A Neanderthal child may have lived at until least six years old with Down syndrome, according to an analysis of an ancient bone fragment.
Researchers from Spain suggest their findings, published in the journal Science Advances, show Neanderthals would have provided community care for the child, even if it meant sharing resources and helping raise them.
Study lead author Mercedes Conde Valverde, an anthropologist at University of Alcalá, said scientists have known for decades that Neanderthals cared for vulnerable members of their community.
But the new research provided evidence for altruistic care.
"All known cases of care [in Neanderthals before now] involved adult individuals, leading some scientists to believe that this behaviour was not genuine altruism, but merely an exchange of assistance between equals," she said.
The tiny piece of bone, smaller than a thumb, was discovered in 1989 from a site called Cova Negra in present-day Valencia in Spain.
The site was inhabited, on and off, by Neanderthals — a species of human that died out around 40,000 years ago — for hundreds of thousands of years.
Close inspection of the bone revealed it to be part of a child's skull, which encased structures that formed the inner ear.
But did it belong to our species, Homo sapiens, or was it a Neanderthal, Homo neanderthalensis?
Luckily, a number of inner ear features differ between the two.
When the researchers took hundreds of X-rays through the bone and created 3D virtual model of the child's inner ear, they found a 94 per cent chance that the fragment was Neanderthal in origin.
They also found one of the canals in the inner ear was much larger than normal, and later discovered anatomical features in the ear that could have caused hearing loss, balance problems and vertigo.
"The series of pathologies present in the individual's inner ear are only known collectively in people with Down syndrome," Dr Conde Valverde said.
"The discovery of this individual, who we nicknamed 'Tina', demonstrates the diversity [of disability] observed in modern humans was already present in prehistoric times."
'True altruism among Neanderthals'
People with Down syndrome have increased chances of developing heart and gut problems, as well as respiratory infections, and hearing and vision loss.
While a person with Down syndrome today can live close to a typical life span, this is a recent development.
Even in the early 1900s a child with Down syndrome would live, on average, nine years.
Tina lived between 273,000 and 146,000 years ago, based on other Neanderthal fossils found at the Cova Negra site.
For the child to survive at least six years would have required an immense amount of care from many individuals.
"Because of the demanding lifestyle of Neanderthals, including high levels of mobility, it is difficult to think that the mother of the individual would have been able to provide such care alone and also carry out normal daily activities," the researchers wrote.
"It is likely, therefore, that the mother required the continuous help of other members of the social group, either for assistance in performing other daily tasks (or to relieve her from performing them) or to directly assist in providing the necessary care for the child, or both."
This is not the first case of Neanderthal care.
Bones of an adult Neanderthal found in the Shanidar Cave in northern Iraq showed debilitating injuries, however the individual lived into middle age.
However, researchers have speculated that Shanidar 1's situation could have been a type of "quid pro quo", where they may have performed some kind of community act in return for care. The child in the new study, on the other hand, presumably had less ability to "give back" in that same way.
"What was not known until now was a case of an individual who had received extra-maternal care from birth, even though it could not reciprocate," Dr Conde Valverde said.
"The discovery of the Cova Negra fossil supports the existence of true altruism among Neanderthals."
A more definite diagnosis
Justyna Miszkiewicz, a biological anthropologist at the University of Queensland and Naturalis Biodiversity Center who wasn't involved in the study, said the finding was impressive, but more evidence was needed to confirm that the bone fragment definitely came from someone with Down syndrome.
"We're talking about a Neanderthal child, so that's really rare and very exciting," she said.
"But when you look closer at what they did in the paper, it becomes clear that the paper is a bit more speculative than conclusive.
"They have very limited evidence, literally one tiny piece of bone from like the skull ... but they did all the right [analytical] things."
With only the single bone fragment, the team was not able to sequence the child's DNA to confirm their Down syndrome diagnosis, despite the condition being easily picked up in genetic testing.
To have a big enough bone sample for DNA analysis, Dr Miszkiewicz said, "they would probably have to damage the entire sample. I suspect curatorial permissions probably didn't allow for it."
Adam Rohrlach of the University of Adelaide, who also researches human history via ancient DNA for Germany's Max Planck Institute, agreed the study was "exciting" but noted it could not support a diagnosis of Down syndrome.
He was part of a research team last year which identified cases of Down syndrome and Edwards syndrome in prehistoric DNA.
"We diagnosed the individuals in our study genetically, but only described the physical and osteological findings in context," he said.
"This is because Down syndrome manifests so differently in different (modern) humans, that no single skeletal marker could confidently diagnose Down syndrome."
The researchers agree that definitive proof would require DNA analysis, but this "had not yet been possible", Dr Conde Valverde said.
If correct, however, the study provides even more evidence that Neanderthals were not dim-witted or brutish.
"The idea that they're brutes has been debunked for quite a while now," Dr Miszkiewicz said.
"Clearly, there's more happening in that community. There's compassion, there's social complexity, there's other social support."
Michelle Langley, an associate professor at the Australian Research Centre for Human Evolution and director of the Griffith Experimental Archaeology Research Lab, agreed.
"You don't often get to learn much about them and it's good to remember that these were real people that lived and had lives," Dr Langley said.
"This child would have obviously had grandmothers and fathers and grandfathers and aunties and uncles that loved them very much."
