1,600-Year-Old Nazca Infant With One Eye Socket Had Trisomy 13

Researchers have identified the cause of a rare skull malformation in an infant buried about 1,600 years ago in southern Peru: an extra copy of chromosome 13, a condition called trisomy 13 or Patau syndrome. The skeleton has a single eye socket in the middle of the face, matching modern clinical descriptions of cyclopia. The team reported the finding in the journal PNAS on Nov. 9.

According to the authors, and to Live Science, which reported the work, a bioarchaeologist who was not involved in the study knows of no earlier archaeological example of this developmental abnormality.

What the researchers found at Jauranga

The infant was a girl. Her remains lay in a ceramic urn at Jauranga, an archaeological site in Peru’s Palpa Valley, where many of the geoglyphs known as the Nazca Lines have been found. Archaeologists recovered several dozen other burials at the site from the Middle Nazca period, A.D. 325 to 440.

The skull is very small and has one central eye socket, along with other changes to the cranial bones. Cyclopia occurs when the front part of the brain does not split into left and right halves. It can also alter the nose, leaving it missing or shaped like a tube above the eye. About 1 out of every 100,000 births is affected today.

Elsa Tomasto-Cagigao, an archaeologist at the Pontifical Catholic University of Peru and first author of the study, said the cause is present at fertilization, but the malformation appears around the fourth to fifth week in the womb, when the frontal lobe has to divide.

How scientists know it was trisomy 13

The team sequenced the infant’s genome from her remains. The data showed two X chromosomes, which is typical of a female, and an extra copy of chromosome 13. Trisomy 13 is a major chromosomal cause of cyclopia, although only a small percentage of trisomy 13 cases involve it.

The condition is linked to advanced maternal age in modern populations. Study co-author Lars Fehren-Schmitz, an anthropologist at the University of California, Santa Cruz, said it is not clear whether that applied to this infant’s mother.

The paper is titled “A Nasca-period perinatal burial reveals cyclopia associated with trisomy 13 in southern Peru” and appears in the Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2625042123).

A shared urn and what it says about care

A second female infant, with no skeletal abnormalities, was in the same urn. The child with cyclopia lay at the bottom and the other on top, and the researchers think both were placed there in a single event. The genetic analysis showed the two did not share a mother.

Burying two infants in one urn is unusual for this culture, according to the researchers, but they say the evidence is not enough to conclude that the child with cyclopia received a different kind of burial. Urn burial itself was a common practice for infants in the Nazca period.

Fehren-Schmitz said the lack of special grave goods and the burial next to another infant in a regular cemetery suggest the child was not treated differently in death. In his words, she was neither excluded nor singled out.

What is still unclear

Fehren-Schmitz said the researchers cannot say how long the infant survived. Siân Halcrow, a bioarchaeologist at the University of Otago in New Zealand who was not part of the work, noted that the team’s estimate of the age at death suggests she may have lived for several weeks or months. Halcrow said that raises questions about how past societies cared for infants with profound congenital differences.

In some ancient Andean societies, people with disabilities took on special roles, including religious ones. Fehren-Schmitz said a single case cannot show whether that held for Nasca society as a whole. The burial does reflect the community the infant belonged to, he said, even if only briefly.

Why it matters

Trisomy 13 and cyclopia are documented in historic and modern anatomical collections, but physical remains of this kind are rare in the archaeological record. Pairing the skeleton with genome sequencing let the researchers confirm the diagnosis rather than infer it from the bones alone, and the burial gives a rare look at how one community treated a baby with a lethal condition. The study describes one individual, so it offers no basis for general conclusions about Nasca attitudes.

Source: Live Science