1) Here is my 23andMe Ancestry Timeline:
The line below "Your Ancestry Timeline" header says:
"How many generations ago was your most recent ancestor for each population?"
The link below the chart says "Learn more about how to interpret this result." I clicked on it and saw:
"This module uses your Ancestry Composition results to estimate the generation range where you are likely to have had a single relative who descended from a single population.
"These results may be helpful for learning about your genealogy, in figuring out from which ancestors a particular ancestry may have been inherited, or for piecing together the history of their likely migrations.
* For technical details on how this feature works, read our white paper."
There is a scale of years across the top of the chart from 1910 back to 1670, with 30 year increments.
2) There are five colored bars that extend over a portion of the timeline. My five color bars are (with the years listed, and the ethnicity percentage) for:
* British and Irish (blue): 1850 to 1910 (47.9% ethnicity)
* French and German (light blue): 1820 to 1880 (26.0% ethnicity)
* Scandinavian (indigo): 1730 to 1820 (2.0% ethnicity)
* North African (purple): 1670 to 1760 (0.1% ethnicity)
* Native american (yellow): 1670 to 1760 (0.5 % ethnicity)
When you roll your mouse over each color bar, you see a message like this (for the Scandinavian bar):
"You most likely had a second great-grandparent, third great-grandparent, fourth great-grandparent, or fifth great-grandparent who was 100% Scandinavian. This person was likely born between 1730 and 1820."
3) So how accurate are these Ancestry Timeline estimates? I considered my known family tree, and the timeline ranges, and determined:
* British & Irish: My great-grandfather, Thomas Richmond (1848-1917) was born in Wiltshire in England, and both of his parents, and probably every ancestor back to Norman times, were born there also. This estimate is judged Accurate.
* French and German: My 3rd great-grandfather, Henry Carringer (1800-1879) was born in Pennsylvania, but his parents (Martin Carringer and Mary Hoax) were children of German immigrants. This estimate is judged Accurate.
* Scandinavian: I don't have any known Scandinavian ancestors back to the early 1600s, and perhaps earlier. I do have some French and Dutch ancestors who came to America in the 1620-1700 time frame that might have had Scandinavian genes. There may be some of my English ancestors form the 1620 to 1700 time frame that were from Scandinavian stock. This estimate is judged as Possible.
* North African: I have no known North African ancestors. Perhaps some of my French and English ancestry from the 1500 to 1650 time frame includes a North African ancestor, but I doubt it. However, I don't know who some of my 4th and 5th great-grandparents are, and it may be that one of them had a North African ancestor. The 0.1% ethnicity implies an 8th great-grandparent of mine. This estimate is judged as Possible.
* Native American: I have no known Native American ancestors. However, I do have a French-Canadian ancestor (3rd great-grandmother Sarah Fletcher) born in about 1800, and her grandparents, great-grandparents might have been Native American. That fits the 1670 to 1760 time frame. The 0.5% ethnicity implies a 6th great-grandparent of mine. This estimate is judged as Possible.
So there we are. I think that this Ancestry Timeline is interesting, and is fairly accurate within the known limitations of my known ancestry and the vagaries of the Reference Groups used for the autosomal DNA analysis.
Copyright (c) 2017, Randall J. Seaver