How long is a generation? A quick search will provide a range of answers. This Wikipedia page suggests 20 to 30 years, with the following definition:

A generation refers to all of the people born and living at about the same time, regarded collectively. It can also be described as, “the average period, generally considered to be about 20–⁠30 years, during which children are born and grow up, become adults, and begin to have children.”

Some years ago, at a college reunion, I met a near-contemporary of mine who had just begun a new relationship in his 50s. He already had children from his previous marriage and was hoping to have more with his new, younger partner. From what I remember about the conversation, which took place at about 2am, his new partner wasn’t too keen on the idea but he was hoping that she would change her mind. The children from his previous marriage were born while he was in his 20s and 30s.

He talked me through his family history. Going back through earlier generations, he could trace many ancestors who had fathered children in their 50s. Within a few steps he was back to the early 19th century. His own father had bucked the trend somewhat. He was born in the 1920s and was under 45 when the last of his children was born. (He died aged 98, in 2022.)

My father was born in 1930, and his father was born in 1885. My grandfather was about 80 when the youngest of his grandchildren was born. The oldest of them was born in 1948, so he would have been in his 60s by then.

I have been reflecting on all of this because of something that came up in a music session last night. The organizer of the evening, at a pub in Brentford, asked if we had heard about the person in America who was the grandson of someone who was US President in 1790. We hadn’t, and we questioned the Maths.

After a little digging around this morning it looks like he was thinking of a US President who was born in 1790, rather than in office back then. And it appears that one of his grandchildren is still alive, at the start of 2024. The President in question was John Tyler, the 10th to hold the post. This piece from the Washington Post, from 2020, gives the following summary, all of which was new information to me:

John Tyler, an enslaver who was thrown out of his own political party, the Whigs, for vetoing so many bills, never makes it onto lists of best presidents. But he certainly made his share of history in the White House, where he served from 1841 to 1845. He was the first vice president to assume the presidency upon the death of a president; the first president to have a veto overridden; the first president to endure a House impeachment vote (it failed); the first president to be widowed and to marry while in office; and the president who fathered the most children — 15!

(You can see that the Washington Post and I have different house styles: I capitalize the first letter of President, they do not, and I have left the quote above unchanged.)

John Tyler was still fathering children in his 60s, including Lyon Gardiner Tyler, born in 1853. Like his father, he was widowed and then remarried. He was 75 when his son Harrison Ruffin Tyler was born, in 1928. The Washington Post piece quoted above is about this last surviving grandson of John Tyler. He is also related to William Henry Harrison, the President that Tyler replaced, hence his first name.

According to this Wikipedia page, Harrison Ruffin Tyler is still alive, aged 95, and his three children were all born before he turned 34. If he had followed his father’s lead, and fathered a child at the age of 75, that child would have been born in the 2000s. That would have given us four generations all born in different centuries: great-grandfather in 1790, grandfather in 1853, father in 1928, an average of over 70 years per generation.

How long is a generation? Well, it all depends.