Genes-R-Us — The tree of ‘Adam’ and ‘Eve’
Posted: Wednesday, October 5, 2011 5:02 pm
Last week you met two special “trees” that can be used to decode your maternal and paternal direct lineage. Scientists construct these haplogroup trees using slowly-changing DNA “letters” (or SNPs) from your “genetic instruction book” (or genome). Everyone has a maternal signature inscribed into their mitochondrial DNA (mtDNA), while only males have a paternal signature inscribed into the Y-Chromosome (Y-Chr).
Your mtDNA haplogroup traces your mother’s mother’s mother’s … mother’s line. The Y-Chr haplogroup traces your father’s father’s father’s … father’s line. Obviously, you have lots of other ancestors — but these are the two direct lines that you can access through DNA analysis.
The mtDNA and the Y-Chr haplogroup trees are not constructed exactly like a family tree. A family tree starts from the present and goes back in time from you to your parents to your two sets of grandparents, and so on. Haplogroup trees are constructed in just the opposite way; they start out in the past and march forward in time.
Haplogroup trees starts with an ancestral “Adam” or “Eve” and then split off into sizeable groups of individuals that can be tagged to a specific place and time. Ancestral “Adam” and “Eve” are not the biblical Adam and Eve for a number of reasons. For one reason, ancestral “Eve” predated ancestral “Adam” by many thousands of years. What this means is that everyone who is alive today is a direct descendant of the same one man and the same one woman — although they did not “know” one another in the biblical sense or coexist in time.
This does not mean that they were the first humans but it does mean that other male and female lines died out for some reason (for example, a worldwide flood could do this if only one family survived). A more genetic way to say this is that all “Mommy” and “Daddy Signatures” can be traced to these same two individuals. Changes in our SNPs found in our mtDNA or Y-Chr track the historical path from ancestral “Adam” to us and from ancestral “Eve” to us.
A subgroup of people is represented by a split off the haplogroup tree into a new but connected migratory line of people. Groups are labeled with a capital letter followed by some combinations of numbers/letters that provide more detail. There are many people-group designations but every single group can be traversed back through various splits back to ancestral the “Adam” or “Eve.”
As a female, I have only direct access to my mtDNA haplogroup — which also matches my birth mother’s mtDNA haplotype. I have found no surviving males in the direct line of my birth mother. I was able to access my paternal lineage through my birth father. Although the example below is specific to me, it illustrates what you can learn about your ancestry.
My maternal mtDNA haplogroup is J1c2. J tracks the introduction of farming and herding into Europe around 7,000 years ago from the Middle East. An estimated 10-25 percent of the Middle East, depending on the region, is J1 — consistent with the ancient roots of J1 in that region. The “c2” part of the J1c2 verifies my mother’s Celtic roots. This is completely consistent with her claims of Irish lineage.
My paternal mtDNA haplogroup is X2b. X is found throughout the Northern Hemisphere but is exceedingly rare nowadays, except for two seemingly unrelated people groups: the Druze of the Middle East and a several Canadian North American Indian tribes. Based on additional genetic evidence, my paternal mtDNA haplogroup appears to be from the Micmac Indian tribe in Nova Scotia/New Brunswick.
This was a very exciting surprise.
My paternal Y-Chr haplogroup is R1b1b2a1*. Half the men of Western Europe share the R1b1b2 portion of my father’s paternal haplogroup. It seems to be particularly common in the Irish, British, French and the Basques. No huge surprises here.
Note that haplogroups are being revised and extended as scientists are able to sequence more genomes from both from large groups of modern humans and the unearthed remains of ancient humans.
Although we may fancy ourselves as disconnected from the historical past, here we find a map inscribed in our very cells with a direct line to our ancestors. How awesome is that!
Editor’s note: Nancy Miller Latimer has worked in scientific research and development for 27 years. She blogs at neuronalbeauty.blogspot.com.
Published in The Messenger 10.5.11