I realise that it does nothing to really tackle the main point of the OP, but I do think it changes the nature of the challenge slightly. If the nucleus evolved from a parasitic or symbiotic organism that had a linear chromosome (in other words never made the transition to circular) then the chain of events stops being:
Linear => Circular => Linear (which seems like a wierd way of going about things)
to
Linear => Circular and Linear
Parasitic organisms would get around the problem of chromosome stabilisation by replicating like mad and using the host to keep their genomes relatively small, whilst others developed circular chromsomes to become all-singing all-dancing biochemical factories. It removes the absolute requirement for telomeres to survive, and presents the possiblity that parts of the hosts genome could be co-opted by the parasitic DNA to stabilise the ends of the relatively unstable linear chromosome (I
think this is what Loudmouth was saying).
As for what the abstract said about the chain of events, I think I could sum it up like this:
- The virus (or similar parasite) has a mechanism to trick the host cell into engulfing it.
- The parasite then gets 'stuck' inside the host cell and a sort of symbiosis exists with a circular genome knocking around in the cytosol and a proto-nucleus.
- The mechanism for engulfing things would still be active and the ability to prey on smaller cells would reduce the need for the first eukaryotes to make a lot of nutrients themselves.
- As the genes in the circular chromosome would be less needed it would be easy to imagine a situation where important genes are sequestered by the nucleus and the rest of the 'host' geneome is lost completely.
This cell-turned-predator idea would also explain the advent of mitochondria and chloroplasts (but that
is Off-topic)
Concerning the new topic suggestion: I certainly like the idea of a thread entitled 'All men are parasites' (or similar), but I'm afraid I don't know too much about the evolution of sex so I might have to do a bit of digging or turn it into more of an enquiry type of topic - unless you want to have a shot at it of course.