View Full Version : What is More Important for Determining Our Ancestry: Genealogy or Genetic Testing?

Thursday, October 22nd, 2009, 02:34 AM
Both studying family trees and genetic testing have some flaws, neither are 100% accurate it seems. For example in your family tree you might find a Germanic name for what was a Jew, and when you test genetically you only find a part of your ancestors (father's or mother's).

Nevertheless, what do you think it's better to define ourselves? What happens when genetic testing reveals something that doesn't correspond with genealogical conclusions? E.g. a Frenchman scores genetically Northern European.

Thursday, October 22nd, 2009, 02:50 AM
Ideally one should compliment the other. Neither is perfect though. Most individuals can only trace all their ancesteral lines back 10-15 generations or 300-400 years. It is possible to go back further but only for a relatively few ancestoral lines, the number of which doubles with each generation.

Genetic testing has its flaws in that persons of European race can test positive for non-European admixture. But whether that admixture is the result of common ancestors 50,000 years ago or within the last 500-years is unclear. The ancestors of the Amerindians crossed the Bering Strait 25,000 years ago, yet ancestoral genetic testing cannot differentiate between Asian/Siberian DNA & Amerindian DNA.

Thursday, October 22nd, 2009, 03:02 AM
I'm curious what is considered European by those tests. Are Turkish peoples who get tested classified as European or Middle Eastern or Asian? What about North Africans or Lebanese?

Thursday, October 22nd, 2009, 03:12 AM
It depends on the test. Some only differentiate between European (Caucasian, including Middle Eastern & North African), Asian (including Amerindian) & African.

Thursday, October 22nd, 2009, 04:31 AM
Would pre-Indo European survivors be Germanic then? Wouldn't their DNA be different from most other Germanic people? Their family tree could theoretically be Germanic for thousands of years back in time. That's why I think genetics is still not able to determine that, a family tree would be better still.

Sunday, October 25th, 2009, 04:25 AM
I'm curious what is considered European by those tests. Are Turkish peoples who get tested classified as European or Middle Eastern or Asian? What about North Africans or Lebanese?

It does depend on the test. A test that can't differentiate East Asians from Amerindians probably could not easily differentiate Europeans from Middle Easterners/North Africans. It certainly could not differentiate Greeks or South Italians from Anatolian Turks.

Friday, November 13th, 2009, 02:16 PM
Well for ancestry purely genealogy is better. But to define ourselves I think that a good Genetic Testing is better since we know that we heird half of the chromossoes from each parent randomly, meaning that our dna doesnt match exactly our ancestry.

Tuesday, November 17th, 2009, 12:30 PM
An interesting simulation (http://www.genetic-inference.co.uk/blog/?p=728) by Luke Jostins:

The probability of having DNA from all of your genealogical ancestors at a particular generation becomes vanishingly small very rapidly; there is a 99.6% chance that you will have DNA from all of your 16 great-great grandparents, only a 54% of sharing DNA with all 32 of your G-G-G grandparents, and a 0.01% chance for your 64 G-G-G-G grandparents. You only have to go back 5 generations for genealogical relatives to start dropping off your DNA tree. [. . .]

The number of genetic ancestors starts off growing exponentially, but eventually flattens out to around 125 (at 10 generations, 120 of your 1024 genealogical ancestors are genetic ancestors).