Originally posted by Baal Melqart
@Putty, it interests me how you seem to understand the history of these genes so well. Any link you might have that goes through the basics?
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There are plenty of links and sources in terms of genetic studies, but it's better to understand the basics first before looking at them, population genetic studies are divided into two types, recent ancestry (The past 2000 years or so) and deep ancestry (This goes back to our human origins in Africa beyond 50,000 years ago).
Before looking at what genetic studies have to say, as humans we carry 46 chromosomes, these 46 chromosomes are in 23 pairs (23 + 23 = 46), 22 of the 23 pairs are part of the non-sex chromosomes, these are called the Autosomal DNA which determines everything about us from looks, to shapes, to diseases, to whatever we inherit from our ancestors from all sides, and when I say from all sides I mean from both of your parents who also inherited from their parents (Your Grandparents) who inherited from their parents (Great Grandparents), so on, so you basically carry about 50/50 from your parents, and this 50/50 may be 25/25/25/25 when you look back to your grandparents (These numbers could be different, I'm just giving a general example), these percentages eventually get smaller as you keep going down to the deeper ancestors, of course by the time you go back beyond a 1000 years it would be too diluted to track further, in other words Autosomal DNA is most useful for the last 10 generations and this is the best test to determine recent ancestry and population comparison, so based on Autosomal DNA, they're able to tell the difference between a Saudi Arab and an Indian for example, it's also worthy to mention that the Autosomal DNA is about 96% of our DNA.
The 23rd pair of chromosomes are the sex chromosomes, this is what differentiates between males and females, the females carry XX while the males carry XY, for the males the Y-Chromosome is very important in terms of deep ancestry which takes us back all the way to Africa over 50,000 years ago, it's like a last name that's passed down from fathers to sons so the Y-DNA is only exclusive to males (Females cannot test for it since they don't carry it), this is called the paternal line, as for the maternal line, that can be traced through the mtDNA (Mitochondrial DNA), Mitochondria are cell inclusions of which there are about 1000 per cell, they are mini power packs with their own DNA separate from the nuclear (autosomes and sex chromosomes) DNA, this is passed down from mothers to daughters, the sons can also receive it from their mother and carry it but they cannot pass it down, so this is what we call the maternal line that can trace us back to our maternal ancestor in Africa over 150,000 years ago.
Now that we have all the basic information, we know that Autosomal DNA tests all your sides and determines what population you relate to today, but the down side is it cannot go back very far in human history, while the Paternal/Maternal lines (Y-DNA/mtDNA) take us back over 50,000 years ago and all the way back to our roots in Africa which helps with the migration path, but the downside is you're only tracking one line (Two lines actually since one is paternal and the other is maternal).
The Dodecad site uses Autosomal DNA in the analysis, so as you can see you have percentages of what these populations carry, the person who runs this site also accepts samples from people who have done their DNA tests, I submitted my sample to him for example so I'm in the study, if you look at this spreadsheet, my ID is DOD037:
https://spreadsheets.google.com/ccc?key=0ArAJcY18g2GadG0zRlpFTjVnemJjU0d2MUtJSkMzNGc&hl=en&authkey=CP-9p_wC#gid=0
So as you can see he built a very big nice database of all these people that have submitted their data and all these results correspond very well to their backgrounds assuming they're not of mixed ancestry.
As for the deep ancestry, there are things called haplogroups, these are basically mutations that happen as time passes, the earliest ancestor is considered the Y-Chromosonal Adam (Not the religious Adam), he's estimated to have lived around 80,000 years ago in East Africa and everyone on Earth today comes from his line, to make things more clear he was not the only man during his time, but for whatever reason his line is the only one that survived, so no matter what we look like or whatever shape or form we come in, we're all one huge family that come from this man, as his descendants kept on growing they kept passing his Y-DNA lineage down, in very super rare occasions there are mutations that happen to the Y-DNA, and once mutation happens, all the descendants of this person carry the same exact mutation, so for example let's assume we have the following:
Father (A)
Son 1 (A), Son 2 (A), Son 3 (A1)
Son 3 developed a mutation as you can see, like his other brothers, he also inherited the (A) from the father, but he also mutated to (A1), therefore all his children will be (A1) like him, but the children of his siblings will be (A) only, do you see what I mean? In other words our Y-DNA has mutated many times and the mutation helps us identify the migration path our paternal line took, the maternal line (mtDNA) is the exact same thing but through the mother of course, read the following links to understand more:
http://en.wikipedia.org/wiki/Y-chromosomal_Adam
http://en.wikipedia.org/wiki/Mitochondrial_Eve
So if we want to be relevant to the topic, the Gulf and Bedouin Arabs mostly carry haplogroup J1c3d, if we trace this back to Africa, this is how many mutations happened:
J1c3d (In Levant or Anatolia 5000 years ago)
J1c3 (In Eastern Anatolia 5000 to 10,000 years ago)
J1c (In Eastern Anatolia 10,000 years ago)
J1 (In Eastern Anatolia 10,000 to 20,000 years ago)
J (In Near East 20,000 to 30,000 years ago)
IJ (In Near East 30,000 to 40,000 years ago)
IJK (In Near East 40,000 to 50,000 years ago)
F (In Near East 50,000 to 60,000 years ago)
CF (In Near East 60,000 to 70,000 years ago)
CT (In Eastern Africa 70,000 to 80,000 years ago)
BT (In Eastern Africa 80,000 years ago)
Adam (In Africa 80,000+ years ago)
The years are just example estimates on educational timelines, so based on that we estimate that the Arab men in Arabia mostly come from a group that lived in the Levant area around 5000 years ago, this specific lineage is also very common in Jews, that means that the Jews and Arabs that carry this lineage (J1c3d) share an ancestor (The man that developed this mutation in the Levant area 5000 years ago).
I know this might be a bit complicated now, but as you keep reading more on this stuff you'll get the hang of it, it's not rocket science that's for sure, and I hope MediaWarLord learns a thing or two here
Edited by Putty19 - 05-Apr-2011 at 04:44