There's no way all the tribes descend from someone called Abraham who lived 2000 BC.
http://www.aish.com/societyWork/sciencenature/Abrahams_Chromosomes$.asp
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Can recent genetic research give some indication of the existence of the historical Abraham?Recent genetic studies of the Jewish people clearly indicate that the roots of the Jewish nation can be traced to the Middle East. This research confirms the geographical origin of the core of every major Jewish Diaspora community. (See: "Jewish Genes.")
Furthermore, the discovery of the "Cohen Gene" -- the genetic signature shared by the majority of Kohanim -- the Jewish priestly family worldwide, is an indication that this signature is that of the ancient Hebrews. (See:"The Cohanim - DNA Connection")
Based on the DNA of today's Kohanim, the geneticists have dated their "Most Common Recent Ancestor" to 106 generations ago, approximately 3,300 years before the present. This is in agreement with the Torah's written and oral tradition of the lifetime of Aaron, the original High Priest and founder of the Kohen lineage. Further genetic studies have found that the CMH-the Cohen Modal Haplotype-a haplotype of the MED (J) haplogroup-is not exclusive to Kohanim, and not unique to Jews. It is also found in significant percentages among other Middle Eastern populations, and to a lesser extent, among southern Mediterranean groups. A haplotype is a group of distinct DNA markers -- neutral nucleotide mutations, which when found together indicate a lineage. These particular markers were discovered on the Y-Chromosome, which is passed from father to son, without change, thus establishing a paternal lineage pattern.
All of the above is scientific fact, which has only become known in recent years. Using these findings as a basis, perhaps we can speculate and consider some implications of the findings.
If the CMH is the genetic signature of Aaron, the father of the Kohanim, it must also have been the genetic signature of Aaron's father, Amram, and that of his father, Kehat, and of his father, Levi. Levi's father was Jacob who also must have had the CMH as his Y-Chromosome genetic signature, as did his father, Isaac.
Thus we arrive at Abraham. Abraham was only seven generations removed from Aaron, a matter of a few hundred years. Genetic signatures change slightly only over many generations. Thus, it is very reasonable to assume that the CMH, the most common haplotype among Jewish males, is therefore also the genetic signature of the Patriarch Abraham."
Blacknad.
