Pablo Carballada

Que ben vos preste!

Arquivos de Agosto de 2006

The longest journey

27 de Agosto de 2006 | Categoría: Familia | Mapa
Last year I submitted a DNA sample (a cheek swab) to collaborate with the Genographic Project. This is roughly a research study of the human journey, focused on the ancient migrations. I got the results then but I hadn’t had a deep look at them since.

The Genetics

We all have 22 matching pairs of chromosomes and a sexual pair (XX for females and XY for males). As you can see, the male pair don’t match, which means that there is no genetic recombination between them, unlike the other pairs or the female sexual pair.
And that’s the key to this investigation: Because I’m a male, I carry my mother’s X-chromosome (as a result of her parent’s X-chromosomes recombination) and my father’s Y-chromosome. But only this one is of any interest, because it is the same as my grandfather’s and my greatgrandfather’s … and so on.
The Y-chromosome (or most of it, the non-recombining region) remains unchanged and passed down from father to son (a pure male line) through generations, changed only by random mutational events.
These mutations are the genetic markers, they are inherited and tell us a complex story that can be traced backward in time.

Results: My Haplotype

My Y-chromosome was analyzed by STRs (Short Tandem Repeats), which are repeating segments of the genoma that have a high mutation rate. The location on the Y-chromosome of these markers is indicated in the image, with the number of repeats for each of my STRs.
Studying the combination of this STR lengths allowed researchers to place me in Haplogroup I, which reveals the journey of my ancestors (only direct male line!!).

M168 (31000-79000 years ago)

Not surprisingly, my oldest marker is M168, and first appeared in someone called by researchers “Eurasian Adam”, the common ancestor of all non-Africans, who lived at some stage between 31000 and 70000 years ago in East Africa.

His descendents migrated to the Arabian Peninsula and became the first homo sapiens to survive away from humanity’s birthplace, Africa. Why did they have to leave?
It was probably because there was a massive population growth in Upper Paleolithic era, and some people had to look for new hunting grounds somewhere else.

M89 (45000 years ago)

This marker is found in 90% of all the non-Africans, and defines Haplogroup F*.

These people followed the expanding grasslands to Middle East and beyond. But 40000 years ago, the climate shifted once again and became colder and more arid, the North-African grasslands reverted to desert, and for the next 20000 years, the Saharan Gateaway to Africa was closed.
They had two options: remain in Middle East or move on. They never could come back to Africa.
And so they did, some of them remained in Middle East and others travelled to Asia and then to East and West following the herds of atilopes, buffalos and mammoths.

M170 (20000 years ago)

But a smaller group decided to continue to the Northwest of Middle East, through Anatolia and the Balkans and eventually spread into Central Europe. They may have been responsible of the expansion of the Gravettian Culture, which eventually spread through Northern Europe. This marker defines Haplogroup I.

The man who gave rise to marker M170 was probably born 20000 years ago, somewhere in the Balkans, in one of the isolated refuge areas that people were forced to occupy during the last blast of the Ice Age. When the ice sheets covering most of Europe began to retreat 15000 years ago, his descendants colonized Northern Europe.

M253 (15000 years ago)

Some of the descendants of the M170 group, like many Europeans, looked for a place where they could survive until the end of the Ice Age. The man who carried the M253 marker for the first time was likely to belong to a group who travelled to the Iberian Peninsula and stayed there until 15000 years ago, when the ice finally began its slow retreat. These people left the peninsula and began to repopulate other parts of Europe that once were covered by ice.
They carried with them the unique genetic marker that defines Haplogroup I1a. This is the map of its European distribution.



Interpretation

When I got the results last year from Genographic I was only placed in Haplogroup I. I don’t belong to the commonest haplogroups in Western Europe, like Haplogroup R (R1b, more than 90%), but still… I thought it was normal, considering that Haplogroup I is not rare at all in Castile (Visigoths), Galicia (Suebi) and the Basque Country. But I went a little bit further and after a little research I was able to place me, according to my STRs results, in Haplogroup I1a, whose geographic distribution is quite far from my family’s area, as you can see in the map above.

There’s no need to say that the results surprised me at this point. I am not aware of any Scandinavian or Anglo-Saxon genetic input in my recent family history. I didn’t go through any deep genealogic research, but my family background seems to be quite common in the area, a rural countryside family that seemed to stay in the same place for ever…. My direct male ancestors have probably been living in Galicia (North-West of the Iberian Peninsula) for the last centuries. Their surname, Fernández, is very common in that part of the Peninsula and spread to the rest of Spain and Portugal from there, although this is not a valuable data, given that surnames were not inherited in Spain and Portugal until the 1300s-1400s.

The Vikings are meant to belong to this Haplogroup I1a. The Viking raids (800s-1000s A.C.) on Atlantic Europe might explain why the lineage can be found in the Brittish Isles and the continental Atlantic coast. They attacked the Galician coastal towns quite often and they even reached the country towns and burnt down Santiago in the X century.

But there is an alternative theory, more likely to be the real one: The suebi arrived to Gallaecia just after the Roman Empire collapsed. They were around 30000 and ruled the first European kingdom until they were defeated and conquered by the Visigoths. The suebi are supposed to belong to Haplogroup I1a, since they were a Germanic tribe which came originally from the Baltic shore.

Further research is ongoing.

8 comentarios

— Entrada anterior »