I was recently reading
Climbing Mount Improbable by Richard Dawkins*, and was slightly jarred by his bald-faced assertion, towards the end of the book, that eukaryotic cells evolved as colonies of prokaryotes. I'm a long way from being a microbiologist, so my views may be slightly confused, but this doesn't satisfy me at all as an explanation of the origin of eukaryotes, and so I thought I'd turn to where I knew there were plenty of people better educated than me to offer their opinions.
I accept the fact that organelles like mitochondria, chloroplasts, and possibly peroxisomes are descended from originally independent organisms, but none of these seem to me to be essential, defining features of a eukaryotic cell. It seems perfectly conceivable to me to imagine an ancient eukaryotic cell, vastly bigger than prokaryotes, with a nucleus and an internal transit system, but without any endosymbiotic organelles. On the other hand, I don't see how the idea that eukaryotes are colonies explains much about eukaryotes that isn't explained by the idea of endosymbiotic cells becoming part of a pre-existing eukaryote.
If this isn't just a whim of Dawkins that I'm getting unjustly upset about, is there anything more to support the idea of colonies of prokaryotes forming eukaryotes?
*I'd recommend everyone to borrow it from a library and read the chapters on the eye, flight and fig trees. As for the rest of it, you can find better things to do with your time.
Edited by caffeine, : linguistic style
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