Researchers have sequenced the full genome of a weird, 15-centimeter-tall human skeleton and identified mutations that may be responsible for its peculiar appearance, putting an end to a long-standing mystery that previously enthralled the unidentified flying object community.
Scientists were perplexed by the specimen, discovered in the Chilean desert in 2003, because of its skeletal abnormalities and bone development that appeared far more advanced than its size suggested. However, comparing its DNA to that of another human has identified many abnormalities in genes implicated in bone ailments, confirming once and for all that this being is from our world.
The skeleton was discovered in a little leather sack in an abandoned settlement in Chile’s Atacama Desert (hence the specimen’s name, Ata), however the study’s main author, Garry Nolan, an immunologist at Stanford University in Palo Alto, California, admits that its past is “a little unclear.” Ata finally made its way to Spain, where it piqued the interest of filmmakers working on a documentary about alien life.
Nolan agreed to sequence the DNA of the specimen on the proviso that if he discovered it wasn’t an alien, the documentary would make that obvious. As Science reported at the time, Nolan discovered that Ata was undoubtedly human, but he was left wondering what produced the specimen’s unusual bone form.
One of the main puzzles was why Ata, who was only 15 cm tall and hence the size of a 5-month-old fetus, had bone development in its knee growth plates that would ordinarily be found in a 6-year-old. This fueled speculation that Ata was a child suffering from a new form of dwarfism. Others, however, felt Ata was a fetus with genetic mutations that caused its advanced bone age, as well as a slew of other abnormalities like having two sets of ribs fewer than normal and an unusually shaped head.
The researchers sequenced DNA from Ata’s bone marrow and mapped it against a human reference genome. They revealed that Ata was undoubtedly human, but she was also female and, based on the preservation of her DNA, was born within the last 500 years—though her skeleton was discovered so well-preserved that she is probably only a few decades old, according to Nolan. Ata’s DNA also suggested that she was most likely of Chilean descent; she contained traces of European and Asian heritage, implying that she is a result of recent migrations.
The examination of Ata’s DNA revealed over 3 million single nucleotide variants (SNVs), or spots in the genetic code where a “letter” differs across persons. To see if any of these could account for her problems, the researchers focused primarily on SNVs in protein-creation areas and filtered out variants that are prevalent in the general population, reducing them to only 54. Many of these mutations were previously unknown, but the researchers discovered that the majority of them happened on genes known to be involved in skeletal formation and previously implicated in bone abnormalities, as they report today in Genome Research.
They discovered SNVs in genes that encode the collagen proteins that build up bone and cartilage, as well as in areas where previous mutations have produced problems similar to Ata’s, such as fewer-than-normal ribs or short height.
According to Nolan, the investigation shows that Ata was probably certainly a preterm baby with a variety of anomalies in her DNA that could explain her odd diseases. “This species won the bad luck lottery,” he explains. “We are all born with various mutations, and that is evolution, but the mutations do not always line well.”
These conclusions are not universally accepted. Geneticist Michael Briggs of Newcastle University in Newcastle upon Tyne, U.K., who specializes in bone illnesses, believes it’s “extremely unlikely” that all of these mutations are harmful and merely happened to appear together by chance. He believes that Ata’s skeletal anomalies are more likely caused by one or two mutations, but “they haven’t gone and done any functional investigations, which you’d ordinarily do to verify that [a] variant was disease-causing.” Briggs claims that without such investigations, such as those conducted in mice models or tissue cultures, it is hard to determine which variations are to blame.
He also mentions that several of the 54 SNVs discovered in Ata have previously been identified as benign in the human population, ruling them out as potential perpetrators.
Nolan admits that the role of Ata’s mutations cannot be shown conclusively without experiments. However, he notes that genes are “team players,” and that SNVs that are harmless in isolation may cause disease when combined with other harmful variants.
That discussion may rage on, but the one regarding Ata’s extraterrestrial origins, according to William Jungers, a paleoanthropologist and anatomist at the State University of New York at Stony Brook’s School of Medicine, should come to an end. “The alien frenzy was nonsense fostered for media attention,” he claims. “This study puts that folly, as well as poor little Ata, to rest.”