Nic Tamzek

PS: I should add that while Margulis & co write a lot about early evolution, she comes in for a lot of (IMO deserved) bashing from e.g. Cavalier-Smith, who IMO is a lot more careful about things instead of wildly flinging assertions in every direction.

I don't mean to start a fight, she was obviously proved everyone wrong about endosymbiosis...but she is still clinging to the obviously wrong cilium-from-a-spirochete hypothesis which Cavalier-Smith has beat up repeatedly since the early eighties.

Oolon Colluphid

Ref Margulis’s symbiotic bacteria, in my usual simplistic way the argument has been settled as far as I’m concerned by the finding that the mitochondrial genome is so similar to that of Rickettsia prowazekii bacteria. We’re happy enough to conclude for animals that if genomes are similar, then they’re owners are related, so it looks pretty ‘case closed’ (refinements notwithstanding ) for mitochondria. I gather -- don’t recall where from -- that similar work has been done for chloroplasts.

More details at:
http://www.nature.com/genomics/papers/r_prowazekii.html

As for Maynard Smith and Szathmary, a simpler version of the book Nic mentioned is their The Origins of Life.

Cheers, DT

Quetzal

And let us not forget Dr. Margulis' most recent broadside against the evils of competitive selection and the neo-Darwinian synthesis: Acquiring Genomes. As in much of her previous writing, she starts with what is known (or can be reasonably inferred) from her SET, and launches it into orbit. She successively attacks random mutation as the source of population variation, natural selection as the creative force in evolution, insists that all speciation events are based on symbiosis (rather than the mundane allopatry etc), slams "dogmatic Darwinism", and drags in her (and Lovelock's) metaphysical Gaia Hypothesis to tie everything together. (Having said that, the book is worth reading - she discusses some GREAT examples of symbiosis in higher organisms). Unfortunately, as always she simply can't content herself with a mundane extrapolation from current information - no, it has to be pan-galactic extrapolation, and widespread use of rhetorical license to boot. Still, worth reading.

Naturally, the creationists lost no time in seizing on the book as yet another "evolutionist who denies evolution". The book hit the shelves (at least in DC) toward the end of July, and the first Impact article appeared in September, proclaiming Acquiring Genomes as the death knell of evolution.

And I agree: Szathmary/Maynard-Smith's book Transitions is awesome.

lpetrich

Chloroplasts are clearly descended from cyanobacteria, though which cyanobacteria are closest to chloroplasts is still unclear, and it is unclear how often the cyanobacterium endosymbiosis happened.

However, it is likely that the "primary" endosymbiosis had happened only once, but there is some controversy over how many "secondary" endosymbiosis events there have been. Such events are a photosynthetic protist becoming a "chloroplast" of another protist, something which has happened several times.

And a curious twist of evolution is that a chloroplast can lose its photosynthetic function and become vestigial. That has happened to Plasmodium, the malaria bug, which has "apicoplasts" that continue to exist on account of the biosynthesis that they perform. This curious circumstance has provoked the exploration of herbicides as malaria medicines.

Roller

Hello!

Thank you all for your replies!
This is very interesting. Gotta catch up on those books that I got

(edit: spelling errors)

DNAunion

DNAunion: Define "define".

Dr.GH

We have a new president and a new "pairadimes"

"What duh yu mean 'define?' I can bomb the shit out of ya. Huh!"

Doubting Didymus

Are you going to answer the question or act like a child? We've done a few interesting things in RNA experiments, and I wanted to know what you meant by 'synthesised from scratch'. What start conditions do you find acceptable? Amino acids? A primordial soup simulation? water? a big black top hat? What kind of RNA would impress you? Self replicating? Capable of carrying out metabolic functions? or just plain old existing?

Stop being so damn suspicious of everything. I am not trying to argue semantics with you, or challenge and belittle you. Sometimes when people ask a question, it really is just because they want to know the answer.

DNAunion

DNAunion: Tsk tsk. You guys are so quick with the insults: a sure sign of an inferior mind :-)

You asked me an ambigious question and I asked for clarification. You could have been asking for:

1) A simple and non-techincal statement that sums up what I basically meant.

2) A working definition.

3) An accurate definition such as "an irrational number is a number whose decimal representation neither terminates nor repeats".

4) An accurate and "strong" definition such as "an irrational number is a number that cannot be written as a ratio of two integers" (you know, a Principia-type definition).

I wanted to know what you meant.

DNAunion

DNAunion: An example would be starting with simple gasses (methane, ammonia, etc.) and forming the three individual parts of ribonucleotides (ribose, phosphate groups, and the four nitrogenous bases), then hooking them together correctly to actually form ribonucleotides, then having those ribonucleotides link together to form a polynucleotide strand, one that performed some kind of useful function, all under prebiotically plausible conditions.

See, that's an example: not a definition.

DNAunion: Hey, if you can make RNA from scratch under prebiotically plausible conditions using just amino acids, go for it!