The HIrisPlex DNA analysis system was recently recreated for modern forensic research, but the researchers have now shown that this system is sufficiently robust to successfully work on older and more degraded samples from human remains such as teeth and bones. The system looks at 24 DNA polymorphisms (naturally occurring variations) which can be used to predict eye and hair colour.
In their article, ‘Bona fide colour: DNA prediction of human eye and hair colour from ancient and contemporary skeletal remains’, the researchers examined the remains of Polish General Wladyslaw Sikorski (1881 to 1943) confirming his blue eyes and blond hair.
For medieval samples, where DNA is even more degraded, this system was still able to predict eye and hair colour (for the most degraded DNA samples eye colour alone), identifying one mysterious woman buried in the crypt of the Benedictine Abbey in Tyniec near Kraków, sometime during the 12th-14th centuries, as having dark blond/brown hair and brown eyes.
In another section the researchers describe the results from two further medieval samples:
Samples S25 and S26 came from two skeletons revealed during conservation work conducted in the Church of St. Andrew in Kraków in 2011. The church of St. Andrew was built between 1079 and 1098, and represents a great example of the Romanesque style. Two medieval skeletons were found under the floor between the chancel and the nave of the church. Based on historical markers the grave was dated to originate from the 14th century. Further anthropological examinations indicated that the S25 male died at the approximate age of 60, whereas the S26 male was approximately 75 years old at the time of death. It is alleged that the skeletons belong to members of the Tęczyński family, representing noble Polish magnates of medieval times. The tooth collected from the deeper burial (S25) was found to be seriously affected by decay, which was reflected by a very low DNA concentration (3 pg/µl) and incomplete autosomal and Y chromosome STR profiles (NGM and Yfiler). Complete mtDNA HVI and HVII profiles were generated in both teeth (data not shown). From these data it was possible to conclude that both skeletons are of male origin and are unrelated in both maternal and paternal lines. From the partial HIrisPlex profile ascertained from S25 we successfully inferred blue eye colour (P = 0.899, accuracy of 95.6%), but hair colour could not be inferred because of missing genotypes at three DNA variants (N29insA, rs1805005, rs2228479). The sample S26 revealed a prediction of blond hair colour (P = 0.784) together with a light hair colour shade (P = 0.918) concluding that the individual had light blond hair (accuracy of 69.5%). Eye colour prediction of S26 revealed blue eyes (P = 0.919, accuracy of 97.4%).
Dr Wojciech Branicki, from the Institute of Forensic Research and Jagielonian University, Kraków, who led this study together with Prof Manfred Kayser, from the Erasmus University Rotterdam, explained, “This system can be used to solve historical controversies where colour photographs or other records are missing. HIrisPlex was able to confirm that General Wladyslaw Sikorski, who died in a plane crash in 1943, had the blue eyes and blond hair present in portraits painted years after his death. Some of our samples were from unknown inmates of a World War II prison. In these cases HIrisPlex helped to put physical features to the other DNA evidence.”
The researchers have noted that the tests so far are believed to be more accurate in determining eye color over hair color. They conclude that the HIrisPlex system “will soon become more widely used in genetic studies of human remains in evolutionary, anthropological and forensic investigations.”
The article, ‘Bona fide colour: DNA prediction of human eye and hair colour from ancient and contemporary skeletal remains’, is published in the open access journal Investigative Genetics. Click here to read their paper.