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Part of this story I'm writing involves a human subspecies who are adapted to extremely high altitudes -- as high or higher than our real world's Tibetan population, let's say. I've done research that indicates that the Tibetan adaptation to high altitudes in part involves either a decreased red blood cell count or a dramatically reduced amount of hemoglobin. I'm not sure if those terms are synonymous (I'm guessing they are), but sources agree on it being related to the EPAS1 gene. Anyways, I'm thinking about using the same mechanism for this population, although since they live higher up, and they've had a longer time to adapt, I assume they would have a proportionately more intense version of the Tibetan adaptations.

What I want to know is whether a significantly reduced red blood cell count, across this population, would be visibly discernible in their blood to the unaided eye, and thus what color their blood would be relative to lowlander red blood. Would it be less vibrantly red? More so? I initially wanted blood as vibrant as red paint, but I'm trying to be realistic.

An absence of sources detailing Tibetans having differently colored blood, to me, points to them not having differently colored blood. And I suspect blood color would vary more with degree of oxygenation than it would with cell count.

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    $\begingroup$ Tibetan adaptation to high altitudes in part involves either a decreased red blood cell count or a dramatically reduced amount of hemoglobin Are you sure about that? I am pretty sure it is just the opposite (less oxygen means that more hemoglobin is needed to improve the gas exchange at the lungs); in facts elite sportists often train in high altitudes to increases red blood cell count... $\endgroup$ – SJuan76 Jun 26 '15 at 18:13
  • $\begingroup$ And yes, there is correlation between red cells and hemoglobin (red cells basically being bags fulls of hemoglobin). $\endgroup$ – SJuan76 Jun 26 '15 at 18:14
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    $\begingroup$ SJuan76: My sources: a study on NCBI and an article from Berkeley $\endgroup$ – undine_centimeter Jun 26 '15 at 18:31
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    $\begingroup$ this is more biology than worldbuilding... $\endgroup$ – ArtOfCode Jun 26 '15 at 21:27
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You won't notice a difference.

What the research is showing is that Tibetans don't have the elevated red blood cell count or hemoglobin levels expected when others (lowlanders like me) go to high elevations. Essentially, they have blood that more closely matches what lowlanders have at low elevations, but still do quite alright. As stated in this paper:

The Tibetan hemoglobin distribution closely resembled that from a comparable, sea-level sample from the United States, whereas the Aymara distribution was shifted toward 3–4 gm/dl higher values.

The Aymara don't have this gene (EGLN1) which keeps the hemoglobin levels low, but they also live at fairly high altitudes. When lowlanders go to higher elevations our red blood cell count increases and hemoglobin concentration increases. This helps us get enough oxygen, but it also causes altitude sickness, so is detrimental over long periods of time.

So, you may notice a difference at altitude, but it's the lowlanders who will have slightly different color of blood. But the difference is small.

enter image description here

Tibetan males and sea level American males are in the ~14µg/dL range (the second to rightmost block). A lowlander going to high altitude will have a blood color darker than the rightmost block, at >19µg/dL. I actually can't find a suitable image for how deep/dark the color gets, but the trend seems to indicate it will get quite dark.

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    $\begingroup$ Oh, thank you. So the high-altitude populations have the same color at high elevation as the lowlanders do at low elevation. Is it the case, however, that blood with more hemoglobin is brighter red, regardless of altitude? $\endgroup$ – undine_centimeter Jun 26 '15 at 18:40
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    $\begingroup$ More hemoglobin is actually a deeper red. I'll add a photo. $\endgroup$ – Samuel Jun 26 '15 at 18:43
  • $\begingroup$ @undine_centimeter It's advisable to hold off on accepting to encourage better answers from others. $\endgroup$ – Samuel Jun 26 '15 at 18:56
  • $\begingroup$ Right, sorry about that. Thanks for providing this information, anyway. $\endgroup$ – undine_centimeter Jun 26 '15 at 19:03

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