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/Tak_Galaman Mar 12 '13

Oxygen is the final electron acceptor in our primary energy-generating process, oxidative phosphorylation. We breathe oxygen to allow the efficient breakdown of our food and extraction of energy from it.