Monday, July 09, 2018

Natural selection led to racial differences in susceptibility to disease, Part II

In Part I, I introduced the idea that blacks and whites differ in how their immune systems react to pathogens, and this is due, in part, to evolution having affected relevant genes.

Here in Part II, I lay out the research evidence summarized in this study. Compared to whites, the immune systems of blacks have a stronger gene response to immune stimulation, especially the genes related to the activation of inflammatory responses. Blacks often have higher frequencies of alleles (i.e., one variety of a gene) associated with stronger proinflammatory responses to infection.

Two studies illustrate this. One tested how macrophages (i.e., a type of large white blood cell) responded to two different types of infections, and the other on monocyte (i.e., another large white blood cell) response to several pathogens such as the human seasonal influenza A virus. On average, 21% of the relevant genes appeared to show different expression between whites and blacks, and 16% of the genes reacting to immune stimulation showed that blacks had a more intense response.

Differences in genes that regulate other genes explain much of the racial difference in immune response. One variant is found in 67% of whites but only 4% of blacks. The authors found that this one difference explained from 27 to 91% of the black-white difference in immune response to various infections.

While the authors write that we have not studied very much the extent to which positive selection has contributed to racial differences in immune response, they cite at least seven studies that report signs that evolutionary pressures have caused the racial differences. Some of the relevant diseases include malaria, African trypanosomiasis (sleeping sickness), celiac disease, lupus, rheumatoid arthritis, ulcerative colitis, and systemic sclerosis.

The researchers suggest the possibility that there is an "evolutionary conflict between mounting a strong inflammatory response to effectively fight pathogens and avoiding the detrimental consequences of acute and chronic inflammation, which can lead to tissue damage and the development of autoinflammatory and autoimmune diseases."

We have recently learned that 2% of the ancestry of humans outside of Africa is Neanderthal. This may help explain the black-white differences in immune response. Higher levels of Neanderthal admixture can be detected in immune system genes in Europeans and Asians. Regulatory gene variants from Neanderthals have been found to affect the immune responses of Europeans, especially the responses to viruses.

All these racial differences in genes and immune systems are really weird since "race experts" tell us that this race stuff is just an hallucination dreamed up by evil white people.


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