Pre-biotic soup
PaleoFreak coments on the level of understanding of natural selection theory. Doing so is like asking for somebody to come and tell you "the theory doesn't fit to me because...". Alas, that's what's happened, and it was about one of the most recurrent, interesting and harsh topics of all -- evolutionary theory may explain life's diversity, but what about its origin itself?
Abiogenesis --the generation of life from non-living matter; i.e 'spontaneous generation' well understood-- is Terra Incognita. There are a few theories around, but all of them include to some extent a key element: the rise of self-replicating self-organized systems. For some theories, the first systems of this kind were metabolic networks; for others there was a RNA world. In fact, it little matters. The thing is that once we have such a system working, we have life and then evolutionary theory starts playing a role.
I say that it doesn't matter because once an evolvable system has risen in the first place, it MUST evolve the features common to all modern life forms; all theories trying to explain the origin of life have to converge to this point.
Therefore, abiogenesis theories main point is to explain how this first 'living' system can appear from physico-chemical reactions alone. In contrast to what happens with the explanations of how modern-day life can evolve from the first living system, abiogenetic theories are dramatically different. Since plain chemical systems do not evolve (there must be heredity for that, and for that there must be self-replicant chemical systems; those aren't just 'plain' chemicals, they are far more complex), we cannot explain how from an abiogenetic scenario we can get into another.
However, all of them have something in common. The raw materials (how do those arise is subject of yet further discussions) are: aminoacids, simple sugars, nucleotides... everything we are taught in our first biochemistry lesson at school. And all of them have the same problem: how the heck can you get stable polymers from that?
Fairly easy, as it may seem. A recent paper (Leman L, Orgel L, Ghadiri MR (2004) Carbonyl Sulfide-Mediated Prebiotic Formation of Peptides. Science 306(5694):283-286) proves that cabonyl sulfide (COS), vulcanic gas, can catalyse peptide formation when pumped through a solution of mixed aminoacids, and doing so at room temperature in a matter of a few hours. The authors have tested a number of different reaction conditions and the results are just amazing.
Abiogenesis --the generation of life from non-living matter; i.e 'spontaneous generation' well understood-- is Terra Incognita. There are a few theories around, but all of them include to some extent a key element: the rise of self-replicating self-organized systems. For some theories, the first systems of this kind were metabolic networks; for others there was a RNA world. In fact, it little matters. The thing is that once we have such a system working, we have life and then evolutionary theory starts playing a role.
I say that it doesn't matter because once an evolvable system has risen in the first place, it MUST evolve the features common to all modern life forms; all theories trying to explain the origin of life have to converge to this point.
Therefore, abiogenesis theories main point is to explain how this first 'living' system can appear from physico-chemical reactions alone. In contrast to what happens with the explanations of how modern-day life can evolve from the first living system, abiogenetic theories are dramatically different. Since plain chemical systems do not evolve (there must be heredity for that, and for that there must be self-replicant chemical systems; those aren't just 'plain' chemicals, they are far more complex), we cannot explain how from an abiogenetic scenario we can get into another.
However, all of them have something in common. The raw materials (how do those arise is subject of yet further discussions) are: aminoacids, simple sugars, nucleotides... everything we are taught in our first biochemistry lesson at school. And all of them have the same problem: how the heck can you get stable polymers from that?
Fairly easy, as it may seem. A recent paper (Leman L, Orgel L, Ghadiri MR (2004) Carbonyl Sulfide-Mediated Prebiotic Formation of Peptides. Science 306(5694):283-286) proves that cabonyl sulfide (COS), vulcanic gas, can catalyse peptide formation when pumped through a solution of mixed aminoacids, and doing so at room temperature in a matter of a few hours. The authors have tested a number of different reaction conditions and the results are just amazing.
posted by BioMaxi at 4:52 pm
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