What are the odds that you and I are related?

I recently traced a particular branch of my father's family tree back for 21 generations! Maybe. I'll talk about the maybe part later, but at the moment I can make a pedigree chart starting with my father, then his father - a grandfather I never met, then his father's mother - my great grandmother, then her father, and her father's father, and his father's father, and keep doing this until the chart has "branched" 21 times.

Laura Jane "Jennie" Coleman - my great grandmother - is the key to this prodigious branch. Described as "very skilled and industrious" woman, my parents took a picture - back in 1985 - of a bed spread that she made. And when I say made, she spun the wool into even thread that she had dyed, using walnuts for the browns and berries for the the red color. At that time the spread was nearly 100 years old and still beautiful. My mother said, "the colors are not faded, nor does the wool look old."

The earliest individual in this long line is Sir Roger Coleman (or Sir Roger de Colville), born in 1215 probably in Lincolnshire, England, who married Margaret de Brewes, also known as Margaret Devereaux (de Brewes) or "Margery (de Braose) Colville." They had a son also named Roger and he and his wife had a son Geoffrey, and Abraham was the father of Isaac, Isaac the father of Jacob, Jacob the father of Judah and his brothers... and you know the rest.

Twenty-one generations (or 23 generations from my own grandchildren) poses an interesting question. Just how many people could be descended from Sir Roger? A lot. It's a question that interests genealogists, mathematicians and the curiously idle (like myself), and surprisingly there is a lot of math that one can employ to find the answer, starting with the formula:

Total direct ancestors = (2 to the nth power)- 2, 

where n=the number of generations (counting yourself). 

I was never fond of math, so let me just sum it up. My grandchildren and I are part of more than 16 million directly related ancestors and family members of Sir Roger Coleman and Margaret de Brewes. People who study this stuff say that at 25-30 generations (67,108,862 direct ancestors) any person alive should by pure mathematics have a common ancestor with any other known person, alive or dead.

There's a whole lot more math involved besides the simple formula above. For example, purists insist that one must consider ancestors that pop up in more than one line of descent (like when cousins marry, which happened a lot in the earlier days). This reduces the number of direct ancestors significantly if it occurs in the first 8 or 10 generations. The second problem is that a huge total of direct ancestors does not necessarily mesh with actual population statistics throughout the time span involved.

And the "Maybe" I mentioned at the beginning? It's awfully hard to actually prove kinship through 21 generations. The genealogy program that I use to keep up with kith and kin is linked to a couple of major ancestral databases, including the vast genealogical holdings of the Mormon (LDS) Church. That's where this long list of Colemans came from, but it's only a list, and the LDS database, for reasons of their own, is woefully deficient in actual proof. So, while this line of Colemans is interesting, it may not be accurate.

But what one can take away from this exercise is that the next time some idiot cuts you off in traffic or otherwise riles you, be kind. He or she is probably your 26th cousin, 3-times removed. Heck, it might even be me.