it was argued that evolution was a scientific theory, albeit a rather believable scientific theory. I guess I can buy the theory of evolution, or more specifically, the theory of natural selection.
I think one of the points the OP made was not properly addressed in that thread though.
That is, the theory that if you mix a little bit of lightning with the proper amino acids, life will spring from a chemical reaction. (I’m sure I oversimplified things here, but I think you get the gist of my statement).
No one has ever created life from a chemical reaction in a laboratory, have they? So why do we believe life can be formed this way?
Although some progress has been made on coming up with better ideas on how life could come from non-living material than “a lightning bolt hit a puddle full of goop”, I don’t think anyone is claiming yet that we have anything like as complete an understanding of abiogenesis as we do of the basics of evolution by natural selection. That said, a couple of broader points. One, just because we haven’t been able to do something in the laboratory doesn’t mean it didn’t happen. They’ve been saying controlled nuclear fusion is “20 years away” for at least 30 years now, but no one doubts that nuclear fusion reactions are what makes the stars shine. Secondly, there must be some explanation of where life came from. “Intelligent design” as an explanation tends to run into a sort of chicken and egg problem. If the intelligent designers are merely hypothetical extraterrestrials, then we have the obvious and immediate problem of where they came from. Short of finding a message saying “Made in Zeta Reticuli” encoded in the DNA of all living organisms, Occam’s Razor would seem to suggest that, given that Earth has life, and we haven’t found life anywhere off Earth, the simplest explanation is that Terran life probaby arose somehow on this planet rather than elsewhere. If the Intelligent Designer is God, then we still have the philosophical question “Where did God come from?”, and worse, we’ve now moved beyond the proper arena of scientific hypothesizing. As an explanation, “God did it” has the problem that it can be used to explain anything, and correspondingly, from a scientific point of view, explains nothing. Theologically, the “God of the gaps” runs a great risk of causing embarassment down the road when or if someone finally does come up with a good naturalistic explanation of the “gap” you’re trying to fill.
Firstly, evolution and abiogenesis are completely seperate subjects. Evolution deals with how populations adapt over time and speciation. Abiogenesis deals with how non living chemicals became living organisms. Evolution is very strongly supported by mountains of evidence, abiogenesis consists of a large number of plausible theories but little in the way of experimental evidence. This isn’t suprising. A huge number of chemical processes is required to form proteins, RNA and DNA. It’s unlikely to be something you can replicate in a lab (non-life -> life), unless you perform a few billion experiments over vast periods of time.
If you’re interested in this sort of thing, I recommend the Talk Origins website. They can explain these things far better than I can.
Life might be everywhere in the universe, IIRC the pansperma theory, in the form of simple single cell beasties dormant in rocks drifting through interstellar space.
Though it doesn’t go into how life started initially, it does give you lots of interesting places for life to have started, and a lot more time then just earth and approached the saying if you give an infinite numbers of apes an infinite amount of time, they will somehow make a copy of Romeo and Juliet.
Also a scaled down theory is that our life started on mars, a impact there moved some material (and lives) to earth.
Both of these suggests that life starting ‘force’ may be nothing like we have on earth, and nothing like we are considered.
I’m a physicist, not a biologist, but I took a module called “life in the universe” in my final year at uni.
From what I can remember, the current debate is which came first DNA/RNA or the actual cell membrane (don’t know the actual name of this). Apparently there is pretty much an even split between the two camps.
The arguments seem to be fairly circular to me, simplified they are as follows:
DNA/RNA is fragile and complicated and would need to evolve first from long protein chains, but would not survive without protection.
The cell membrane evolved first and then evolved DNA/RNA, the fault with this seems to be that without the need to protect the DNA what need would the membrane have to exist.
I suspect that the truth is more complicated than either of these postulates suggest.
The suggested text for the course (which I still have not read completely was “The Origin of Life” by Paul Davies formerly called the Fifth Miracle.
I will try to read it and see if I can come up with a better disription of the current theories.
Abiogenesis is pretty solid these days, and as MEB says, just because it might occur over timescales longer than those feasible in a lab does not impugn the basic premise.
The main difficulty with Miller and Urey’s experiment was the stability of some of the molecules, and Earth was indeed a rather unstable place in these terms. However, outer space allows for the formation of these complex but stable organic compounds which have indeed been observed. These compounds have even been observed being transfered to Earth via comets, such as in Kerala (PDF) in 2001, which might even have contained simple “spores”.
There is nothing ‘Flat Earthy’ whatsoever about the idea that comets covered in complex organic molecules formed spherical proteinoid structures upon collision with Earth, in which further chemical rections took place, eventually yielding the self-replicating molecule DNA.
Notice that I prefaced theory with the word ‘scientific’. As for the flat-earth idea, that was never a scientific theory to my knowledge. As another doper points out, it doesn’t make any hypothesis’s nor are there any tests in favor of it.
Panspermia - the seeding of life here from out there. But that begs the question of where THAT life came from. I hadn’t thought about what you posted, SentientMeat, regarding the genesis of chains on comets.
One thing missing from our lab experiments is time. The electrictrified goop sat around for billions of years before replicating organisms began competing for resources. Also, one argument against abiogenesis happening today in modern experiments is that competition for resources is so fierce, even at the micropscopic level, that new life doesn’t have a chance.
I know it’s a bit of a nit pick but the first life forms identifiable in the fossil record have been dated to about 3.8 billion years ago.
The solar system formed about 4.5 billion years ago. This leaves about 700 million years in which life formed (look up stromatolites). The fact that life did bugger all but photosynthesise for about the next 3.2 billion years is the bit that puzzles me.
It’s competition. I think it took those billions of years for the bugs to reach a level of density where competition became fierce enough to allow beneficial mutations that gave an advantage to proliferate, thereby causing a bigger explosion in diversity.
Not at all. Nothing in science is ‘rock solid’ as science is by it’s nature a tentative enterprise.
My question to you stems from your sentence: “it was argued that evolution was a scientific theory, albeit a rather believable scientific theory.”
Which is confusing because it suggests that scientific theories rely on belief to some extent and that because the theory of evolution is a scientific theory that somehow the credibility was effected.
So I said, what else would it be, other then a scientific theory?
You then said “Well, the theory that the earth was flat is one, for instance.” Which is probably considered a ‘theory’ to laymen, but it’s not a scientific theory at all. Scientific theories are actually different from how laymen use the term ‘theory’.