Origin of Life

[Spiff]

In reading the recent seemingly ill thought out thread on evolution, it got me thinking 'whoa wait a minute, evolution doesnt mention the origins of life, does it?'

Well maybe it does, i dont know. I assume not

So anyway I looked the topic up on the Wikipedia, and indeed yes there is a debate and numerous theories/models for the origin of life (on this planet, naturaly)

Most of it (me having only done Biology at Higher level a few years ago, in Scotland if youre wondering what 'Higher' means) is way over my head, so i'll not even try and paraphrase the writing.

From Origin of Life

There is no truly "standard" model of the origin of life, however most currently accepted models build in one way or another upon a number of discoveries concerning the origin of molecular and cellular components for life, which are listed in a rough order of postulated emergence:

1. Plausible pre-biotic conditions result in the creation of certain basic small molecules (monomers) of life, such as amino acids. This was demonstrated in the Urey-Miller experiment by Stanley L. Miller and Harold C. Urey in 1953.

2. Phospholipids (of an appropriate length) can spontaneously form lipid bilayers, one of the two basic components of a cell membrane.

3. The polymerization of nucleotides into random RNA molecules might have resulted in self-replicating ribozymes (RNA world hypothesis).

4. Selection pressures for catalytic efficiency and diversity result in ribozymes which catalyse peptidyl transfer (hence formation of small proteins), since oligopeptides complex with RNA to form better catalysts. Thus the first ribosome is born, and protein synthesis becomes more prevalent.

5. Proteins outcompete ribozymes in catalytic ability, and therefore become the dominant biopolymer. Nucleic acids are restricted to predominantly genomic use.

The article goes on to discuss the probability of life forming on Earth by itself, the Miller Experiments (an attempt to recreate the early atmosphere of Earth, as it was believed to have existed at the time), and a couple of other models, namely:

Clay theory
A hypothesis for the origin of life based on clay was forwarded by Dr A. Graham Cairns-Smith of Glasgow University in 1985 and adopted as a plausible illustration by just a handful of other scientists (including Richard Dawkins). Clay theory postulates complex organic molecules arising gradually on a pre-existing, non-organic replication platform - silicate crystals in solution. Complexity in companion molecules developed as a function of selection pressures on types of clay crystal is then exapted to serve the replication of organic molecules independently of their silicate "launch stage".

"Deep-hot biosphere" model of Gold
A controversial theory put forward by Thomas Gold in the 1990s has life first developing not on the surface of the earth, but several kilometers below the surface. It is now known that microbial life is plentiful up to five kilometers below the earth's surface in the form of archaea, which are generally considered to have originated around the same time or earlier than bacteria, most of which live on the surface including the oceans. It is claimed that discovery of microbial life below the surface of another body in our solar system would lend significant credence to this theory. He also noted that a trickle of food from a deep, unreachable, source promotes survival because life arising in a puddle of organic material is likely to consume all of its food and become extinct.

and finally...

"Primitive" extraterrestrial life
An alternative to Earthly abiogenesis is the hypothesis that primitive life may have originally formed extraterrestrially (note that exogenesis is related to, but is not the same as the notion of panspermia). Organic compounds are relatively common in space, especially in the outer solar system where volatiles are not evaporated by solar heating. Comets are encrusted by outer layers of dark material, thought to be a tar-like substance composed of complex organic material formed from simple carbon compounds after reactions initiated mostly by irradiation by ultraviolet light. It is supposed that a rain of cometary material on the early Earth could have brought significant quantities of complex organic molecules, and that it is possible that primitive life itself may have formed in space was brought to the surface along with it.


Ok then, the point of all this, i was wondering if anyone here had any opinions of their own, or opinions on any of these theories, or just general comments?

[MasterAdnin]

In reading the recent seemingly ill thought out thread on evolution, it got me thinking 'whoa wait a minute, evolution doesnt mention the origins of life, does it?'

Thanks.

MasterAdnin

[Darth Wong]

It is a common misconception that evolution theory explains the origins of life. Darwin's book was called "The Origin of Species", not "The Origin of Life". Evolution requires life to exist already before it can work.

For the origins of life, we need wholly separate theories. At the present, we have several candidates which can potentially explain what happened, but we cannot reconstruct exactly what happened. Religious types often try to use this ambiguity to argue that it must have been God, but as one pundit put it, if you find a dime in your couch and can't explain how it got there, you don't have to assume God put it there.

[BassV2]

It is a common misconception that evolution theory explains the origins of life. Darwin's book was called "The Origin of Species", not "The Origin of Life". Evolution requires life to exist already before it can work.

Spicies = Life
The Origin of Species = The Origin of Life

[alman9898]

the origin of species does not equal the origin of life. If you looked at the listed theories, then you'd see the difference. There's a difference between evolution and the origin of life - one describes the process of a change in the gene pool of a population over time, the other describes the chemical reactions that spawned the first organisms.

[Darth Wong]

Spicies = Life
The Origin of Species = The Origin of Life

You seriously need to start reading actual science books instead of creationist websites.

[Trebonius]

It is important to note that activity was far greater in the early solar system. Thus you would have interaction between objects frequently, including meteor bombardement, merging of lesser bodies, and even the shattering of moons and maybe planets.

The turbulent early stages of our solar system, would destroy anything but the most primitive traces of life. Meteor impacts would not allow stability on any world.

But any organic trace material would also likely be spread around, with the increased probability of interaction between all these objects yet to calm down into a more final pattern, or indeed merge together into their final form.

Exchange of primitive organic material between worlds, would be no problem as I see it. This would be the initial stage. The seeding of life.

[Spiff]

So what do people think? Space rocks bringing organic compounds? Its kind of puzzling given how volatile earths past was that anything ever had a chance to evolve

[Darth Wong]

So what do people think? Space rocks bringing organic compounds? Its kind of puzzling given how volatile earths past was that anything ever had a chance to evolve

Actually, most scientists studying the primeval period agree that there is a high probability that life started and was then destroyed several times on Earth before it took hold, during the early period when Earth was being regularly struck with enormous asteroid impacts (we're talking about impacts measuring in the billions of megatons here, thus making a nuclear war look like a popgun).