The Gilliland Mystery

Family legend holds that young John was hidden in a well when Indians attacked.  His parents died in the skirmish, and John was raised by an adoptive family.  Whether the Hamilton surname was that of his biological parents or his adoptive ones is unknown.  We don’t even know if the story is true.

John Hamilton was born sometime between 1860 and 1865, according to various sources.  He reported that he was born in Texas, but there are no contemporary documents to corroborate that.  The first confirmed record of John Hamilton is that of his marriage to Mary Rowan Smith in 1888 in Conway County, Arkansas.  He and Mary farmed and raised their family in nearby Yell County, Arkansas.  He died there in 1937.

John’s great grandson Gary has been trying to identify John’s biological parents for several years.

 

DNA Testing Strategy

Autosomal DNA (atDNA) represents all branches of your tree, but it gets “diluted” with each generation.  As a great grandchild, Gary inherited only about 12.5% of John Hamilton’s autosomal DNA.  His best strategy to identify John’s parents, therefore, is to test multiple descendants of John.  There are two reasons to do this.  First, known cousins can be used to eliminate shared matches on Gary’s maternal and grandmaternal lines so that we can focus on those who are related through John.

Second, those other descendants might represent portions of John’s genome that Gary didn’t inherit.  The best way to visualize this is using the Coverage Estimator at DNA Painter.

The nine DNA testers shown in black in the diagram represent roughly 52% of John’s DNA.  That is, these nine kits could conceivably identify about half of the people John would have matched had he tested himself.  In practice, we only have direct access to five of these kits.  All nine can be used to sort matches, but our access only represents about 41% of John’s genome.

Unlike autosomal DNA, the Y chromosome is passed undiluted from father to son.  Occasional changes (mutations) can be used to gauge how many generations separate men whose Y-DNA matches.  Gary and two of his first cousins, SLH and JLH, have done the Y-111 test at FamilyTreeDNA, and two of the three have done the Big Y-700 test.  They are all direct male-line descendants of John Hamilton and match one another as expected with both atDNA and Y-DNA.  However, they don’t match any other Hamiltons; the majority of their top Y-DNA matches have some variant of the surname Gilliland (e.g., Gililland, Gilleland, Gillan, and Gilland).

Other than one another, their top Gilliland matches at the 111-marker level are PG, MG (both exact matches), DG (3 differences), LG (4 differences) and CG (6 differences).  Only PG shares atDNA with any of the Hamilton descendants.

 

Hypotheses

DNA and/or census evidence suggested six hypotheses.  Not all are mutually exclusive.

• Hypothesis 1:  Our John Hamilton is the 17-year-old John Hamilton censused in Cooke County, Texas, in 1880.  He was single, a lodger, and working as a porter in a saloon.  This is the only John Hamilton in that census who was born in Texas, of the right age to be our John Hamilton, and not living with family.  No DNA evidence has been found to either support or refute this hypothesis.
• Hypothesis 2:  Our John Hamilton was the same person as John Gilliland (born circa 1861), son of John R. Gilliland (c.1831–c.1865) and his second wife Charity Wilke, from Van Zandt County, Texas.  The elder John Gilliland died in 1864 or 1865, which partially aligns with the orphan story.  The son was censused with his mother in 1870 but not in 1880.  Could he be the John Hamilton of Hypothesis 1?  If this hypothesis were true, Gary would be a junior third cousin once removed to DG, who matches on 108 of 111 Y-DNA markers.  FamilyTreeDNA gives this match only a 44–60% chance of being within the last 4–5 generations, and DG does not share atDNA with the known Hamilton descendants, so this hypothesis seems unlikely a priori.

• Hypothesis 3:  Our John Hamilton was a son of Joseph Gilliland (1816–1873) of Tennessee.  This hypothesis is supported by an exact Y-DNA match at 111 markers to MG.  If this hypothesis is true, MG would be a junior third cousin once removed to Gary.  FamilyTreeDNA estimates a 98% chance that the connection is within five generations.  However, MG does not share atDNA with the Hamilton descendants, and all of Joseph Gilliland’s known sons can be traced.  None was old enough to have been our John Hamilton’s father.
• Hypothesis 4:  Our John Hamilton was the grandson of Thomas Gilliland (≈1782–1852) and his wife Mary Ann Galliher (b ≈1790) from South Carolina.  This hypothesis is supported by an exact Y-DNA match at 111 markers to PG.  If this hypothesis is true, Gary and PG are 4th cousins.  PG shares atDNA with Gary’s sister (36 cM in one segment) and his two first cousins (23 and 37 cM, respectively; one segment each) but not with Gary or his Hamilton second cousins. FamilyTreeDNA estimates a 98% chance that the connection is within five generations, and we expect about half of 4th cousins to not share atDNA, so the DNA evidence supports this hypothesis. However, none of Thomas Gilliland’s sons are known to have lived in Texas, where John said he was born, or Arkansas, where John lived later in life.
• Hypothesis 5:  Our John Hamilton was the 14-year-old John Hamilton censused in the township of Texas in Craighead County, Arkansas, in 1880.  He is listed as the son of Charles Hamilton and his wife Jane.  They would have been only 17 and 16, respectively, when John was born, and their next oldest child was 8 years younger than him.  The same couple were censused as presumed newlyweds in 1870 with no children, although John would have been at least 5 years old at the time.  Is this our John with his adoptive parents in 1880?  When he said he was born in Texas, was he referring to the township and not the state?
• Hypothesis 6:  Our John Hamilton was someone else entirely.

Big-Y Time Tree

FamilyTreeDNA recently introduced their new Discover™ tools for the Big Y test.  My favorite is the Time Tree, a graphical representation of the time to most recent common ancestor (TMRCA) between the men in the tree.  And it’s really, really cool!

The Time Tree is based on what’s called a “molecular clock.”  In essence, it estimates how frequently SNP and STR changes have occurred per generation throughout history, then calculates how long it’s been since pairs of men in the tree shared an ancestor.  Because DNA mutation is random, there’s necessarily a lot of uncertainty in these estimates.  Fortunately, we can quantify that uncertainty and work with it.  (As an aside, I coauthored a book chapter using molecular clock methods for bees, ants, and wasps.)

This is part of Gary’s Time Tree:

The first branch point, at the upper left, is labeled with the SNP mutation (R-FGC64966) that all seven of the descendants share.  That node occurred sometime between about 600 and 1300 CE (the dashed horizontal line) with an average around the year 1000 CE.  Obviously, that’s too far back to be relevant to Gary’s project, so we can ignore it.

The other nodes are far more interesting.  The one in red (R-BY94024) represents Gary and his cousin SLH’s shared grandfather, who was born in 1897.  The Time Tree average for their grandfather’s birth is 1876, not far off from the truth.

If you go to the “scientific details,” you’ll see a probability curve for this estimate.  Time is on the X-axis and likelihood on the Y-axis.  The higher the curve, the more likely that date is for Grandpa Hamilton’s birth.  The black vertical bar marks the average at 1876.  What’s even more impressive is that the highest point of the curve, called the mode and marked with the red arrow, is around 1895.  This is remarkably accurate!

To address Gary’s question, we’re most interested in the node labeled R-FGC64969.  That’s when Gary shared an ancestor with PG and MG.  Time Tree gives an average birth year of 1643 for that man, with a 95% chance that he was born between 1462 and 1775.  The mode is right around 1650 CE.

That estimate is both disappointing and useful.  It’s disappointing because 1650 is far too long ago to help us identify John Hamilton’s father.  It’s useful because it rules out Hypotheses 3 and 4 (which were based on Y-DNA matches to MG and PG).

By logical extension, we can also rule out Hypothesis 2, which is based on the match to DG, even though DG hasn’t done the Big Y test and is not in the Time Tree.  I say that because MG and PG are exact STR matches to Gary at 111 markers and DG is not (they match on 108 of 111 markers).  If Gary’s shared ancestor with MG and PG was born in the 1600s, his shared ancestor with DG is almost certainly further back.

If the Time Tree is accurate (and I suspect it’s not far off), we’ve been chasing a red herring with those atDNA segments shared by PG and the Hamiltons.  Those segments may have been inherited through the Hamilton’s grandmother or great grandmother; they’re not likely through the Gilliland patriline.

Finally, we have to consider the possibility that John’s father’s surname was neither Hamilton nor Gilliland.  Assuming an average generation time of 35 years, there were six generations between John’s birth and that of the 1650 ancestor.  The surname could have disassociated with the Y chromosome in any one of them.  That is not a happy thought.

 

A Reevaluation

While this result is not what we’d hoped for, it helps us redirect our efforts.  For now, I’m looking closely at Hypothesis 5, that our John Hamilton was the boy censused in Texas Township, Arkansas.  This makes a lot more sense from a geographic perspective than him being the porter in Cooke County, Texas.

Consider this map.  The red points represent the two John Hamilton’s in the 1880 census.  The blue points are the known locations of events in our John Hamilton’s life.  The 1800s in the US were characterized by a steady migration westward.  If the young John in Cooke County, Texas, wanted to farm, he would gone west for cheaper land, not east.  The John in Texas Township, Arkansas, on the other hand, is likely to have moved westward in search of his own property.

Coda

We still don’t know who John Hamilton’s parents were.  One complication is that we’ve yet to find a cluster of atDNA matches that could represent them.  All of the atDNA matches examined so far group with known lineages of the Hamilton tree.  That in itself may be informative; it may be telling us that John Hamilton was related to his wife’s family somehow.  That would not be unusual in farming communities of that time.

Gary is excited to see if any new clues about John’s ancestry show up in the comments about this story.  Do you have Gilliland ancestors?  Please chime in!