Click on an image to enlarge it.
I loaded Ancestry’s ThruLines page recently to see if a particular cousin showed up in it so that I could possibly figure out who her parents and grandparents are since their names are private in her tree. Her great-grandfather isn’t private, however, and I know where he fits in my tree (he’s the grandson of my 2nd-great-grandparents Wallace Dennis and Mariah Herod). She’s my third cousin 1x removed.
When I loaded ThruLines I was surprised to see that it had been updated (I wish Ancestry would let you know when it is) and was extremely surprised to see it had suggestions for 4th and 5th great-grandparents. As an African-American I figured it would take years to discover a 4th-great-grandparent since all of my 3rd-great-grandparents became adults before Emancipation and enslaved people were rarely documented by name in government records. Either years or never.

Suggestions aren’t guaranteed to be accurate. I have parent suggestions for a brickwall great-grandmother that I’m skeptical about because there isn’t any evidence given in any of the relevant trees to back it up. You’d think her parents wouldn’t be so hard to find since she was born in the 20th century, but I digress.
I suspect that at least one of my 5th-great-grandparents was completely Caucasian. I’m about 8% white according to Ancestry. According to 23&Me (because Ancestry doesn’t tell you this), my closest 100% white ancestor was likely born between 1740 and 1830 (I’m about 9.8% white according to 23&Me, by the way). Most of my ancestry is African as expected.

I decided to start my exploration with Tyler Logan (1803 – 1884) who Ancestry is suggesting is the father of my paternal 2nd-great-grandfather Henry Logan (1837 – ~1920). Tyler is the son of Andrew T. Logan displayed in the ThruLines screenshot above. The information about Tyler and Andrew comes from the tree of a woman living in Australia (here is some of the same information on FamilySearch). I doubt that Tyler Logan is my 3rd-great-grandfather, however. He was white and Henry was never recorded as mulatto in any US census record (ThruLines obviously doesn’t take ethnicity into account). I do, however, think that Tyler Logan was Henry Logan’s former slave owner. Tyler moved from Abbeville County, South Carolina to Abbeville, Mississippi between 1830 and 1840. He brought enslaved people with him because he is recorded as having them in the 1830 US Census (line 8, the names of the heads of household are on the previous page). Most of Henry Logan’s US Census records state that his parents were born in South Carolina (he was born in Mississippi).
The 1850 Slave Schedule for Tyler Logan lists a 13-year-old black boy (unnamed because the enslaved were never named in these documents), which means he had been born in 1837—Henry Logan’s birth year. There is a 45-year-old black female also listed under Tyler Logan; maybe Henry’s mother? I will write a separate post about my attempts to figure this out.
So, I didn’t find even some of the names of Henry Logan’s ancestors, but I think ThruLines helped me add a different piece to his puzzle. I can cross Andrew T. Logan and Nancy Ann Meriwether (Andrew’s wife) off my list of potential 4th-great-grandparents and cross Nancy’s parents Zachary Meriwether and Jane Lewis off my list of potential 5th-great-grandparents. I will continue to investigate the others in the screenshot.

If interested, I created WikiTree spaces for Andrew Logan and Tyler Logan to document their slaves.