Nobody really knows why our blood is red.
That is a silly statement. Obviously since Swammerdam and van Leeuwenhoek we know that it is red, that red is the reflected spectrum of visible light on the surface structure of the red blood cell or erythrocyte. (Same reason, by the way, why our veins look blue…deoxygenated blood is dark red, oxygenated bright red, neither is ever blue.)
Red blood Cells make up around 40-50% ofhuman blood.
We also know that hemoglobin is the key protein needed for the red blood cell’s oxygen transport. Oxygen can’t bind to the water in the blood, but that oxygen binds to the transport protein: hemoglobin. (Well, some goes in plasma…but I’m trying to make a point about hemoglobin and human politics, so just bear with me.) I won’t bore you with the molecular structure, but I think it is pretty.
The cycle is simple and beautiful. As the waste carbon dioxide reacts with the water in warmer, metabolically active body tissue, the resulting hydrogen ions lower the pH value. When the pH around the hemoglobin drops, it releases oxygen.
The hemoglobin then binds most of the carbon dioxide (CO2 is more easily soluble in water and is also transported in the plasma). The heart pumps the red blood cells back to the lungs, where the pH is higher, and it releases the carbon dioxide and binds oxygen–the Bohr Effect.
So much for science. This doesn’t seem to be very political now, does it? Just hold on one moment.
In our evolutionary history, this wonderful mechanism is related to another famous mechanism in nature, one that in many ways makes our blood possible in the first place: oxygenic photosynthesis.
In this particular photosynthesis, most plants combine carbon dioxide from the air and water with electrons from sunlight to create carbohydrates and oxygen. Here is the pigment chlorophyll…not nearly as pretty, I think…but I’m not a plant:
Chlorophyll (there are several kinds) binds a photon from light. That means the energy from the light excites an electron in the molecule structure. Usually, such an excited electron would simply return to its base state and the energy would end up producing heat. However, the chlorophyll loses this electron to a receptor, passes it through a chain of reactions, and regains it through photolysis from water, creating O2.
Hemoglobin contains the cofactor heme (surprise, surprise), a chemical compound of a ferrous ion inside an organic ring called a porphyrin. Chlorophyll is also a type of porhyrin, but instead of iron, it has magnesia at its core. (For a more detailed comparison and discussion of the implications for research in molecular evolution, see: Ross Hardison’s “The Evolution of Hemoglobin Studies of a very ancient protein suggest that changes in gene regulation are an important part of the evolutionary story.” American Scientist 87.2 (1999): 126.)
Why am I telling you all this?
Bruno Latour’s recent discussion of an Anthropocene approach pointed out that to view the earth before human intervention as radically different from that after is opposed to the political epistemology of Holocene which sees one unbroken timeline of the earth and can thus buttress the nature/human dichotomy that roots in the distinction between the science of facts and the politics of values.
Does our possible, even hypothetical relation with plants–which humans perhaps respect least among the forms of life on this planet–not present a powerful reminder that nothing in us, not one piece of our bodies, has ever been separate from anything on the planet? That we are profoundly earth-bound? And can we not regain a fundamental comfort with cultural and political expressions that especially the industrialized West has grown uncomfortable with?
Colonial and imperial exploitation took the form of politics, but is also took the form of willful, violent breaks with that comfort. The colonizer’s civilization dominated the indigenous, for that was the justification of the entire project. While cooperation and cross-fertilization certainly occurred, the politics of colonialism were not interested in, even radically opposed to the consideration of the anthropocene narratives that indigenous peoples possessed and often offered as a means for orientation.
If we are serious about undoing the violence that has ruled the world for centuries, may we not think of ourselves as indeed bound with the earth, as relatives, as children of this earth, who are in evolutionary ways bound to the planet? And if we accept this proposal, must we not recognize that if we speak of “blood and soil,” of “the blood of Christ,” or of “the blood of a people,” we are always implying that the nation, the faith, the folk are also children of the earth? Of the soil?
If we understand or at least calmly reflect on the science of blood in relation to our existence as part of, not in separation from this planet, then is it not clear that we are the same stuff, and that convenience is just the creation of discomfort at the expense of other parts of the system?
In the end, nobody really knows why our blood is red, that is, why some organisms evolved to form metallo-centric porphyrins that interacted with the at that point probably new planetary atmosphere, while others did not.
But should we not try to remember remember that our blood in some way, in a distant history that is nevertheless ours, might also be green?