Mapping my YDNA flow in Africa

I’ve spent the past week and a bit looking more closely at the YDNA I inherited from my father’s male line. It’s like returning to the original genealogical records you use in your research. You come back to them with more knowledge, a more seasoned eye and a better understanding of what you are looking at…and can usually pick up something new.

So, as I learn more about genetic inheritance and develop more finessed  genetic genealogy working practices, I keep returning to my Genebase YDNA and mtDNA results. What I have learn along the way has enabled me to make better sense of my test results. It has also enabled me to make better informed, educated, theories (yes, that is a rather nice way of saying I’m guessing…even if it is an educated guess). And, of course, I’m deeply appreciative of the patience instruction and advice I’ve been given by my genetic genealogy mates.

I’ve made no secret of my love for the Genebase testing service. It was the right DNA tool choice for what I wanted to accomplish. It has been worth every bit of the 4-figure sum I have spent sequencing  and analysing 90% of my YDNA and mtDNA sequence.

I’ve said it before and I’ll say it again. This isn’t a DNA testing service for everyone. There are no quick and easy pie charts that provide ethnic breakdown percentages. You have to work these out for yourself. Sometimes, with this service, you have to work hard in order to interpret the results this service provides. It’s part of what I really like about the service. When you’re forced to work with data of any kind, you have to understand what the data is, how it’s compiled, what it relates to…and ultimately what it means.

The image below gives you an idea of some of the information provided.

Rapanui

Image 1. Click for larger image

I’ll break the information contained in the image above:

This is a small fraction of the data returned by Genebase for my YDNA. The image shows results for a sliver of my YDA: Y-STR markers DYS19a, DYS389i, DYS389ii, DYS390, DYS391, DYS393. By themselves, Y-chromosomal DNA (Y-DNA) short tandem repeat (STR) markers from a Y-DNA test do not have any particular meaning. The value of testing YDNA STR markers comes from creating a YDNA signature (haplotype) with them and comparing that YDNA signature to others in a database. They are useful for genetic genealogy because your YDNA signature distinguishes your paternal lineage from others.

Like any other similar DNA testing service, Genebase compares markers to specific global populations. It groups these results by generational difference (the number of generations you’re likely to be distant from a genetic match). That’s a very over-simplified explanation.  Hopefully, you get the picture.

In the image above, you can see the populations associated with the YDNA STR markers I’ve cited. The report lists matches from a Generational Distance (GD) of 1 to 5.

For transparency, I’m providing a longer abridged list of matches. Trust me, there is a long, long list for these particular markers spread of 6 degrees of genetic distance. That’s a whole lot of cousin action going on:

A partial list of African genetic tribal matches with a GD of 1 and 2.

Image 2. A partial list of African genetic tribal matches with a Genetic Distance of 1, 2 and 3. Click for a larger image.

So back to Image 1 and what it represents:

I’ll get the most obvious one out of the way first – the Rappanui of Easter Island. No, I am not a direct descendant of these people. They are my genetic cousins. Some unknown male ancestor carried my father’s paternal YDNA from Africa (most probably eastern Africa) to Eastern Island. No one knows where the Easter Islander’s ancestors arrived from within the Pacific Region.  That is still hotly debated. However, scientists estimate that humans arrived in Eastern Island around 400CE (Pioneers of Eastern Island http://www.pbs.org/wgbh/nova/ancient/pioneers-of-easter-island.html). Basically, these YDNA markers  that I carry left Africa en route to Easter Island an inconceivably long time ago.

easter island-3

“The middle of nowhere” pretty much sums up Easter Island’s location in the Pacific, marked by the “A” on this map. This beats my paternal grandmother’s mtDNA, which travelled from East Africa to the Aborigines of the Central Australian Desert.

What is pretty cool is the additional information that puts this result into context – something too few DNA testing services do. Genebase lets me know that there were 30 Rappanui tested. I match 2 of those 30 people at a GD of 1. These are my closet matches among the Rappanui. Scoot down to a GD of 2 and the number of Rappanui that share a genetic match with me for these Y-DNA markers jumps to 11 people from the 30 people tested.

Added to this information are research papers, scientific papers that cover the sample pool of DNA testers per region/county, etc. Sometimes, there is additional profile information about the the DNA tester – like which part of a country they resided in at the time they took the test.

For instance, here’s a study that came as part of my Rappanui results: 
Ghiani ME1, Moral P, Mitchell RJ, Hernández M, García-Moro C, Vona G. 2006.
Y-chromosome-Specific STR haplotype data on the Rapanui population (Easter Island)http://www.ncbi.nlm.nih.gov/pubmed/17506287 

Here’s a study on the Omani Arab population:
Alshamali F, Pereira L, Budowle B, Poloni ES, Currat M. 2009. Local population structure in Arabian Peninsula revealed by Y-STR diversity. http://www.ncbi.nlm.nih.gov/pubmed/19339785?ordinalpos=4&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

I’d provide a link to one of the African tribes in my match list. There isn’t one.Not in the match results for these markers at any rate.

So…back to Africa.

You can see the African tribes that share the same YDNA markers with me. Like the Rappanui, the greater the GD, the more people I match. When you begin to understand the large scale movements of people across the globe over eons of time, you begin to build a picture of how your YDNA or mtDNA has also travelled around the globe.

Looking at my GD1 results for this set of markers, the information about my African results are the same as my Rappnui results. I have more dataset matches with every increase in Generation Distance. At a GD of 1, I only have a handful of matches. A GD of 2 trebled the number of matching tribes and ethnicities.

Not all of these matches will be direct ancestors. Most, like the Rappanui, will be genetic cousins. Others will be direct ancestors. Given the number of times the Akele, the Puni and the Omani appear in a number of my YDNA markers, my team and I are very confident that I’m directly descended from all 3.

The next step was to build a map to indicate how my YDNA spread through Africa. Again, I’ve only been looking at the African part of my YDNA in this exercise. It’s the part of my identity I know the least about. So it make sense. I have an excellent understanding on the European parts of my YDA. My Near Asian, Middle Eastern, Central Asian, Southern Asian and Chinese results simply defy understanding. They are anybody’s guess at this point. From a personal as well as time and productivity standpoint, it makes sense to focus on the African parts of my YDNA at this point.

A working hypothesis on how my YDNA travelled through Africa

afr_asia_pol2

Let’s start with the blue region on the right hand side of the map. This is the origins of, well, me, in terms of my YDA. It all begins in the Horn of Africa. Like every other human being. At some point in the dim past, my YDNA left Africa and arrived in Yemen and Oman. Now you’d think that it would be found in the Arab populations in both places. Nope. Not a bit of it. In modern day Yemen, it’s only found in the Yemini Jewish population (so far). It’s found within the Arab population of Oman.

At a further point in time, that YDNA returned to Africa. The team is presuming it returned to the eastern part of Africa before heading north to Egypt and then across northern Africa (the pink region on the map). This journey is represented by the arrow marked “1”.

We think my YDNA travelled southeast – shown by arrow 2 – around the time as the same YDNA began making its journey northwards  (arrow 1). This southern journey seems to have stopped in Zambia. At the moment, I have no DNA matches with any of the data sets associated with countries to the south of Zambia on Genebase. Again, this is at the moment of writing this post.

My markers are indicating that something pretty interesting happened after the journeys shown by arrows 1 and 2. My YDNA flowed from northern Africa southwards into the African interior, terminating in Gabon and Zambia (the green and yellow arrows marked by ‘3’). The tribes I match indicate the route this journey took. These tribal cousins can be found in modern day Guinea-Bissau, Burkina-Faso, Ghana, Nigeria, Cameroon and the Democratic Republic of the Congo.

The 4th arrow shows a small journey from Gabon to Angola, home to more genetic cousins (at a GD of 3).

This seems to be as far south as my YDA has travelled within Africa. As science tests and studies the DNA from more African tribes, perhaps a fuller picture will emerge.

For now?  I’m getting a pretty good grounding of the overall picture of my African DNA…and the tribes and cultures it connects me to on that continent.

This is the value of this genetic testing service for me, personally.  I know how much of my DNA sequences have been tested. I have  crucial additional and contextual information about the data sets this service uses and population pool information. I know how many of these testers I match – and the degree of genetic difference between our matches – for all of the markers in the 90% of my genome that I’ve had tested. In some instances, I have general information about their geo-locations.  For what I aim to do, this is all invaluable information. And worth every penny.

The more commercial DNA testing services I’ve used don’t provide this level of information. I have no idea how much of my genome any of the big 3 testers have sequenced. Nor do I know the size of the dataset pools they have used to provide information about indigenous people tested (this is what gives you your ethnicity percentages). Nor do I have any idea how many people I match within those different indigenous data set pools to contextualize the percentages they give.

To be 100% fair, the big 3 commercial DNA testing companies are very upfront about what they do and do not provide when it comes to this level of information. I also don’t mind because I didn’t test with these services to receive this level of information. I used them to do deep work on my family tree via DNA matches on these services. I also use these testing services to meet and work with newly discovered cousins. So they have more than fulfilled their purpose. They too have been worth every penny…just for a very different reason.

It’s worth remembering that DNA testing services are tools. No one tool can do everything. Some are more suitable for certain jobs than others. I’m just grateful that each of them – each in its own way –  has given me more than my money’s worth.

 

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Filed under AfAm Genealogy, AfAm History, ancestry, Black History, family history, genealogy, Genetics, Race & Diversity

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