New study says humans killed Neanderthals by having sex with them. A rare blood disorder discovered in Neanderthal babies was likely the result of breeding with humans, according to a new study. […] This disorder would have made it difficult for the affected generations to reproduce — cutting their bloodline short. (The Hill, July 28, 2021) The paper: Blood groups of Neandertals and Denisova decrypted, PLoS ONE
The blood disorder is hemolytic disease of the fetus and newborn (aka HDN, HDFN, or erythroblastosis foetalis), the result of incompatible blood types (Rh incompatibility, ABO incompatibility) between gestational carrier and fetus. The Rh factor is a protein on the covering of the red blood cells. Rh factor protein on the cells = an Rh positive person; absence of Rh factor protein = the person is Rh negative. Understanding Rh Status in Pregnancy video w/traditional gender terminology. An Rh-negative gestational carrier with an Rh-positive pregnancy partner is a known risk for an HDN-affected fetus, as are certain sensitizing events which trigger antibody production.
While it was long thought that Neanderthals were all type O — just as chimpanzees are all type A and gorillas all type B — the researchers demonstrated that these ancient hominins already displayed the full range of ABO variability observed in modern humans. (ScienceDaily, July 30, 2021)
Ideally, modern prenatal screening identifies Rh-negative status early in pregnancy, and treatment with Rh immunoglobulin can prevent reaction to the fetus’s Rh-positive red blood cells — unless the gestational carrier has been pregnant before, and has already started making Rh antibodies. (Health problems usually do not occur during an Rh-negative expectant person’s first pregnancy with an Rh-positive fetus.) Possible [mild to severe, including fetal and infant death] complications; newborn treatments are dependent on the extent of the disease.
Paper excerpt: We show that Neanderthal and Denisova were polymorphic for ABO and shared blood group alleles recurrent in modern Sub-Saharan populations. Furthermore, we found ABO-related alleles currently preventing from viral gut infection and Neanderthal RHD and RHCE alleles nowadays associated with a high risk of hemolytic disease of the fetus and newborn. Such a common blood group pattern across time and space is coherent with a Neanderthal population of low genetic diversity exposed to low reproductive success and with their inevitable demise. -Condemi S, Mazières S, Faux P, Costedoat C, Ruiz-Linares A, Bailly P, et al. (2021) Blood groups of Neandertals and Denisova decrypted. PLoS ONE 16(7): e0254175. https://doi.org/10.1371/journal.pone.0254175
More on HDFN: Pegoraro V, Urbinati D, Visser GHA, Di Renzo GC, Zipursky A, Stotler BA, et al. (2020) Hemolytic disease of the fetus and newborn due to Rh(D) incompatibility: A preventable disease that still produces significant morbidity and mortality in children. PLoS ONE 15(7): e0235807. https://doi.org/10.1371/journal.pone.0235807
A few Neandertal-related previouslies on MetaFilter.