Any Cougars enthusiast or BYU student will tell you that true BYU fans bleed blue (I’m sure bleeding team colors is actually common for any hardcore fan base, but let’s pretend it exclusive to BYU). Every time I hear this statement, I think about Spock. True his blood is more green than blue, but the point is that it isn’t the usual red that we are all used to seeing. Almost all vertebrates bleed red (AKA use hemoglobin to transport oxygen). So that brings me to a recurring question I have: What would it take for a human to have blood of a different color?
Blood in any other color besides red is actually a common trope in science fiction, eliciting immediate images of all things foreign and alien. It is not that hard to imagine alien life developing and evolving in a completely different environment. I am not a chemist, and do not claim to understand the different blood pigments and their advantages. This has left me at a disadvantage when trying to understand peer-reviewed articles on the subject. But, I have found some interesting sites that talked about different pigments in a way that I could understand.
This site: http://www.compoundchem.com/2014/10/28/coloursofblood/ explains the different blood pigments found in living things on Earth. It does not include hypothetical and synthetic blood pigments that have been created in laboratories.
Since Hemocyanin is the second most common pigment on Earth, I decided to look closer at it. There is a lot of information out there, but I won’t take up my whole post describe it. Instead, here is a quote I found interesting from one of the sites:
“The copper-containing pigment hemocyanin, second in breadth of distribution only to hemoglobin, is found in the blood of various mollusks and arthropods. Unlike human blood, which is bright red in the arteries (oxygenated) and dark red in the veins (deoxygenated), hemocyanin blood is a beautiful blue in the arteries and crystal—clear colorless like water in the veins. Hemocyanin is always found floating freely in the blood plasma, rather than being trapped inside corpuscles as are the relatively smaller molecules of Hb. This copper-based, proteinous, non-porphyrin blood pigment is only about 25% as efficient an oxygen carrier as hemoglobin. Might true extraterrestrial “blue bloods” exist? On a world with very high surface pressures and abundant oxygen we might suspect that the higher efficiencies achieved by Hb might not be needed for survival. Hemoglobin might then never have evolved at all.” (http://www.xenology.info/Xeno/10.4.htm)
For the story I am writing, I specifically wondered if it was possible for human blood to develop different colored blood under the right circumstances. If a world had high enough pressure, enough oxygen, and the right metal chemistry ready available, would we see different blood chemistry evolve over time? How feasible is it, and exactly how long it would take? Would there be significant genetic changes, and would other phenotypes be affected? And is it possible to use hemoglobin AND another pigment at the same time? I am working under the assumption that given enough time and in a different enough environment, people would make use of other blood pigments.
That is the beauty of writing speculative evolution. At the end of the day it is all speculative. At first, I was afraid to write about the world I imagined because I was afraid science would prove that what I wrote couldn’t happen. Then I thought about it. Some of the best science fiction stories incorporate ideas that conventional science finds unlikely or impossible. It isn’t the prefect scientific explanations that cause people to fall in love with these stories. We love the what-if scenarios. We love to think about new worlds that test our prior knowledge and understanding of how our own world works. I decided to not let my fear of being wrong stop me from writing my fictional world.
I stopped asking myself if what I wrote was possible, and instead focused on what it would take to make it possible. So if Spock can be half-human, half-vulcan and still have Vulcan blood chemistry, then my humans can develop other blood pigments too. At least they can in my world. 🙂