scigirl

Christ, DNAUnion, I think we can assume some basic facts. When someone is talking about evolution, they mean heritable change over time.



scigirl

scigirl

I was going to post something similar.

When you are talking about inheritance at the cellular level (i.e. what abiogenesis would deal with), epigenetic mechanisms become extremely important. No one is denying that speciation and that sort of evolution involves our friend DNA. But at a microlevel, mechanisms like methylation, and all those lipid effects discussed earlier, DO become important. For instance - development of eggs and sperm. Both oogenesis and spermatogenesis involve the same DNA separation mechanisms. However, due to unequal proportioning of the cytoplam in the egg cells, and the loss of the cytoplasm in the sperm cells, the zygote gets 99.9% mitochondrial and mRNA 'inheritance' from the mother.

scigirl

DNAunion

DNAunion: Hmmm....then why didn't that person just say that? Why did he/she say biological evolution was simply "change over time"?

I was pointing out what I saw as ironic. He/she was basically belittling the other person for not knowing what evolution was, and in the process told us what evolution was: but as stated, it wasn't even close.

DNAunion: See, that's wrong.

DNAunion

DNAunion: Scigirl, I was wondering about your opinion of the statements on proteinoid microspheres I made earlier in this thread (first page, about 10 posts down: it was my first post in the thread so you can use CTRL+F to find "DNAunion" to take you right to it).

scigirl

Ok fair enough.

As to your assessment of protein microspheres - I really don't know that much about them. Your assessment sounds right on. I would add, though, that several phenomenon probably played a role in creating the first replicating life form. I'd buy a theory that lipid microspheres were perhaps the first replicating 'cell' (I use the term loosely), then somehow RNA got incorporated into them, and so on.

But I don't feel very qualified to analyze any abiogensis theory since I don't have the background and unfortunately haven't had much time to read the relevant papers and such.

scigirl

pz

Oh, please. Any time someone has to express a brief definition of biological evolution, it's going to be incomplete, and a petty pedant can nitpick to a ridiculous degree...especially if they want to ignore the context and the general significance of the comment. You do not win points for trivia here.

DNAunion

DNAunion: Incomplete and completely off base are two different things. Scigirl did a pretty nice job by adding just one word to the original statement!

And here's another brief definition of biological evolution that's pretty good: changes in allelic frequencies in a population across generations.

DNAunion: I don't win ANYTHING here with you being a moderator. Hell, I don't even break even!

Let me guess, it was I who started the partial flame up between Principia and me in the other thread...right pz?

Principia

More to the point, if DNAunion insists on being uncharitable towards others, I see no reason why he should complain when the same standards are applied to him.

DNAunion

DNAunion: Soap bubbles in a bath tub will replicate if mechanical action breaks them apart, and the split bubbles will have a similar composition to their parent.

DNAunion: Soap bubbles preferentially add molecules of their own kind (amphiphilic molecules). And since soap bubbles replicate and the daughter bubbles inherit the traits of the parent....I guess soap bubbles are alive...right?

scigirl

I'm having a tough time understanding your argument here, DNAunion.

Soap bubbles exhibit replicative characteristics that would have been important in the replication of early cell membranes. That's my take on it.

I think about it this way:

IF it is true that cells emerged on the Earth without the necessity of guidance from some deity or alien, THEN there must be chemical and physical explanations as to how this could have occured. So - can we show that DNA and RNA can self-replicate? Probably. Can we show that proteins are capable of assembling into complex structures? Definitely. Can lipid membranes assemble and disassemble such that two bubbly things can come from one bubbly thing? Yes they can. Put all this stuff together and you have a cell.

Now, does that mean that any replicating piece of RNA, or spontaneiously assembling protein complex, or splitting off-lipid, is alive? No, no-one is saying that. These phenomenon simply show that as far as we know, there are no physical or chemical barriers to life assembling. Thus - abiogenesis could have happened without the need of a non-natural explanation.

Maybe it would help, DNAunion, if you could outline what your position is regarding the possibility or impossibility of abiogenesis.

scigirl