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I am developing a form of humanoid very closely related to humanity, and I am trying to see both what differences are possible, and what the explanation for various features are possible.

For example, is there a reason behind humans develop a pale blue skin tone, somewhat like Argyria, particularly Paul Karason, but a somewhat lighter and paler tone. I know it comes about due to silver poisoning, but is there any way it can develop naturally for a humanoid? It appears possible due to the Blue Fugates, but I am wondering if its theoretically feasible for this to spread out more across a species. For an example somewhat like how some monkeys have blue skin, but do not have severe disorders which effect oxygen levels like Argyria or Methemoglobinemia.

Also, what would the reasoning for a development of white/silver hair along with this?

Notes, they are a people that typically inhabited the mountains, which would allow greater isolation and divergence, and would also, from my study into the genetics and biology of the Tibetan Peoples, and they have higher nitric oxide to deal with lower oxygen levels.

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    $\begingroup$ I have fixed it, I apologize. $\endgroup$ – Zoey Apr 25 at 20:41
  • $\begingroup$ Thanks +1 on the Q. $\endgroup$ – JBH Apr 25 at 20:51
  • $\begingroup$ Related: worldbuilding.stackexchange.com/questions/65480/… $\endgroup$ – Willk Apr 25 at 20:58
  • $\begingroup$ Thank you for the link $\endgroup$ – Zoey Apr 25 at 21:47
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Congenital methemoglobinemia could be protective against red cell parasites.

The red cell is a less hospitable place in persons with congenital methemoglobinemia.

https://ashpublications.org/hematology/article/2005/1/19/19272/Red-Cell-Enzymes

Homozygotes or compound heterozygotes have methemoglobin concentrations of 10% to 35% and appear cyanotic but are usually asymptomatic even with levels up to 40%. Life expectancy is not shortened, and pregnancies occur normally. Significant compensatory elevation of hemoglobin concentration (polycythemia) is sometimes observed. The b5R activity of the erythrocytes of heterozygotes is approximately 50% of normal...

Hemglobin mutations that also decrease intracellular oxygen tension are protective against malaria (where parasites live inside the red cells) and so these mutations exist in large populations where malaria is prevalent; examples include sickle cell disease and thalassemia.

It is not outrageous to posit that decreased intra-erythrocyte oxygen tension from methemoglobinemia might also protect against similar parasites. It is interesting that this mutation is

endemic in some populations such as the Athabascan Indians, Navajo Indians, and Yakutsk natives of Siberia.

Could there be an erythrocyte-dwelling parasite in the areas where these people live? Perhaps the mutation spread because it conferred protection against the parasite and greater genetic fitness - the same as sickle cell did in Africa.

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  • $\begingroup$ Would there be a way for this to go about without the various deficits that come with it in terms of oxygenation of cells? Or to make it so they would be able to live normally despite said oxygen deficits? also, how would this go from being a disorder and start becoming a more basic part of the species as a whole? $\endgroup$ – Zoey Apr 26 at 1:46
  • $\begingroup$ Also, "Signs and symptoms of methemoglobinemia (methemoglobin level above 10%) include shortness of breath, cyanosis, mental status changes (~50%), headache, fatigue, exercise intolerance, dizziness, and loss of consciousness.[citation needed] People with severe methemoglobinemia (methemoglobin level above 50%) may exhibit seizures, coma, and death (level above 70%).[4] Healthy people may not have many symptoms with methemoglobin levels below 15%. However, patients with co-morbidities such as anemia- $\endgroup$ – Zoey Apr 26 at 1:49
  • $\begingroup$ cardiovascular disease, lung disease, sepsis, or presence of other abnormal hemoglobin species (e.g. carboxyhemoglobin, sulfhemoglobin or sickle hemoglobin) may experience moderate to severe symptoms at much lower levels (as low as 5–8%)." How would this be avoided? $\endgroup$ – Zoey Apr 26 at 1:49
  • $\begingroup$ I put in that quote from the text because it sounds like the blue people do pretty well. Clearly they can live to reproductive age and have children. Congenital methemoglobinemia is grouped with hemoglobinopathies like thalassemia and sickle cell that presumably were evolutionarily advantageous in some areas.. It is not a stretch to think methemoglobinemia could be similarly adaptive. $\endgroup$ – Willk Apr 26 at 1:57
  • $\begingroup$ Yeah, that kinda went through one ear and out the other, well, I read it so not exactly that, but regardless. Yes, reading through that again, that seems plausible. More likely Sickle Cell than Thalassemia, as Thalassemia as significant effects on skeletal structure of the face, to an extent that wouldn't fully be fitting with my conception of the species. $\endgroup$ – Zoey Apr 26 at 2:04

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