Well, the paper is finally out, New insights into the Tyrolean Iceman’s origin and phenotype as inferred by whole-genome sequencing. In case you don’t know, Ötzi the Iceman died 5,300 years ago in the alpine region bordering Austria and Italy. His seems to have been killed. And due to various coincidences his body was also very well preserved. This means that enough tissue remained that researchers have been able to amplify his DNA. And now they’ve sequenced it enough to the point where they can make some inferences about his phenotypic characteristics, and, his phylogenetic relationships to modern populations.
The guts of this paper will not be particularly surprising to close readers of this weblog. The guesses of some readers based on what the researchers hinted were correct: Ötzi seems to resemble mostly closely the people of Sardinia. This is rather interesting. One reason is prosaic. The HGDP sample used in the paper has many Northern Italians (from Bergamo). Why is it that Ötzi does not resemble the people from the region that he was indigenous to? (we know that he was indigenous because of the ratio of isotopes in his body) A more abstruse issue is that it is interesting that Sardinians have remained moored to their genetic past, enough so that a 5,300 year old individual clearly can exhibit affinities with them. The distinctiveness of Sardinians jumps out at you when you analyze genetic data sets. They were clearly set apart in L. L. Cavalli-Sforza’s The History and Geography of Human Genes, 20 years ago. One reason that Sardinians may be distinctive is that Sardinia is an isolated island. Islands experience reduced gene flow because they’re surrounded by water. And sure enough, Sardinians are especially similar to each other in relation to other European populations.
To get a better grip on his ancestry and predisposition to disease, Albert Zink, head of the Institute for Mummies and the Iceman in Bolzano, and his team sequenced Ötzi’s 3 billion base pair nuclear genome from a shard of hip bone. Their sequence covers more than 90 percent of the Iceman’s genome. Their team also analysed DNA preserved in Ötzi’s stomach in hopes of revealing the microbes that colonized his gut.
Zink says his team is keeping most of the results of these studies under wraps, pending publication. They had hoped to have the paper out in time for last week’s Mummy Congress and a television special called Iceman Murder Mystery.
His team plans to use the sequence to determine Ötzi’s status for genetic variations linked to diseases in modern humans, particularly arthrosclerosis. A full nuclear genome will also paint a more detailed picture of the Iceman’s ancestry and his relationship to present-day humans. Zink’s team will ask whether Ötzi is an ancestor of people living in Central Europe today, or whether he and his kin died out and were replaced by migrants from elsewhere, such as the Middle East. To buff up this analysis, they are analysing DNA preserved in the skeletons of other ancient inhabitants of central Europe.
~90 percent of a genome is way more than you’d need for some basic analysis and inference of relationships to contemporary populations. So what’s the big deal? No idea, but this tardiness makes me turn the needle up in terms of assuming that they found some interesting stuff. If it’s what you’d expect, why recheck and beef up your analysis with as much support as you can find? Of course, I hope that they found some interesting stuff, so I shouldn’t trust my own judgments in this area. My own suspicion is that they have found extensive genetic turnover over the past 6,000 years in Western Europe, and they are using modern and ancient samples to flesh-out their model. The two dominant paternal haplogroups in Europe today, R1a and R1b, are suspiciously scarce in the ancient DNA samples.