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Archive for October 30th, 2008

The Y-Chromosomal Footprint Of Phoenicians Throughout The Mediterranean

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The Phoenician Alphabet

The Phoenician civilization is understood to be the dominant maritime trading culture between the period of 1550 BC to 300 BC. While they were based out of the Levant, their city-states were spread all across the Mediterranean. The golden age of Phoenician culture and seapower is usually placed around 1200–800 BC. When Cyrus the Great conquered Phoenicia in 539 BC, he divided the Phoenicians into four vassal kingdoms by the Persians: Sidon, Tyre, Arwad, and Byblos. Each flourished, building fleets for the Persians against the Greeks. But their autonomy as distinctly Phoenician people declined after this. The lasting and most important cultural legacy of Phoenicians on modernity is their alphabet. It is generally thought that their alphabet is the ancestor of most modern alphabets.

Okay enough of a history lesson, a team of researchers developed a set of algorithms to detect the subtle genetic impact of historical population migrations. They’ve tested out their formulas on 1,330 men in hopes that they’ll be able reveal the genetic legacy of the Phoenicians. Specifically, they have made a new set of tests that seek out patterns in genetic signatures of modern men. They’ve published their research in the the American Journal of Human Genetics under the title, “Identifying Genetic Traces of Historical Expansions: Phoenician Footprints in the Mediterranean.”

The team sampled Y chromosomes of men from historic Phoenician trading centers in the Mediterranean regions of Syria, Palestine, Tunisia, Morocco, Cyprus, and Malta. After genotyping them, they compared them on 11 STRs and 58 Y-SNPs markers. They weeded out background variation from previous Neolithic migrations, and singled out more widespread Greek colonization events from isolated Phoenician expansions, such as the Phoenician colonization of Tunisia.

The Phoenician Genetic Footprint In the Mediterrenean

The Phoenician Genetic Footprint In the Mediterrenean

The authors were able to detect a half dozen haplotypes and they call them Phoenician Colonization Signals (PCS). PCS3+ is calculated to be the strongest Phoenician-colonization candidate. It is tightly associated with the SNP haplogroup E3b, but it does not show the wide geographic coverage that the other PCS+s demonstrate. Both PCS1+ and PCS2+ score well, although not as strongly as PCS3+. The excess of haplogroup J2, and PC1+ to PS3+ in coastal Tunisia, the site of Carthage, compared to inland Tunisian populations is exceptionally significant, and suggests that the Roman destruction of Carthage did not eliminate the Carthaginian gene pool. So the presence of these seven related genetic lineages in places around the Mediterranean Sea, tell us that where Phoenicians had lived and persisted genetically.

These lineages suggest that the Phoenicians contributed their genes to at least six percent of modern populations of historic Phoenician trading outposts. In fact, one boy in each school class from Cyprus to Tunis may be a direct male-line descendant of the Phoenician traders.

Of course, since this is only a Y-chromosome test, we’re only getting part of the genealogical history. If a Phoenician man fathers only daughters, his Y-chromosome lineage dies out. That means tests likes these can only say something when there’s an unbroken male line in that area. It is certainly possible that more people from Cyprus to Tunis have a Phoenician heritage. Dienekes, a Greek, has a scathing criticism of the paper. This paper explicitly says they didn’t try to seek out Greek expansion but Dienekes outlines six shortcomings, related to Greek expansions, that the paper didn’t factor that would affect these conclusions — he ends his post saying,

“Is there anything of value in this paper? Well, it’s a good idea to try to correlate Y-chromosome distribution with historical rather than pre-historical events. Too bad the authors botched the job, but their paper can at least serve as a reference point for how not to go about doing it.”

    Pierre A. Zalloua, Daniel E. Platt, Mirvat El Sibai, Jade Khalife, Nadine Makhoul, Marc Haber, Yali Xue, Hassan Izaabel, Elena Bosch, Susan M. Adams, Eduardo Arroyo, Ana María López-Parra, Mercedes Aler, Antònia Picornell, Misericordia Ramon, Mark A. Jobling, David Comas, Jaume Bertranpetit, R. Spencer Wells, Chris Tyler-Smith, The Genographic Consortium (2008) American Journal of Human Genetics. DOI: 10.1016/j.ajhg.2008.10.012

Written by Kambiz Kamrani

October 30, 2008 at 2:43 pm

The Mitochondrial Lineage Of Ötzi Is Not Like Other Europeans

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Last month I was excited to share some research about the chemical composition of Ötzi, the 5,000 year old Tyrolean Iceman that has captured my attention for quite sometime. Today, I’m even more excited to share that the complete mitochondrial genome of Ötzi has been sequenced using a combination of PCR amplification and 454 sequencing. The research has been published in Current Biology. You can find it under the title, “Complete Mitochondrial Genome Sequence of the Tyrolean Iceman.”

I’ve covered the details behind Ötzi before. I’ll give you a quick run down in case you forgot or never knew about him. Ötzi is the name given to mummy discovered on September 19th, 1991, around 3,270m above sea level, in the Eastern Alps near the Austro-Italian border. His remains were dated to be , 5,350–5,100 years old, and was remarkably preserved because of the cold climate. We have an idea what his last meal was and what he wore. He’s thought to have been around 46 years old, his fertility has been questioned, and his cause of death seems to have been rather horrific — severely wounded by an arrow and some blunt force trauma to his face.

Previous researchers have sequenced some of his mitochondrial genome, specifically the hypervariable segment (HVS-I). Two nucleotide transitions, at positions 16224 and 16311, indicate that Ötzi’s mtDNA belonged to haplogroup K, a subclade of the major west Eurasian haplogroup U. The authors of the new Current Biology paper decided to completely sequence the mitochondrial genome of Ötzi using 454 pyrosequencing technology. They’ve compared the sequence to 115 published complete mtDNA sequences from modern individuals, and constructed a phylogeny of the K haplogroup.

The sequencing run seems to have been rather uneventful. I’ve covered 454 technology before, but to recap it is sequencing by synthesis, which involves template DNA being immobilized, and solutions of each nucleotide added. They hybridize to their complement at the first unpaired base of the template. The hybridization reaction lets off light, because the polymerase enzyme is paired with another other chemiluminescent enzyme. A high resolution photo is taken and any remaining unbound nucleotide is removed and then another wash of another base is made. With the array approach developed by 454, it is possible to generate over 100 million nucleotide data in a 7 hour run with a single machine.

The authors reported they made 45,829 reads, but only 42,695 reads, or 93.2% of the total, were usable. Several gaps in the mitochondrial genome were observed, so PCR products were cloned into vectors and sequenced with conventional Sanger technology. When compared with the revised Cambridge Reference Sequence (rCRS), the consensus sequence showed 30 mtDNA transitions. A phylogenetic comparison was made to all 115 haplogroup K complete sequences currently available. The authors confirm that Iceman’s sequence falls within haplogroup K.

But, transitions at positions 3513 and 8137 on the Iceman’s mitochondrial genome indicate that his maternal lineage belongs a K1 subhaplogroup but not to any of the three subclades into which K1 is currently further subdivided (K1a, K1b, and K1c). The authors conclude that the Iceman’s mtDNA, belong to a novel branch of K1, not yet identified before. They’re calling it K1ö.

I’m not gonna get into much of a discussion about contamination because the samples were taken from thawed tissue from the mummy’s rectum. Many lines of evidence show that there was a lot of endogenous mtDNA that woulda muddled out any contaminating DNA and the results reconfirm the previous HVS-1 results. Anyways, this is the oldest complete H. sapiens mtDNA genome generated to date. The results show that as the frequency of genetic lineages change over time, due to genetic drift, some variants die out. Based upon the mtDNA, it is highly unlikely that Ötzi has any modern day maternal relatives… unless we sequence more than 115 haplogroup K carriers.

    Luca Ermini, Cristina Olivieri, Ermanno Rizzi, Giorgio Corti, Raoul Bonnal, Pedro Soares, Stefania Luciani, Isolina Marota, Gianluca De Bellis, Martin B. Richards, Franco Rollo (2008). “Complete Mitochondrial Genome Sequence of the Tyrolean Iceman” Current Biology, DOI: 10.1016/j.cub.2008.09.028

Written by Kambiz Kamrani

October 30, 2008 at 11:43 am

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