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.

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

Here's a figure from a new study that reviews research on racial differences in immune system response. Notice how the regions with the highest abundance of pathogens (disease-causing microorganisms) are the northern half of South America, central sub-Saharan Africa (SSA), and southeast Asia.

The graph also traces important moves humans have made over the past 65,000 years, and the right panel shows that people with European ancestry suffer from high rates of death from Parkinson's and Alzheimer's, while those with SSA ancestry experience a high incidence of mortality from cardiovascular disease, surgical complications, meningitis, diabetes, septicemia (blood poisoning), kidney inflammation, perinatal death, asthma, childbirth, and HIV.

In the next post, I'll summarize the evidence presented in the study that immune system genes show signs of evolutionary adaptation to the different pathogen environments that races have lived in.

A big black-white difference in a gene affecting the immune system

This new study looks at genetic differences in black and white women that affect immune system response. The top hit the researchers identified was a genotyped variant rs2814778, which is called the Duffy-null allele. 66% of black women carried the CC variant; 29% had the CT and 5% had the TT genotype. Compare this to white women: 100% of them have the TT genotype.

Now, the "experts" tell us race is not real. For example, they tell us that, say, whites differ among themselves much more than they differ from blacks. But look at this study: there is ZERO variation among whites, black women are fairly uniform too, and where they differ among themselves, it is due to having varied amounts of white ancestry.

It is widely thought that this geographic genetic diversity is the result of a strong positive selection for protection from malaria infection found in West Africa thousands of years ago. Blacks have faced different environments over tens of thousands of years, so what kind of researcher would claim that any genetic differences between blacks and other groups would be minimal or unimportant? Being able to survive malaria is pretty damn important, and the magnitude of the black-white difference in rs2814778 speaks for itself. The kind of researcher who would minimize and dismiss this is a dishonest researcher.