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Chapter 60 : Begetting the Eukarya: An Unexpected Light
Concerning the origin of eukaryotic cells, much has been written but almost everything remains to be settled. No one disputes that mitochondria derive from free-living bacteria that established an intimate symbiotic relationship with a host of some kind and progressively turned into organelles, workhorses of metabolism, and a hallmark of eukaryotic organization. But consensus ends here; the nature of that host, the timing and circumstances of the partnership, and its role in generating the conspicuous complexity of eukaryotic cells all remain elusive and entangled in controversy. In a comprehensive review of the subject published in 2006, Martin Embley and William Martin (6) concluded bleakly that: “the evolutionary gap between prokaryotes and eukaryotes is now deeper, and the nature of the host that acquired the mitochondrion more obscure, than ever before.” No one will claim that the darkness has been lifted, but just in the past few years this intractable subject has begun to appear in a fresh light.