Friday, January 2, 2009

Your Family Tree is Actually a Family Diamond

Many times people trace their family tree back to royalty or famous people and are somewhat proud to find who they are descended from. But the broader truth of the matter is more amazing than most people imagine. Ask yourself this question: How many people (i.e. positions in your family tree) do you think you have in 1100 A.D. (about 900 years ago)?

Your Ancestors
You can calculate the answer. If you assume 30 years to be an average generation, then every 300 years
(10 generations) you have 1024 ancestors (2 parents, 4 grandparents, 8 g-grandparents, and so on up to 10 generations) and every additional 300 years multiplies the effect. So, 600 years ago you had about one million places in your family tree chart and 900 years ago, 1100 AD, you had approximately one billion ancestors in your family tree! And if any one of those ancestors had died before having children, you would not be here today.

Now you may say, wait a minute that is too many ancestors, there must be a miscalculation. In 1000 A.D. there was only an estimated 310 million people alive and it is estimated that there wasn't a billion people in the world until 1804. The difference is that you have people who are related to you in more than one way. It is true that if you draw out your family tree, you will have around one billion slots
to fill 900 years ago, but some individuals will fill many of the different slots.

What can we understand from this? Basically, it appears that when you go back 900 years or more, it is probably more accurate to say you are related to whole people-groups, i.e., most everyone in any group that intermarried. For example, if you have English royalty in your ancestors, it is probably more accurate to say that you are related to most of England at the time. You only have the records of the royalty in your ancestry because royalty were the only ones we have kept records that far back for.

Your Descendants
Now the same math works for the future as well as the past. If your descendants average two descendants every generation of 30 years, in 900 years you will have approximately one billion descendants, but of course you will be only one of their one billion ancestors and you will likely be in their family tree in more than one slot. And the interesting thing is, now that births are fully recorded in most countries, 900 years from now your descendants will probably have all those slots filled in their one billion entry family tree. They may even have pictures and biographies of many of their one billion ancestors.

Think of the shape of your full family tree. We call it a "tree" because that is the only part of the diagram that we know. Our actual family "tree" is in the shape of a diamond with an upside down tree on the bottom of the diamond, i.e., the shape you see at the start of this post (time goes from the top to the bottom, the number of your relatives is the width between the two lines). The first humans (either Adam and Eve, or the first "human" mutations, depending on your beliefs) are at the top where the two lines meet, you are where the bottom lines cross and your descendants are the area between the two end points of the lines at the bottom of the drawing. We think of our ancestors as a tree shape because that is the portion of people we know back "up" the diamond a little way. We don't have records back to the time when the tree shape starts converging back into a diamond shape.

At this point you may be thinking: that is quite interesting but what is the practical application of this knowledge. Here are some ways this can change your ways of looking at the world:

1. When you study early history, if you understand that you are related to whole nations and people groups, that makes the history much more interesting.
2. In trying to influence your descendants, to leave a lasting legacy you must leave them something that will influence your descendants over time more than all their other ancestors,
otherwise you and your memory will be lost in a mass of ancestors in just a few generations.
3. Try to influence society at large rather than just your kids, since in 900 years your descendants will most likely be most of society itself. And if you don't have kids you can have the same affect by working to influence society and other people.

So, you are truly part of the human race. In history and in the future ( if you have kids) you are related not just to individuals, but to people-groups.