Farren

I've encountered the "incredibly unlikely" argument against the occurance of the first living thing and subsequent natural selection to produce contemporary life time after time.

What strikes me is that the argument always seems premised on the fact that one is allowed to ignore the rest of the universe in considering likelihood, and consider the earth alone as a special case.

Are there any suitably illuminated astrophysicists or chemists here who can provide the figures/calculations required to determine the likelihood of organic chemistry occurring somewhere in the entire universe over its presumed age?

Coragyps

I'm a not-very-illuminated chemist, and I can tell you for pretty damn certain that the odds were good enough to make life happen at least once.

As far as calculating odds, I feel that's a fool's errand: we don't even know what set of reactions had to happen just on this planet to lead to the first self-replicator. We don't know what percentage of stars have planets in a liquid-water zone; we don't know if liquid water is a for-sure requirement for life; we don't know way too many things to even take a good stab at a calculation.

A few things that we do know are that molecules as complicated as the vitamin niacin and many amino acids are formed from sunlight, cyanide, carbon monoxide, and water in meteorites that never saw anything alive. We know that fatty acids can form in basalt. We know that various simple compounds like these will self-assemble into little blobs that look, and in some ways even act, like bacteria.
The "incredible odds against" that Fred Hoyle talked of, and that creationists like to quote, are pretty meaningless - the bookies making them up know much less about what numbers to try than the folks like Stanley Miller that are actually looking at possible pathways to the first life - and I don't think many of the latter would even guess.

Friar Bellows

The likelihood of life arising somewhere in the universe is 1: that's us. The likelihood of life other than our own is between 0 and 1. At the moment, scientists can't do better than that; we're completely ignorant on the question. Nevertheless, quite a bit of thinking has gone into the topic, and, in my opinion, it's better to be completely ignorant on a higher level than that of your mates at the pub, so try googling these terms: "Drake Equation", "Exobiology", "Astrobiology", and "SETI". A couple of links:

http://astrobiology.arc.nasa.gov
http://directory.google.com/Top/Scie...ife/Exobiology

Oh, I just noticed that you used the term "organic chemistry" rather than "life". I seem to recall that organic means complex carbon chemistry. Then the likelihood is 1. Astronomers have detected all sorts of organic chemistry with their telescopes. Things like polycyclic aromatic hydrocarbons, polyenes, and quite probably amino acids (the latter in meteorites, but they could conceivably form outside the solar system, see: http://www.astrochem.org/amino.html).

Secular Pinoy

The Secular Web library has this good overview of "unlikely odds arguments" creationists make: Are the Odds Against the Origin of Life Too Great to Accept? by Richard Carrier.

beausoleil

Since we don't know how big our universe is, we can't calculate the likelihood of anything happening in a universe the size of ours

jayh

The after-the-fact calculation of odds is totally irrelevant.

Everyone of us is the resut of incredibly unlikely odds--hundreds of millions of sperm... the odds that a particular one would reach a particular egg at the right time are stupendous, yet that does not disprove that anyone of us exists.

j

Farren

Thanks everyone for your responses.

On the last one, a friend argued exactly this with me today. That the after the fact odds are 100%. In fact we were both drunk (I'm still reeling) and it got quite savage

However, the creationist argument is not the odds of existence in the face of self evident... existence - it is the odds of a particular cause being likely.

To answer it convincingly (to a creationist - I am long ago convinced) requires addressing this in an articulate manner.

js_africanus

I'm not so sure about that....

Anyway, for the OP, you may benefit from checking out Science & Creationism edited by Ashley Montagu. Apart from being a great read, there is a chapter that deals with that question. Given the fact that certain chemicals existed, the chance of life occuring is near unity, IIRC. I don't have it handy, I can't point out which chapter.

deano

odds dictate,if something occurs somewhere in the universe(life on earth),it will be happening elsewhere in the almost infinite scope of existence.we are not special and devoid of the laws of physics.

xorbie

Actually, I rather agree with what jayh said, and while it is simple it is also profound. To say that something is "very unlikely" does not disprove or prove its existence, it only speaks of likelihood. The example he gave is also excellent. Could anyone actually argue that I don't exist because the odds of me getting these genes is so low, and do so with a straight face? I highly doubt it.

In terms of people, yes I think you would say that it is very unlikely that we are here on planet earth with this sun. But you have to consider that we would say the same thing were we on any planet, and this is not a proof that humans can't exist. Arguing that would be like saying "well the odds of X happening in any individual outcome is very low, so it can never happen, even if we have N outcomes, where N is some freakishly huge number". This argument would basically be saying that anything that probably won't happen will never happen. Sheer ignorance, and it shows an obvious lack of logical abilities and critical thinking capabilities.