Generational spread

Alicia Crane WilliamsWaiting for the cold spring to turn warm, I was thinking ahead to my mother’s birthday, on May 10, which I always remember as a wonderful spring day with the lilacs in full bloom. That got me to thinking about how old my mother would have been – I thought at first it would be her 110th birthday, but it is only the 109th.

That got me thinking about generational spacing. As a rule, we use 25 years as the average when estimating the number of generations over a span of time, but, of course, human beings are never average.

Mom, Lois, was 40 when I was born. She was 33 when my oldest brother was born and 34 with the second, so her average is around 35 (children delayed first by the Depression and then by the Second World War).

Mom’s Mom, Alice, was 26 when she was born; her Mom, Ida, was 23; her Mom, Eliza, 22; her Mom, Louise, 27; and her Mom, Eliza Marie, 22 (which is as far back as I can go on my umbilical line). For the seven generations in this line between me and Eliza Marie, the average generation is about 23. Clearly, Mom was atypical for that side of the family. Oddly, though, she had more in common with her in-laws.

My Dad, Roger, was only 36 when I was born (Mother met him while he was still in high school and she was the principal’s secretary). His mother, Agnes, was 31 when he was born, the middle of three children. Agnes’ mother, Mary, was 37 when she was born, the oldest of five children of a late marriage (the last born when Mary was 46). Mary’s mother, Hannah, was 38 when she was born, and that is as far back as I can go in that direction. So for the five generations between Hannah and me, the average is about 36½ years.

Mother’s father, Ed, was 26 when she was born; his mother, Clara, was 29; her mother, Clara, again, was 25; and her mother, another Clara, was 31 (there are more generations, but I only have the 5-generation chart in front of me). So for this line between me and the third Clara, the average is about 30 years.

Dad’s father, Will, was 30 when he was born; Will’s mother, Susan, was 33 (but he was the seventh of ten children). Susan’s mother, another Susan, was 38 when she was born, and that is where my knowledge of that line ends. The average between me and Susan #2 is about 35.

Turning the exercise around, here is a chart of ages at death of three generations of my family (using the Ahnentafel numbering system):

2: Roger (97), 3: Lois (99½)

4: Will (85), 5: Agnes (93)

6: Ed (81), 7: Alice (82)

8: William (86), 9: Susan (87)

10: William (56 – died of brown lung disease from working in tapestry mills), 11: Mary (68)

12: Edward (63 – died of blood poisoning), 13: Clara (97)

14: Henry (64 – died of cancer), 15: Ida (81)

Just another way of looking at statistics.

About Alicia Crane Williams

Alicia Crane Williams, FASG, Lead Genealogist of Early Families of New England Study Project, has compiled and edited numerous important genealogical publications including The Mayflower Descendant and the Alden Family “Silver Book” Five Generations project of the Mayflower Society. Most recently, she is the author of the 2017 edition of The Babson Genealogy, 1606-2017, Descendants of Thomas and Isabel Babson who first arrived in Salem, Massachusetts, in 1637. Alicia has served as Historian of the Massachusetts Society of Mayflower Descendants, Assistant Historian General at the General Society of Mayflower Descendants, and as Genealogist of the Alden Kindred of America. She earned a bachelor’s degree from the University of Connecticut and a master’s degree in History from Northeastern University.

25 thoughts on “Generational spread

  1. It is true, human beings will not be typical, however being the eldest of my siblings it is a good starting point for me to use every 20 up. Of course averaging them as I learn their ages when child bearing easily gets into the age 30 or more years, even older back when they did have so many children. Most of mine had, on both sides, families of 10 and 12 children depending on where in the family the ancestor is born is interesting then. This is a very helpful article, often one we don’t stop to think about:) We must be flexible:)

  2. My family is going to confuse future researchers as my younger brother’s oldest grandchild is only 18 months younger than my youngest child. Of course, my brother married at 18, his daughter at 20, and me at 34 (youngest child born when I was 42).

  3. Generational differences are very apparent in my family. My maternal grandparents were born in 1902 & 1904. My mother was born in 1924. My paternal grandparents were born in 1876 & 1880. My father was born in 1919.

    1. This is the situation that drives me up a wall. It seems that most grandparents – and most writers assume that grandparents – were born early 20th century, while mine were born in 1853 and 1867 on one side and 1882 and 1888 on the other. Searching for information in the 20th century is very different from searching mid 19th.

  4. Fascinating, Alicia, both the birth statistics and death statistics. I’ll have to make lists like yours to see what other details I can find in my own family.

    I just lost my mother, at 100 11/12. She was 29 when I, her oldest, was born, late for a WW II baby, and had two more after me. My brother, the middle child, was in his mid-thirties when he had his first child, and that child’s oldest was about the same age. So he was 65 when he first became a grandfather. On the other hand, our father had an early first marriage, and was 22 when his daughter was born, fairly typical in the late 1930s. My half sister had her first child at 20, and her children and grandchildren followed suit. She became a great grandmother at 65. So in my father’s branch of the family, generations are much shorter than in my mother’s branch.

    My paternal grandmother, whom I never knew, was the oldest of 8 children born between 1886 and 1904. The youngest married late, and had her only child at 45, in 1949, also the year my youngest sister was born. This made them first cousins once removed, which was pretty confusing to my sister when they were young and played together at family reunions!

    Thanks for demonstrating that different kinds of charts and statistics can clarify things we only vaguely knew.


    1. Doris, Bless her and you for “raising” her to almost 101! One of my brothers started early, himself, and his oldest daughter started even earlier, and so on, so he became a grandfather at 44, and now at 74 he is a great-grandfather about a half dozen times over — I lose track, myself.

  5. Trying to develop a theoretical model for lineage linking in the late 1970s, we came across a concept called intergenesic interval, meaning the number of months between births for a given mother. It can be a useful tool in estimating the likelihood that two individuals are actually siblings. Some less multi-syllabic term is probably used today. Great for avoiding non-connected mash-ups of families.

    1. I think I’ve read some articles on that subject, too. As I remember, a variable in the equation is whether the mother was breast feeding, which traditionally led to the 2-year average spacing, but if the first child died as an infant, then the spacing would lessen.

  6. Yes, I’m fascinated by this sort of statistical stuff.

    My paternal great grandmother Pearl and my maternal grandmother Gladys were both born in 1892. Pearl had her one and only baby at the age of 16. Gladys had her one baby at 44. I suspect the pregnancies were both unplanned and not welcomed. So when Pearl’s grandson and Gladys’ daughter, essentially the same age, met at college, they married and had me. But it meant there was a whole generation skipped on my mother’s side.

  7. Look at it another way: I was born in 1940, my mother in 1913. Her father, Hiram, in 1853 (she was the youngest of 9), his father, Orlando, in 1824, and his father, Peter, probably in 1797; there’s some indication that his father, James? was born in 1760. What this means to me is that it gets difficult quickly to find good information and verify the details.

  8. I just did a little calculating with my matrilineal line. My 6th great grandmother was born in 1692. The average distance between our generations is 32 years. Of course, we are almost all the youngest daughter.

  9. My mother died when I was 21, she was 63, dad when I was 28 and he was 69, so both would be 111 this year. I miss them more each year and it seems impossible they’ve been gone for so many years.

    1. Martha, I’m sorry that you lost them so early in your life. I remember being afraid of losing my parents when I was a child, too bad they couldn’t have told me how long they were going to live so I could stop worrying! Blessings on them all.

  10. Terrific piece on another way of looking at one’s family. My grandmother was born in 1870 but didnot marry until 1909. My mother born in 1914, I in 1940, but Grandma lived to 101, so I was able to know her well. How I wish I had asked more questions.

  11. Love your blogs Alicia, you always give us something to think about. I guess it’s the ways families tend to make an exception to the standard that likens genealogy to solving a puzzle and so much fun. My mother’s father was born in 1869, she was born in 1903 and I’m a leading edge baby boomer; the 25 year norm would cause one to assume four generations when in fact there are only three. When my mom died in 1999 I remember thinking of the enormous amount of history that had transpired from 1869 to 1999; two generations of one family.

  12. Fascinating! Like Dave’s family, my paternal side has long generations, later children and marriages. I too was born in 1940, my dad in 1910 (an only child after 11 years of marriage which is interesting), his father in 1868 & his mother in 1869, the paternal father in 1819 and his father in 1786 in Prince William CO, VA. It throws all our relationships off by a generation, e.g my dad’s closest childhood cousin was b. 1915, but he is my generation, which makes charting sometimes confusing.

  13. Great article Alicia! I am working on sourcing, but in a weak moment, Having “found” another line back to WMI I decided to see how many “greats” he was to me. One line came out as 29 and the other 30. 32 and 33 generations respectively as I see it. I will really have to study it more carefully using birth dates!! Right now my dad will be 99 next month and his first great g-son will be 3 only three days later. The fun and games go on !!!

  14. Very interesting article. I’ve noticed the same in my family tree. My paternal grandfather was born in 1887, his father was born in 1823, and his father was born in 1773. My maternal grandfather was born in 1901, his father was born in 1856, and his father was born in 1834. My paternal grandfather was 60 years old when I was born in 1947, the first child of my dad’s second wife. My half sister is 12 years older than me. My maternal line had 4 generations in the same space of time that my paternal line had only 3 generations! It also helped that my paternal grandfather was the 11th and last child born to his mom, who was born in 1845.

  15. I was born in 1945. Before that, on my paternal line, the average age between generations was 34 years. My 2nd great grandfather was born in 1795. On the maternal line, my great grandmother was born 11 months before her father died in the Civil War. She lived until 1960, age 96. As a child I was awed by the fact I could touch someone alive during that war.
    I tightened up the numbers by having my first child at age 20.

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