Convoluted human evolution: Denisovan immunity contribution (Introduction)

by David Turell , Wednesday, January 18, 2023, 18:20 (465 days ago) @ David Turell

To Pacific islanders:

https://www.science.org/content/article/mysterious-ancient-humans-may-have-given-people...

"Researchers have known for a decade that living people in Papua New Guinea and other parts of Melanesia, a subregion of the southwest Pacific Ocean, inherited up to 5% of their DNA from Denisovans, ancient humans closely related to Neanderthals who arrived in Asia about 200,000 years ago. Scientists assume those variants benefited people in the past—perhaps by helping the modern humans better ward off local diseases—but they have wondered how that DNA might still be altering how people look, act, and feel today. It’s been difficult to detect the function of Neanderthal and Denisovan DNA in Melanesians, however, because scientists have analyzed so little genetic data from living humans in Papua New Guinea and other parts of Melanesia.

"The new study overcomes that problem by using genetic data from 56 individuals from Papua New Guinea that were recently analyzed for another paper, part of the Indonesian Genome Diversity Project. The researchers, mostly from Australia and New Guinea, compared those genomes with those of Denisovans from Denisova Cave in Siberia, as well as Neanderthals. They found the Papuans had inherited unusually high frequencies of 82,000 genetic variants known as single nucleotide polymorphisms, which arise from differences of a single base or letter in the genetic code—from Denisovans.

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"In Papuans, the scientists found many Denisovan variants that were located near genes known to impact human immune responses to viruses and other pathogens, such as the flu and chikungunya. Next, they tested the function of eight Denisovan gene variants associated with the expression of proteins produced by two genes in particular, OAS2 and OAS3, “lymphoblastoid”—cell lines of B cells, a type of white blood cell that makes antibodies critical to the body’s immune response. Those cell lines were collected from Papuans by study co-author Christopher Kinipi, a Papuan physician and health services director at the University of Papua New Guinea.

"Two of the Denisovan genetic variants found in those Papuan cell lines lowered the transcription or production of proteins that regulate cytokines, part of the immune system’s defense against infections, reducing inflammation. This subdued inflammatory response could have helped Papuans weather a rash of new infections they would have encountered in the region.

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"These findings dovetail with earlier work on the role of Neanderthal variants in living Europeans. Studies of both Neanderthal and Denisovan DNA in different populations are showing how mating with archaic humans—long-adapted to their regions—provided a rapid way for incoming modern humans to pick up beneficial genes, says computational biologist Janet Kelso of the Max Planck Institute for Evolutionary Anthropology. The study shows this sort of gene swap was “an important mechanism for how humans adapted quickly [to new challenges], specifically pathogens,” says human geneticist Luis Barreiro of the University of Chicago."

Comment: dhw has asked why so many pre-sapiens were evolved. Helping with immunity indicates one good reason. This fits my theory of a God who does not have, or need, full control over all circumstances. Rather than specifically infecting groups of people, letting them become infected at random still results in good immunity levels, especially if effective genes can be passed around in advance.