Svante Pääbo and collaborators reconstructed the genome of the Denisova hominins and announced that they were a new species, that they interbred with our species, and that the DNA results suggest that they had dark hair, eyes, and skin. From the abstract: "It represents a hitherto unknown type of hominin mtDNA that shares a common ancestor with anatomically modern human and Neanderthal mtDNAs about 1.0 million years ago. This indicates that it derives from a hominin migration out of Africa distinct from that of the ancestors of Neanderthals and of modern humans. The stratigraphy of the cave where the bone was found suggests that the Denisova hominin lived close in time and space with Neanderthals as well as with modern humans." With Q Fu, J. M. Good, B. Viola, MV Shunkov, and A. P. Derevianko.

First complete sequence of a Neanderthal genome. With more than 20 co-authors.

Paleogenomic study of a single bone fragment from a female hominin found in the Denisova Cave in the Altai mountains of Russia provided "direct evidence for genetic mixture between Neanderthals and Denisovans on at least two occasions: once between her Neanderthal mother and her Denisovan father and at least once in the ancestry of her Denisovan father.”

The authors indicated that finding a 1st generation Neanderthal Denisovan offspring among the small number of archaic specimens sequenced to date suggests that mixing between late Pleistocene hominin groups was common when they met.

Order of authorship in the original publication: Slon, Mafessoni, Vernot...Pääbo. Available from PubMedCentral at this link.

(Thanks to Juan Weiss for this reference and its interpretation.)

Expanding on previous findings by a genome wide association study of severe COVID-19, specifically with respiratory failure which had found that a gene cluster residing on chromosome 3 had a significant association with severe acute respiratory failure post infection, the authors showed that:
1) Chromosome 3 in those patients is specifically populated by a 50,000 DNA nucleotides long segment that entered the human population by gene flow from Neanderthals or Denisovans.
2) This long haplotype entered the Neanderthal population, and was transmitted by Neanderthals to present day humans about 40,000-60,000 years ago.
3) This specific genomic segment is carried by about 50% of people in South Asia, is almost absent in East Asia and is carried by about 16% of European humans overall.
4) The authors posited that this genomic cluster was maintained in the genome most likely as the result of positive natural selection in Neanderthals because it probably contributed to the species chances of survival and reproductive success.

Order of authorship in the original publication: Zeberg, Pääbo. Available from nature.com at this link.

(Thanks to Juan Weiss for this reference and its interpretation.)