When we talk about our ninth great grandparents, how many years ago is that? Our ninth great grandparents are twelve generations ago - counting the three generations to get to our first great grandparents.
People have kids when they are teenagers; some have kids in the 40's; so what would be the nominal or average number to be used when thinking about this period of time?
How many years in a generation.
For the purposes of this post, the related question is, "How many generations in a century?"
We have sound empirical evidence that the answer is 3. Not "about 3" but 3. Check this out then continue below the chart:
I don't think my mother noticed this pattern until her granddaughter Wendy was born.
Wendy was born in 1968, 100 years after her great grandmother Maggie (Rowlison) Cassell in 1868.
I was born in 1943, 100 years after my great grandmother Rhoda (Walton) Rowlison in 1843.
My Mother, Mildred (Cassell) Johnson was born in 1912, 100 years after her great grandfather Isaiah Walton was born in 1812.
So there you have it, three generations in exactly 100 years and it happened three consecutive times in this lineage.
The pattern is broken with Isaiah's father Abraham Walton who was born in 1777 instead of 1768 which would have fit the pattern. But look at his father. William Walton was born in 1743 which did fit that pattern joining Rhoda (1843) and myself (1943)
So for this line, the average number of years in a generation is 33 1/3 over a period where this pattern held. Kind of cool. A coincidence of course but still cool. The real reason this worked is that Mildred was the ninth of Maggie's children, born when Maggie was 44 years old. That needed to happen again if the pattern were to continue. And you'll notice that the pattern has been broken. Wendy did not present us with another grandchild last year. Yes, I did mention this to Wendy early last year. I will not quote exactly what she said; the response I got indicated pretty clearly that this was not likely. It was not just, "No." But more along the lines of, "Hell, no!" As I said, I will not quote her exactly.
The better way to see how many years in a generation is to average the birth years at a given generation in the past. I'll use my own second great grandparents, the generation of Isaiah Walton and Aaron Rowlison (the younger).
My great grandparents were born in:
1794 Johannes Jonasson
1796 Lena Cajsa Petersdotter
1811 Jonas Petter Klintberg
1807 Ingri Cajsa Persdotter
1804 Israel P.Aspegren
1813 Anna Carin Petersdotter
1824 Andrew Peter Israelson
1833 Charlotte Sophia Larsdotter
1795 James Cassell
1791 Janet Laing
1802 William Maxwell
1806 Elizabeth Inglis
1809 Aaron Rowlison
1813 Martha Ann Kinnear
1812 Isaiah Walton
1817 Eliza Jane Hall
(Not too hard to pick out the eight Swedes and the four (actually 5) Scots there.)
The range of birth years for these people is from 1791 to 1833. The average birth year for my great, great grandparents is 1808 or 135 years before my birth in 1943 - an average of 27 years per generation.
For the math kids, five generations back you have 16 great grandparents. What's the math for that? Remember exponents? The number of ancestors at any level is 2 to the Nth power where N = the number of generations. Two to the 5th power is 16. Ten generations back is 2 to the 10th power or 1024. At the 20th generation, you have over a million ancestors and at 30 generations you had a BILLION ancestors, or probably about the population of the planet.
Thirty generations by our math above, will be about 900 years,
only 900 years or the early 12th century. I have our lines back to Charlemagne, to the Plantegenet Kings of England
http://en.wikipedia.org/wiki/House_of_Plantagenet, some French and Spanish royalty, Geoffrey de Bouillon
http://en.wikipedia.org/wiki/Godfrey_of_Bouillon and a bunch of other folks. It may sound like a big deal but at those levels, probably almost everyone is descended from all of them. The distinction is that some of us can trace those lines, others can't but could with some work.
A second reason not to get to excited about famous ancestors of the past is that the basis of genealogical research is to follow the biological path back to your natural ancestors. We know that following the maternal lines, the lines of our mothers, is much more reliable than the paternal lines. We know for certain who a newborn's mother is; she will be close by. Being certain of the father is, when we're talking about 10 or 20 generations (even fewer) a bit more problematic. Genealogist and others call this the "paternity anomaly."
On a more benign level, adoptions were not always well documented. We do see census records where a child is listed as an "adopted son" or "adopted daughter" but I've not seen it very often, far less than I'd expect was the case. It was very common for children to be raised by people not their parents in earlier times when mortality rates were higher among young adults.
But if we understand these shortcomings and keep a clear head about what is actually going on here, it still is interesting, even somewhat comforting to be able to look at a list of 16 specific individuals from the early 19th century and know that your entire genetic makeup comes from those people and to the extent that Nature rather than Nurture determines our innate qualities, these folks "are" us, for Good or for Bad.
.jpg)
