Genetic methods for sex determination shed some light on remains of Canary Islands' indigenous peoples

Archaeologists, anthropologists and forensic doctors use the bone measurements to know the sex of the skeletal remains they are studying in their investigations. However, this is not an easy job with ancient populations and when the complete skeleton is not available.

Researchers from the University of La Laguna (ULL) have applied a new technique based on genetic analysis to determine the sex of these bones of the indigenous peoples of the Canary Islands.

"We have determined the sex by genetic methods on 52 tibias belonging to a pre-hispanic population from the archaeological site of Punta Azul on the Island of El Hierro. The identification of 18 women and 34 men and the subsequent discrimination by combining various anthropometric variables, shows a high precision percentage of 94.2% in the diagnosis," Alejandra Calderón Ordóñez, researcher at the ULL and co-author of the article published in the Journal of Archaeological Science, told SINC.

The anthropometric variables include a series of measurements which, when combined in a mathematical formula, enable the most probable sex to be assigned to incomplete archaeological remains.

"The problem," adds the expert, "is that these functions vary between different populations and between the same populations over time, which means they are not always valid if they are applied to different populations to those for which they were carried out."

Sex determination through genetic procedures, on the other hand, has become a reliable reference technique given that it enables a correct diagnosis that can be compared with the measurable characteristics of male and female bones.

"Sex determination using this procedure is not always possible with all the bones discovered in an excavation given the state of preservation of the remains as well as the high cost involved in the procedure. Despite this, it is an essential tool," she adds.

Measuring tibias and analysing DNA

With the remains from Punta Azul, the researchers used a fragment of the amelogenin gene. As Calderón explains, this gene is present in the X chromosome and in the Y chromosome however, there is a small deletion -- a special type of chromosomal anomaly -- in X, which makes it ideal for sex determination by DNA amplification.

"Taking into account the actual characteristics of the DNA in old remains, an initial real time quantitative analysis of the mitochondrial DNA was taken to verify the state of preservation of the samples," she explained.

Only those in which the mitochondrial DNA could be amplified were selected to analyzed the amelogenin gene. It has been confirmed that if there is no mitochondrial DNA (multiple copies found per cell), the results obtained from a nuclear DNA amplification such as amelogenin are not very reliable.

The amelogenin was analyzedd in 53 of a total of 59 tibias and positive results were obtained in 52. All this shows that the sample was well-preserved.

Also, the tibias were measured and the results were combined with the previous genetic analysis. "This research shows that by studying the amelogenin, discriminant functions can be created for a specific population, which can later be applied to other remains from that same population with a higher degree of reliability," outlined the scientist.

The importance of this lies in proving the usefulness of the amelogenin gene as a standard for gender identification. This opens the door to the creation of new functions for various populations, with different bones and even improving some of those that already exist. The method could be applied to other populations of different ages and ethnic origins.