Thursday, August 20, 2009

37-Marker Matches and What They Mean


What happens when you test 37 markers? Does a match of 36 out of 37 markers, commonly abbreviated as 36/37, mean more than 23/24?

Here is some more information from Ralph Taylor on what matches mean when we have 37 loci or markers to consider.

37-marker matches get even more precise. For example, if you share 35, 36 or 37 markers with another Taylor (or someone with your surname, if you are not looking at Taylor project results!) then you share a common ancestor, probably within a genealogic time frame.

o A perfect 37/37: The chances are 90% that your TMRCA is <= 19 generations, >= 1530 AD; 70% prob. is <= 10 gen, >= 1760 AD; 50% is <= 6 gen., >= 1860 AD.

o 36/37: 90% is <= 32 gen., >= 1210 AD; 70% is <= 20 gen., >= 1500 AD; 50% is <= 14 gen., >= 1660 AD.

o 35/37: 90% is <= 45 gen., >= 885 AD; 70% is <= 30 gen., >= 1260 AD; 50% is <= 22 gen., >= 1460 AD.

However when you have 37 markers to compare, and you don't match 35 or more, such as 33-34/37: You share a common ancestor, but probably not within a genealogic time frame.

§ 34/37: 90% is <= 57 gen., >= 580 AD; 70% is <= 40 gen., >= 1000 AD; 50% is <= 31 gen., >= 1235 AD.

§ 33/37: 90% is <= 69 gen., >= 285 AD; 70% is <= 50 gen., >= 760 AD; 50% is <= 40 gen., >= 1010 AD.

When we get to 32 matches out of 37, or worse: You may share a common ancestor, but the probability that he lived in within a genealogic time frame is small. The 50% probability level for a 32/37 match is <= 51 generations, >= 735 AD.

For some of you, these discussions of probability and statistics are dull. However, they are necessary to understand the meaning of genetic genealogy. We will have future posts with specific examples. For now, consider that your surname is Taylor. You have a family tree with some degree of confidence. Your fourth cousin, another male Taylor descended from the same line also tests. Now, if you match 37/37 or 36/37, this suggests that the family tree is correct for both of you. If, however, your match is 32/37 or less, the family tree is not correct for one or both of you. Because two males from the same male line, only separated by 6 generations would not differ to this extent.

May all your genealogical puzzles be solved!


Friday, August 14, 2009

25-Marker Matches

What happens if/when we have 25-marker matches?

Well, the good news is that 25-marker matches allow finer interpretations:

· 24-25/25: You share a common ancestor, probably within a genealogic time frame. (The numbers of generations & dates below are approximate.)

¨ A perfect 25/25: The chances are 90% that your most recent common ancestor is within the past 28 generations, roughly since 1300 AD. It’s 70% that the time to the most recent common ancestor (TMRCA) is within 15 generations >= 1630 AD and 50% the TMRCA is <= 9 gen., >= 1780 AD. Thus, as we will find out when we look at greater numbers of markers, discovering a "perfect" 25/25 match only means that you share an ancestor who lived about 1300 (90% probability) to 1780 (50% probability).

A 24/25 match means even less. 24/25: The 90% probable TMRCA is <=48 gen, >= 800 AD; 70% is <= 30 gen., >= 1260 AD; 50% is <= 21 gen., >= 1480 AD.

Matching 23/25 may not illuminate your genealogical studies at all, as your common ancestor may have preceeded records with surnames. 23/25 or worse: You share a common ancestor, but he may not have lived within a genealogic time frame

Looking at this in terms of generations, instead of years, the match of 23/25: 90% TMRCA is <= 67 gen., >= 330 AD; 70% is <= 46 gen., >= 860; AD; 50% is <= 34 gen., >= 1160 AD.

While a 22/25 match means even less. 22/25: 90% TMRCA is <= 86 gen., >= 140 BC; 70% is <= 61 gen., >= 480 AD; 50% is <= 47 gen., >= 830 AD.

Input from Ralph Taylor and Lalia Wilson

Saturday, August 8, 2009

What Does a 12 Marker Match Mean?

Here are some thoughts from Ralph Taylor on 12-marker Matches:

About 12-marker matches, there isn’t a lot to say. There are only three possibilities:

A perfect 12/12 means you share a common ancestor. But that ancestor may be many centuries in the past. The 90% probability level includes the past 60 generations (dating to as early as 510 AD); the 70% level includes the past 31 generations (as early as 1235 AD; and the 50% level (as likely to be low as high) includes the past 18 generations (as early as 1560 AD).

11/12 is inconclusive. Comparison of more markers is needed to draw any conclusions. If you are the one with only 12 markers tested, you should upgrade to more markers.

10/12 or worse excludes sharing a common ancestor within several thousands of years.

That’s cold, but true. 12 markers are considered sufficient to exclude sharing of a common ancestor, but not to include it.

Now, Lalia's interpretation... This means quite simply that if you match someone with the same surname 12 for 12, it suggests that you share that surname. However to trace your ancestry, you are going to need to test more markers and match more markers! (About which we will have more information in a future blog.)

If you do not share the same surname, or a variant of the surname, then a 12/12 match means that you likely come from the same general gene pool, such as the British Isles, and means nothing more.

We will have some forthcoming blog posts about higher levels of matches.

Good luck with your own genetic genealogical projects!


Terminology Used in Genetic Genealogy


Here are some terms that Ralph Taylor provides to help you understand your reading of articles and blog posts about genetic genealogy.

MRCA: The most recent common ancestor shared by two or more persons with a DNA match. We are concerned only with the most recent, because preceding ancestors will also be shared.

TMRCA: The probable time to the MRCA, expressed in generations.

Probability level: The cumulative probability, expressed as a percentage, that a MRCA lived within the specified number of generations. Here, we give three probability levels, 90%, 70%, & 50%. 90% means the chances are 9/10 the TMRCA is <= the given number; 50% probability is as likely to give a low TMRCA as a high one.

Genealogic time frame: A time for which it is feasible to specifically identify an ancestor, generally from about 1350 AD to the present.

Generations, length of: This is an estimated average of 25 years, developed from 18th and 19th century America statistics. We use the estimate to convert generations to common dates. Other societies may have had a different generational length -- either longer or shorter.

<=: Means less than or equal to, the maximum generations number for that probability level

>=: As applied to dates, means no earlier than the given date.

Monday, August 3, 2009

Key Dates in Taylor Genealogy


We are going to have several posts authored by project co-administrator Ralph Taylor, with input from project head, Dr. Leigh Taylor, and from me. We start with some basics that impact every Taylor, key dates.

1066 AD: Norman Conquest of England , bringing the word “tailleur” for a maker of clothing into the language. One Taylor line claims descent from an officer in the victorious army.

1350 AD: The approximate time surnames came into general usage. Most Taylor families first used the surname then; before that, it was “Robert, the town tailor”, not “Robert Taylor”. (Similarly with Carpenter, Cooper, Plummer & Smith.)

1607 AD: Founding of Jamestown , Virginia , the first permanent English settlement on the American continent. This event began English Taylor migration to what would become the United States of America .

1700 AD: The beginning of Scots Irish migration to America , bringing Taylor families from Ireland , particularly the Ulster & Armargh provinces. Taylor descendants hail from the Cameron clan.

1709 AD: Beginning of Palatine migration to America . Some Germanic Schneider families anglicized their name to its English equivalent, Taylor .

1763 AD: France ceded most of its North American territory to Great Britain , opening the way for British migration to Canada . We begin to see Taylor spelled as pronounced in various areas of the county: Tayler, Tyler, Tolliver, Taliaferro (Italian), Tailor, Taler, etc.

1788 AD: Britain established its first settlement in New South Wales , Australia . Many of the early settlers were convicts from England .