reply to post by windword
Yeah, sorry, that is science-speak. I'll try to interpret. She's saying there are basically two camps as to what came first in the evolution of
(1) heritable information (genes that would be either RNA, which is more likely to have been in the pre-life soup since it is simpler than DNA)
(2) the ability to copy that heritable information - an enzyme that copies RNA
In this paper, she reviews all the possible theories and combinations of what could have come first and concludes that none really works if evolution
were required to help life begin.
Let me back up and explain that in life as we know it, enzymes (proteins with function) are encoded for by RNA (actually in DNA but then in RNA). And
yet enzymes are responsible for copying AND interpreting that RNA- based code!
It is a chicken-egg kind of scenario. Iris is also saying that as life developed, it likely required evolution. Evolution meaning a system
(infrastructure) that can adapt to its surroundings and the better adaptation survives and is therefore selected in future "generations." So,
evolution requires some heritable information to be copied and passed on as well as enzymes to do the copying and passing on...chicken-egg.
So Iris is saying in the (2) scenario, how could an enzyme evolve to copy RNA if there was no RNA to copy to begin with? And, how could "evolution"
(natural selection) have selected for an enzyme to function at all if there was no RNA to code for that enzyme?
She goes on to assert that RNA (a polymer of a simpler monomer form of RNA) is not likely to have existed in that pre-life soup of molecules, the (1)
She actually represents a dissenting viewpoint in early life origin. What's interesting is that she proposes that it is not likely RNA could have
existed in this early soup but MANY RESEARCHERS DISAGREE - many researchers think based upon the most current data, that the monomers for RNA could
have existed in that pre-life soul. And similarly, researchers think enzymes could have existed at the same time. But RNA is supposed to encode for
Many researchers think these copying/elongating enzymes could have existed completely independently of RNA monomers and were randomly copying and
"playing" with these RNA monomers, threading them into polymers, just by random chemical interactions, until, amongst the trillions and trillions of
resulting newly created RNA polymers lead to the creation of enzymes with function (the same function or different).
Another camp of researchers that she didn't even discuss think, well, we know that now there are RNAs that have function like enzymes, called
ribozymes. Maybe these ribozymes were the first functioning enzymes that played with their RNA monomer-cousins to create a polymer-RNA. They can
move RNA around, cut it into pieces and even have been shown to re-assemble RNA! So maybe (1) and (2) co-existed as RNA...
And remember, some kind of enclosure still had to develop - like a micelle or lipid bilayer - to eventually encase these RNAs and enzymes, which would
have evolved into the "cells" we know today. She doesn't even talk about that at all either.
Nevertheless, I think her viewpoint is interesting and she makes the point that it is important to explore and match all possible theories with the
most current data available. The question is, did SHE include all of the most current data?