In 2003, Oscar Munoz found a mummy in the Atacama Desert ghost town of La Noria. The six-inch-long mummy, now called Ata, has an elongated skull, oddly shaped eye sockets, and only ten pairs of ribs... which helped fuel wild speculation that she was an alien hybrid. Ata was sold several times—probably illegally—and ended up in the private collection of Barcelona entrepreneur and UFO enthusiast Ramón Navia-Osorio. A 2013 documentary called Sirius soon helped immortalize Ata, focusing heavily on the alien hybrid claims.

When a team led by University of California, San Francisco bioinformatics researcher Sanchita Bhattacharya recently sequenced the tiny mummy’s genome, however, it revealed only a girl of Chilean descent. There were a complicated set of genetic mutations, including some usually associated with bone and growth disorders and a few more that have never been described before. Those mutations, the researchers claim, may help explain her unusual appearance.

It’s easy to see why the team's March paper attracted so much interest: a high-profile urban legend was fully debunked at last, but now there were hints at compelling medical discoveries. Most press outlets presented the results as conclusive, cut-and-dried science—except for a few UFO fan sites that loudly insisted the study was part of a cover-up. But even beyond the extraterrestrial exchanges, things have gotten very complicated, both in terms of the scientific claims and in terms of whether the research should have been done at all.

A scientific controversy

The complaints started only three days after Bhattacharya and her colleagues, including Stanford University immunologist Garry Nolan, published their paper in Genome Research. Chilean microbiologist Cristina Dorador of the University of Antofagasta published an article on Chilean science news site Etilmercurio, criticizing the geneticists for working with samples obtained from a mummy that had probably been illegally smuggled out of Chile. By March 28, The New York Times reported that the Chilean National Monuments Council had launched an official inquiry into the provenance of the remains, and Chilean anthropologists and archaeologists criticized the ethics of the study and called for a retraction of the paper.

Nolan and co-author Atul Butte, a computational biologist at the University of California, San Francisco, published a response in the journal Genome Research on March 30, defending the ethics and scientific merits of their work. The journal also issued a statement defending their ethical standards and decision to publish. But now a group of anthropologists is challenging not only the ethics but the science behind the study.

This group, led by University of Otago bioarchaeologist Siân Halcrow, claims that Ata’s appearance was never actually that unusual—if you know what the bones of a human fetus are supposed to look like halfway through gestation. And if they’re right, it means the genetic study was unnecessary in the first place to prove Ata’s humanity or to understand the appearance of her bones.

Bones of contention

“There is nothing about Ata that suggests she is anything but a mummified human fetus,” bioarchaeologist Kristina Killgrove of the University of West Florida and the Ronin Institute told Ars. “Her body looks like a normal fetus around the mid-point of development and most likely represents a miscarriage.”

Fetal skeletons don’t look quite like fully developed infants. A fetus’ 11and 12ribs often haven’t developed by the middle of a pregnancy, for instance. And the process of passing through the birth canal tends to compress babies’ skulls into a slightly elongated, cone-like shape. Combine that with processes at work on the body after burial , the archaeologists say, and Ata’s appearance makes perfect sense.

This argument first emerged in 2013, when Nolan announced the results of an initial genetic study to Science Magazine. Stony Brook University School of Medicine anatomist William Jungers, in an interview at the time, remarked, “Genetic anomalies are not evident, probably because there aren't any.” Jungers is now part of Halcrow’s group.

What about the mutations Bhattacharya and her colleagues found in Ata’s genome? Halcrow and her colleagues say that the ones usually associated with bone and growth disorders wouldn’t impact the appearance of Ata's skeleton so early in her development. And they argue that it could just be coincidence that the previously unidentified mutations turn up at locations associated with bone formation and growth. Mutations, especially ones that affect only a single DNA base, are surprisingly common. And generally, they have no effect on a person’s body because they occur in regions of DNA that don’t actually code for anything.

Although headlines have claimed that Bhattacharya and her colleagues found the genetic mutations that explain Ata's appearance, the researchers themselves have been much more cautious. In an interview with Ars prior to the study's publication, Bhattacharya said that it would take more work in the lab, possibly using mice as a model, to figure out whether these specific mutations actually cause any deformities.