On Genetic Trivia

When I considered the issue of children as a genetic footnote to leave behind as a mark of someone’s existence, I started to play with the mathematics of ancestors and descendants. Bear with me for a few moments as I lay out my reasoning.

Pedigree XYConsider the fact that we have 2 parents, 4 grandparents, 8 great-grandparents, 16 great great-grandparents and so on, as the generations go further from us. See the chart below for a more detailed delineation: I have considered the first ancestral generation after us to begin with our parents.

You (or me)
1st generation = 2 parents
2nd generation = 4 grandparents
3rd generation = 8 g grandparents
4th generation = 16 gg grandparents
5th generation = 32 ggg grandparents
6th generation = 64 gggg grandparents
7th generation = 128 ggggg grandparents
8th generation = 256 gggggg grandparents
9th generation = 512 ggggggg grandparents
10th generation = 1024 gggggggg grandparents

Adding up all the ancestors including our parents, we have a total of 2,046 direct ancestors. As the generations move further away from us, the genetic relatedness gets more and more diluted, unless there is a specific dominant gene associated with some genetic disease that passes direct from one generation to the other. Another exception is the male gene which is the only one that passes virtually unchanged from father to son. Other than these two exceptions the genetic relatedness to any of the 2,046 direct ancestors of the ten generations becomes so diluted that it’s as genetically similar to us as a complete stranger passing us in the street. Hmmmmmm

Generic Family TreeMy point is that we know only our parents, grandparents and perhaps our great grand parents, our children, grandchildren and perhaps our great grandchildren. Three generations around us. All the rest beyond our great grandparents and great grandchildren are strangers, because they died before we were born, or we died before they were born. From the genetics standpoint, we have almost as much in common with them as total strangers. The genes get so diluted that the actual family ties become more like loosely related clan of ethnic and cultural connective-ness rather than familial bond.

Since the advent of plane travel and migrations of large segments of the population from their traditional homelands, it will increasingly become more likely that someone we pass in the street on any given day may share at least one common ancestor. That would make them distant cousins, but never the less related.

Finally, Dear Abby once had an article defining the difference between first, second and third cousins, as opposed to first cousin once or twice removed. According to her, first cousins share grandparents, second cousins share great grandparents, third cousins share great great grandparents, and so on. First cousin once removed are the children of my first cousin, while my first cousin’s grandchildren become my first cousins twice removed. However my children are related to my first cousins children as 2nd cousins. My grandchildren are related to my first cousins grandchildren as third cousins.

Now that this is all clear, we should all be more careful of the stranger in the street, because they may be a distant relative.

How is that for genetic trivia?