Is the eukaryotic cell a colony?

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

Sorry it's been so long without a reply - haven't been around a computer much over Christmas.I forget exactly what Dawkins wrote, and I don't have the book here to check, but he didn't discuss the matter in any detail at all. He basically just wrote that eukaryotes were formed by bacteria living together in colonies. I think my ire was raised a bit just by the way he'd declared as brute fact what I understood to still be controversial and debated.What little I know of cell biology I learnt from reading Christian De Duve, who seems to be of the opinion that endosymbiosis cannot explain most of the features of eukaryotes. His preferred hypothesis was that eukaryotes predate endosymbiosis, with much of their features being explained simply as corollaries of increasing size, with the nucleus just evolving as the bacteria's DNA is caught in an infold in the cell's membrane (which sort of thing creates the whole internal membrance system). I'd have to go and read it all again to remember more details.The idea of an already huge (by bacterial standards) cell engulfing mitochondria and the like and them surviving inside their host to gradually become a part of it made more sense to my untrained eye than the idea that huge cells arose through successive little cells joining together. I'll admit that my knowledge is limited on what's actually being proposed though - I'll try reading that Margulis article.I suppose what I was basically trying to find out was how controversial are hypotheses like de Duve's. CLearly I have a lot more reading to do on this.

Thanks for this, but do you know anywhere the article is available public access?

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