Minggu, 23 Januari 2011

King Tutunkhamun's DNA in doubt


Can we be sure which mummy was the daddy? When a state-of-the-art DNA analysis of Tutankhamun and other ancient Egyptian royals was published last year, its authors hailed it as 'the final word' on the pharaoh's family tree. But others are now voicing doubts.

The analysis of 11 royal mummies dating from around 1300 BC was carried out by an Egyptian team led by Egypt's chief archaeologist Zahi Hawass. The project was overseen by two foreign consultants, Albert Zink of the EURAC Institute for Mummies and the Iceman in Bolzano, Italy, and Carsten Pusch of the University of Tübingen, Germany.

The researchers used the DNA data to construct a family tree of Tutankhamun and his immediate relatives. The study, published last February in the Journal of the American Medical Association (vol 303, p 638), concluded that Tutankhamun's father was the pharaoh Akhenaten, that his parents were brother and sister, and that two mummified foetuses found in Tutankhamun's tomb were probably his stillborn daughters – conclusions that have since become received wisdom.

But many geneticists complain that the team used inappropriate analysis techniques. Far from being definitive, the study is 'not seen as rigorous or convincing', says Eline Lorenzen of the Center for GeoGenetics at the Natural History Museum in Copenhagen, Denmark. 'Many of us in the DNA community are surprised that this has been published.'

...

To judge the quality of the team's results, Lorenzen and others are asking for access to raw data not included in the Journal of the American Medical Association paper – but Zink is reluctant to oblige, fearing the data would spark 'a lot of arguing' over technicalities.

However, Zink, Pusch and colleagues insist that they will soon be able to put any doubts to rest. They say they have also extracted the mtDNA that Lorenzen and others consider necessary for rigorous genetic analysis and are still working on the data. They hope to publish the results this year.

But the critics are still advising caution. 'When working with samples that are so well-known, it is important to convince readers that you have the right data,' says Lorenzen. 'I am not convinced.'

This is the paper they are referring to (Ancestry and Pathology in King Tutankhamun's Family, Zahi Hawass et al., JAMA. 2010;303(7):638-647. doi: 10.1001/jama.2010.121)

I don't understand what is the problem with 'arguing over technicalities'. That's the whole point of releasing as much data as possible, to make it easier for others to evaluate your conclusions. I don't understand why a scientist would want data to be hidden: perhaps it might make sense for nuclear scientists or virus experts to keep some data hidden, but why would Tut's DNA be hidden?

People who liked at Tut's alleged Y-STR values from screencaps have concluded that he belonged to haplogroup R1b; as this is a rare haplogroup in Egypt, and frequent in Europe, it has sparked debate about his origins. If the Y-STR values are legit, an alternative explanation is that the ancient DNA is not authentic but represents a European contaminant. In any case, I hope that as much data as possible about the case is released, so that everyone can make an informed assessment.

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