When a bizarre 15cm skeleton was discovered buried in a leather pouch behind an abandoned church in the Atacama Desert of Chile in 2003, it baffled the world.
The tiny figure had a cone-shaped head, the bones of a 6-year-old and 10 pairs of ribs instead of the usual 12, leading to speculation it could be extraterrestrial.
But now, after detailed genetic analysis of the little mummy - nicknamed "Ata" - scientists have concluded that its home planet is definitely Earth, the Daily Telegraph reports.
Tests by experts at Stanford University and the University of California confirmed the skeleton is a human female baby, who suffered an array of genetic mutations and probably did not survive long after birth.
Dr Garry Nolan, professor of microbiology and immunology at the Stanford University School of Medicine, began the scientific exploration of Ata in 2012, when a friend called saying he might have found an "alien".
"I had heard about this specimen through a friend of mine, there were some extraordinary claims put forward, and I managed to get a picture of it," said Nolan.
"You can't look at this specimen and not think it's interesting. It's quite dramatic. So I told my friend, 'Look, whatever it is, if it's got DNA, I can do the analysis."
The team took DNA from bone marrow in Ata's ribs, and compared it to human and primate genomes. It showed the mummy was human, and female, with a mix of Native American and European ancestry, which is typical of that region of Chile.
The researchers next looked for genetic clues that could explain Ata's small stature, multiple bone and skull abnormalities, abnormal rib count, and premature bone age. The smallest baby ever born was recorded at 22cm, but Ata was nearly 7cm shorter.
The genomic results turned up a slew of mutations in seven genes that separately or in combinations contribute to various bone deformities, facial malformations or dwarfism.
Some of these mutations, though found in genes already known to cause disease, had never before been associated with bone growth or developmental disorders.
Nolan believes further research into Ata's speedy bone ageing could one day benefit patients.
"Maybe there's a way to accelerate bone growth in people who need it, people who have bad breaks," he said.
"The symptoms and size of this girl were extremely unusual. Nothing like this had been seen before. Certainly, nobody had looked into the genetics of it."
Dr Atul Butte, director of the Institute for Computational Health Sciences at the University of California-San Francisco, added: "What really came of this study was the idea that we shouldn't stop investigating when we find one gene that might explain a symptom.
"It could be multiple things going wrong, and it's worth getting a full explanation, especially as we head closer and closer to gene therapy.
"We could presumably one day fix some of these disorders, and we're going to want to make sure that if there's one mutation, we know that - but if there's more than one, we know that too."
Nolan said he also hopes, one day, Ata will be given a proper burial. Judging from the skeleton's intact condition, he said, it is probably no more than 40 years old.
"We now know that it's a child, and probably either a pre- or post-term birth and death," he said.
"I think it should be returned to the country of origin and buried according to the customs of the local people."
The research was published in the journal Genome Research.