Our Common Ancestry

Let me share with you a thought experiment. This involves a little math, but the storyline is compelling, I promise.

Every one of us is blessed with two parents. And every one of us is blessed with four grandparents. Likewise, we are blessed with eight great grandparents and sixteen great great grandparents.

I knew, personally, each of my grandparents before they died, but I never knew my great grandparents. I don't even know their names. I need to find that out.

If you consider that each generation, on average, reaches age 25 years before having children, then we can assume that with every 100 years, four generations of every family come and go.

By that metric, my 16 great great grandparents were in the prime of their lives around the year 1900. Moving further back into the past, I had 32 ancestors around 1875, 64 ancestors around 1850, 128 in 1825 and 256 in 1800. As you can see, with each generation (25 years), my family tree doubles.

Moving still further back in history, to 1700, my direct ancestors numbered 4,096.

In 1600, my ancestors numbered 65,536.

In 1500, my ancestors numbered 1,048,576.

That means that around the time of Columbus, my family tree numbered over 1 million.

But here's where things get interesting.

My father's side of the family is Irish, which means that half a million of my ancestors (presumably) lived on Ireland in 1500. Furthermore, in 1475, my Irish ancestors number 1,048,576.

However, around the year 1500, the population of Ireland was estimated to be 1 million souls. That means, theoretically, that every Irishman alive in 1500 was either a person in my family tree, or is a person whose family tree did not survive to the present day (they or their descendant's had no offspring).

This to me is amazing, because it tells me something very important. Every single person of Irish decent today is a cousin of mine-- I only have to trace my family tree back 20 generations (to the year 1500), to find a common ancestor. That means that people alive today of Irish decent are no more distantly related than 20th cousins.

My wife Crystal is of Scotch-Irish decent. That means that the two of us are, with very reasonable certainty, at least 20th cousins. We may be two or three generations closer than that.

But it gets better.

If we move further back in history, to 1400, my ancestors number 16,777,216.

In 1300, my ancestors number 268,435,456.

Now my mother's family was French, having immigrated from Normandy to the US just before World War I. As such, half of my family tree originated on Continental Europe.

Funny thing is, in the year 1300, the entire population of Europe was estimated to be between 70 to 100 million. This means that in 1350, my family tree included nearly every European alive at that time, give or take a generation or two.

Again, there were no doubt a sizable number of Europeans of that day who did not have any offspring, or whose families eventually died out over the years. My family tree does not touch them, and nor does anyone else's.

However, it is reasonable to assume that if I meet anyone of European decent today, that person and I are no more distantly related than 28th cousins, give or take a generation or two.

I find this sort of analysis to be fascinating. It really speaks to the closeness of the human family. We are all so much more closely related than we realize.

It means that every single person of European decent alive today shares a common ancestry with every European in history beyond the year 1300 (or thereabouts), assuming that person spawned a continuous ancestry that survives today.

It means that if one European alive today can claim to be an ancestor of Charlemagne, he or she has proven that every other European alive today is also an ancestor of Charlemagne.

Likewise, every Arab alive today is, literally, a direct descendant of the Prophet Mohammad. And every Chinese alive today is a direct descendant of Confucius.

Taking my own family tree still further back in time, I must take into account my ancestors who served as bridges across civilizations-- the Christopher Columbuses and the Marco Polos. These people led or were part of expeditions across the globe, and through the resulting inter-marriage and offspring, serve to link all family trees in the world to one another.

In this way, my ancestry does not stop at the borders of Europe. With each generation, and the exponential growth of my ancestry, I can claim common ancestry with Africans, Arabs, Indians, Chinese and Japanese. It is merely a question of how many generations I need to traverse through time to find a common ancestor.

Again, if I double my ancestors every 25 years beyond 1300, I find that my family tree would number 4,294,967,296 in the year 1200. Obviously, this number exceeds the entire population of the world at that time. This fact points out the fact that my ancestors, beyond some point, say in the year 1300, merely intermarried with their distant cousins. My family tree becomes a network at that point, repeatedly interconnecting with itself through the ages.

However, it is these human bridges, like Marco Polo, who were able to branch my family tree far beyond my European trunk. And with each doubling of succeeding generations, these single branches grow into other networks of cousins, until my family network eventually touches every corner of the Earth.

Demographers today estimate that humankind's Most Recent Common Ancestor, the man and woman whose resulting family tree now touches every single human's current ancestry, probably lived in the year 200 BC. That was 88 generations ago.

This takes us to our ultimate conclusion: every single person alive today, no matter where they live, what they look like, or what language they speak, is no more distant from me than 88th cousin. Some people, like those of European decent, are between 20th and 25th cousins to me. Others, like Chinese, Africans, etc, are between 75th and 88th cousins to me.

For instance, Senator John McCain is of Scotch-Irish decent. He is most likely a 20th cousin of mine. Likewise, Senator Barack Obama, who is of Kenyan-French-German-Irish-English decent, is probably between a 25th and 30th cousin to me.

There are six billion people alive today on Earth. None of them are "strangers". All of them are my cousins. The question is only how distant.