Iñigo Olalde
Geneticist and Ikerbasque and Ramón y Cajal researcher at the University of the Basque Country (UPV/EHU)
It is a study that complies with all established protocols for the recovery of DNA from old samples and the minimisation of the risk of contamination with modern DNA. It is a study of excellent quality.
It is not the first time that Down's syndrome cases have been identified in ancient samples, but this work is the first large-scale search. They have analysed genomic data from 10,000 ancient individuals and, in addition, they describe a new statistical method for identifying cases of trisomies that is adapted to the special characteristics of ancient DNA, which is often highly degraded. Future studies of ancient DNA will most likely use this new method to search for trisomy cases.
On the technical side, I don't see any major limitations. Perhaps in the interpretation, when they state that these individuals with trisomies were identified as full members of these communities, it should be said that it is possible that they were not aware that these individuals (all newborns) had any pathology and that is why they were given the standard burial ritual. In the case of Down's syndrome, for example, at the moment of birth, traits that we now know are associated with Down's syndrome can be seen, but it is possible that ancient societies were not aware of this association. This limitation is mentioned in the article.