ancestors do I have? Posted on November 11, by cooplab. Share this: Twitter Facebook. Like this: Like Loading This entry was posted in genetic genealogy , personal genomics , popgen teaching. Bookmark the permalink.

Elan says:. November 11, at pm. November 12, at am. Menachem was here says:. April 6, at am. April 8, at pm. Pierre Clouthier says:. April 6, at pm. Bob Jenkins says:. April 20, at am. April 21, at am. Mel says:. January 1, at am. January 1, at pm. FelixGC says:. February 21, at am.