In the 14 years since it was found in an abandoned mining town in Chile’s Atacama Desert, the 6-inch skeleton has inspired fervid speculation, including theories of unearthly origins.
It had 10 pairs of ribs — two fewer than the normal human complement — and an elongated skull with a pronounced point. Despite its diminutive size, the proportion of its limbs and torso suggested this was a human. Was this a stillborn baby? A nonhuman primate? An alien being?
Now, genetic science has given these mummified remains a species (Homo sapiens), a gender (female), an age (she probably died shortly after birth) and as many as 52 genetic clues to her extreme physical abnormalities.
It narrowed her ancestry to a mix of peoples typical of those who settled the remote corner of Chile in which her remains were lovingly tucked into a pouch. Her genes suggest her ancestry was largely European and, to a lesser extent, East Asian.
The mummified skeleton has been called “Ata,” and, starting roughly four years ago, researchers from Stanford University and the University of California, San Francisco isolated and purified its DNA from marrow inside its tiny, preserved bones. Then they put a new generation of genetic sequencing technology to work.
Some of the genetic mutations they found have not been recorded before — not so surprising in a field in which the function of most genes, and of whole genetic regions, remains a mystery. Some mutations were probably carried and bequeathed by one parent only. Others appear to have been contributed by both. Still other mutations may have arisen spontaneously.
But among the mutations they found were a half-dozen or more abnormalities in genes associated with conditions such as dwarfism, scoliosis and musculoskeletal abnormalities. During fetal development, and possibly in the few days she lived, those appear to have caused her bones to fuse and age at an unusual pace.
By the time she died, the infant’s bones and the ways in which they had fused gave her the skeletal structure of a child between 6 and 8 years old.
The number of mutations affecting bone structure and growth was “well beyond what you’d expect by chance,” said Stanford researcher Garry Nolan.
The authors of the study, published in the journal Genome Research, speculated that nitrate mining may have exposed her pregnant mother to an environmental toxin.
But it may as easily have been a chance event. When it came to genetic mutations affecting the structure and growth of bones, said Nolan, the child won a sort of grim lottery, “which unfortunately was a death sentence.”