Archaeologists in Peru have identified a rare chromosomal condition in an infant buried about 1,600 years ago in the Palpa Valley, Live Science reported. DNA analysis confirmed that the child, a female infant, had an extra copy of chromosome 13, known as trisomy 13 or Patau syndrome, according to a study published Nov. 9 in the journal PNAS. The skeleton had a very small skull and a single eye socket in the middle of the face, traits that match modern clinical descriptions of cyclopia, a lethal condition that occurs when the front of a fetus's brain fails to divide into left and right hemispheres. "The cause of the malformation was present at fertilization, but manifestation occurs around the fourth to fifth week in utero, when the frontal lobe of the brain has to divide," first author Elsa Tomasto-Cagigao, an archaeologist at the Pontifical Catholic University of Peru, told Live Science. Cyclopia occurs in about 1 in 100,000 births. Trisomy 13 is a major chromosomal cause, though only a small share of trisomy 13 cases involve cyclopia.
The skeleton was found alongside a second infant inside a ceramic urn at Jauranga, near the Nazca Lines, among several dozen burials dated to the Middle Nazca, or Nasca, period (A.D. 325 to 440). "We cannot really say how long this individual survived," co-author Lars Fehren-Schmitz, an anthropologist at the University of California, Santa Cruz, told Live Science. "The burial of this infant suggests that the Nasca treated this individual in death like most other infants." Siân Halcrow, a bioarchaeologist at Durham University who was not involved in the study, said that, to her knowledge, this is the first archaeological example of the developmental abnormality, and that the estimated age at death suggests the infant may have survived for several weeks or months. "This raises important questions about how infants with profound congenital differences were cared for and treated in past societies," she said.
Urn burial was a common Nazca practice. The infant with cyclopia was at the bottom of the jar, and the second female infant, who had no skeletal abnormalities, was on top. "Nevertheless, it appears that they were interred in a single event," Tomasto-Cagigao said. Genetic analysis showed the two infants did not have the same mother. A burial of two infants in one urn is unusual for this culture, the researchers said, but there is not enough evidence to conclude that the child with cyclopia was given a different type of burial. "The fact that the individual was buried with a 'healthy' individual in a regular cemetery, without any special grave goods, suggests that, to some extent, the individual was not treated differently in death, even though it had such a rare condition," Fehren-Schmitz said. "It was neither 'excluded' because of it nor treated in a 'special' way."
In some ancient Andean societies, people with disabilities took on special roles, including religious ones. "If that reflects Nasca society as a whole, we can't say based on one case," Fehren-Schmitz said, "but it does reflect the community this infant was part of, even if only briefly." While trisomy 13 is associated with advanced maternal age, he said it is not clear whether that was the case here. The verified finding is a genetic diagnosis, a shared urn, and a burial that, on the available evidence, looks ordinary rather than exceptional.