Dr. Platypus

I thought this story about Presidential descendants was interesting:

Former President John Tyler, born 221 years ago, still has two living grandchildren. The one-term president isn’t a well-known historical figure; he’s probably best remembered for helping to push through the annexation of Texas in 1845, shortly before leaving office.

So, how is it possible that a former president who died 150 years ago would still have direct descendents alive today? As it turns out, the Tyler men were known for fathering children late in life. And that math is pretty outstanding when added up:

John Tyler was born in 1790. He became the 10th president of the United States in 1841 after William Henry Harrison died in office. Tyler fathered Lyon Gardiner Tyler in 1853, at age 63.  Then, at the age of 71, Lyon Gardiner Tyler fathered Lyon Gardiner Tyler Jr. in 1924 and four years later at age 75, Harrison Ruffin Tyler. Both men are still alive today.

That means just three generations of the Tyler family are spread out over more than 200 years.

I don’t know how old Lyon Jr. and Harrison were when they became fathers, but the average age for both President Tyler and his son, Lyon, is a whopping 67 years! To put this in perspective, genealogists will usually figure a first child is born when the father is about 20-25. If you’re not worrying specifically about firstborns, the average father-to-son generation length will be a bit longer, but surely not much past 30. But here is a documented account of a father-to-son average generation length of almost 70 years. This is significantly longer than the average 40-year generation length documented in my own family tree over the past six generations.

Of course, I’m thinking about this because of (what else?) the biblical genealogies. We usually don’t bat an eye when we see a genealogy (biblical or otherwise) with generation-lengths in the 20-30 year range. But surely something is amiss if we find some in the 60-70 year range, right? Well, yes, there almost certainly is—but apparently not always. In the great majority of cases, there is most likely a generation or more missing from the record when you find you have to “stretch” the generation lengths to cover the allotted time. Either that or you have over-estimated the time span in the first place.

For example, the genealogies that span from the time Jacob and his family entered Egypt until the time of the Exodus will expand or contract depending on the dates assigned. Even then, however, different genealogical lines cover that period with different numbers of ancestors. Joshua’s (through Joseph) has thirteen. Nahshon’s (through Judah) has seven—or maybe a couple more if you make certain text-critical assumptions about the version of this line given in Luke 3. Moses’s (through Levi) has only five.

Is it really possible that only five generations separate two points in time that other genealogies fill with a dozen or so ancestors? Actually, probably not. I still suspect there are some missing generations in there somewhere. But the genealogy of John Tyler makes the genealogy of Judah look a bit more plausible on the surface. Two or three unusually long generational “jumps” would bring all the rest into something like the expected parameters.