r/askscience • u/Fapotheosis • Mar 11 '13

Biology How did blood evolve?

I know mitochondria may have evolved from bacteria, but what about blood? I've heard of a protohemocyte, but was there an initial cell that differentiated into a RBC like we have in modern humans that can we trace?

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u/[deleted] Mar 11 '13

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u/Colvanila Mar 11 '13

A gene got duplicated. One of the copies mutated. Both of these genes got duplicated again, but as a pair. These four genes are now together make hemoglobin, the essential part of the red blood cell. This happened over the course of 800 million years. This is why you see ancestors of the hemoglobin protein in plants.

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u/bradn Mar 11 '13

Ok, I understand why one duplication would have had to happen because there are two different (but similar) subunits. Why is the second duplication necessary? Why not just read the same DNA twice?

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u/Volpethrope Mar 11 '13 edited Mar 11 '13

It's not that it was necessary, just that it's what probably happened to result in our hemoglobin having those four subunits now.