It's a skeletal conundrum made up of perplexing features. It's only 6 inches tall -- but initial estimates of the age of the bones were consistent with a child aged 6 to 8 years.
The long, angular skull, slanted eye sockets and fewer than normal ribs -- 10 pairs rather than the normal 12 -- only deepened the mystery.
Questions surrounding the discovery led to speculation that it was a previously unidentified primate or even an extraterrestrial life form.
The skeleton, dubbed Ata, was featured in TV shows and a documentary, "Sirius," in which a UFO researcher attempts to figure out Ata's origins.
Now, the authors of a study based on five years of genomic analysis want to set the record straight: Ata is human, albeit one with multiple bone disease-associated mutations. And they believe that their findings, published Thursday in the journal Genome Research
, could help diagnose genetic mutation-based cases for living patients.
In 2003, Ata was found in a deserted mining town called La Noria, in Chile's Atacama region. It was thought to be ancient at first, but initial analysis conducted in 2012 proved that the skeleton was only about 40 years old. This meant DNA would still be intact and could be retrieved for study.
The widespread speculation surrounding Ata brought the case to the attention of Gary Nolan, senior author of the new study and professor of microbiology and immunology at Stanford University.
"I learned about this through a friend who was interested in the entire area of extraterrestrial life," Nolan wrote in an email. "He told me about a documentary coming out ('Sirius' ... you can find it on Netflix now) which was to feature the 'Atacama Humanoid.'
It was claimed that this was possibly the mummy of an alien.
"That was a significant claim in and of itself. More shocking though was the picture I was provided that was part of the online publicity. I decided to contact the movie directors (basically on a dare ...) to tell them it was possible to do a sequencing of the specimen (if it had earthly DNA ...) to determine its origin."
Nolan and his colleagues signed a confidentiality agreement, and the directors agreed to report Nolan's findings, even if the results indicated that Ata's DNA was human.
Nolan wanted to study Ata for several reasons. The extraordinary specimen could have been a previously unrecognized primate species, some sort of human deformity or something else entirely. Nolan said he and his colleagues never believed it could be an alien.
They wanted an answer to the basic question: "What is it?"
DNA analysis would tell the true story. A sample extracted from the bone marrow of Ata's ribs was used to conduct a whole-genome sequence analysis.
It was compared with human and primate genomes and determined to be a human female, probably a fetus, with Chilean ancestry. Although dating initially estimated the bone age of the skeleton at between 6 and 8 years, the researchers found that the remains had a rare bone-aging disorder that made them seem older than the person they belonged to.
At first, 8% of the DNA didn't match with human DNA. Resea