Nowhere357

The human embryo goes through a stage where it has gills and a tail. (Also, we all start off female, which explains nipples on guys.)

This seems clear evidence of evolution over creation.

It shows how life evolves, given that life exists. It does not, however, show that life arose from the dead muck.

IOW the laws of physics do not indicate life. In order to study life (biology, psychology) first we must assume life exists.

What does this mean? Should I duck?

Wounded King

It sounds as if you are talking about some form of Haeckel's theory of recapitulation, this is sticky ground. Many creationists feel that because 'ontogeny recapitulates phylogeny' is generally accepted to not be strictly the case that this therefore menas that embryology can tell us nothing about evolution, this is obviously quite wrong.

Human embryos do not actually have gills they do have structures similar to those which develop into gills in fish, and these structures are thought to be homologous.

It has been pointed out many times on these boards that evolution and abiogenesis are not one and the same thing, it seems redundant to assume that life exists since we already have so much abundant proof.

To say that the laws of physics do not indicate life seems a bit strange, the laws of physics certainly allow life to exist and do not in any way inhibit it. I'm not sure that the laws of physics of themselves indicate anything much.

Nowhere357

I think you are agreeing that embryonic stages are evidence for evolution.

Okay, but I think this is a distinction w/out a difference.

The first part of this statement seems to say that embryonic stages are not proof of evolution - I agree. Evolution and natural selection is a powerful theory that stands on its own and needs no help from me. I'm a big picture guy, and I find embryonic stages to be strong visual evidence that life evolves.

The rest of the statement indicates that you've missed my point. The skeptic POV generally holds that evolution and the laws of physics are adequate to explain the origins of life. I am (with trepidation) claiming that view to be inaccurate.

Allowing life is not enough (clearly if physical law contradicted life, we would have to toss the whole thing and start over). If physical law is adequate to explain reality, then physical law must indicate life, and I don't think it does.

In order to study life, science first has to assume that life exists. Biology makes that assumption. IOW physical law explains evolution, given that life exists. Physical law does not prove that life arose from the dead muck, only that once arosen, life then evolves. The origin of life is still a mystery. The existence of life is still a mystery.

The Lone Ranger

With respect, I think you've missed Wounded King's point. Evolutionary theory assumes the existence of life, and cannot, therefore, explain the origin(s) of life. "Abiogenesis," as noted, is the study of how life originated. Of course, given that the origin(s) of life occurred some 4 billion years ago, it's highly unlikely that we'll ever be able to say for sure exactly how it occurred.

This doesn't mean that evolutionary processes are irrelevant to the origin(s) of life, however. It's certainly not the case that the first living cell arose through a random aggregation of molecules. Some selective processes were surely in action even before the first living thing arose. (The boundary between "alive" and "not-alive" is a very fuzzy one, by the way.)



Physical law does not, so far as we can tell, demand that life exists. Rather obviously, however, it permits the existence of life.

Yes, just as chemists would find it difficult to study atoms if they didn't "assume" that they exist. Really, though, this is somewhat backwards reasoning. Biology "assumes" the existence of life only inasmuch as one cannot explain something which doesn't exist. Biology is the study of life, including how living things change over time -- this is why the origin of life lies outside of the field of evolutionary biology. Once you've got living things, then biology can study them; before then, it's chemistry's domain.

Quote:

IOW physical law explains evolution, given that life exists.

No, physical law permits evolution; it does not explain it*. Evolutionary theory explains evolution.

Quote:

The origin of life is still a mystery.

Yes it is. We're working on it, though. (For the record, absolutely nothing has been discovered as of yet which suggests that life cannot and/or did not arise through purely natural processes, such as those which prevailed on the young Earth.)

* To clarify the point, it's important to keep in mind that physical laws are not explanations -- they only tell us how things behave under certain circumstances (assuming that our understanding of these laws is correct, of course). Theories are explanations.

Cheers,

Michael

Nowhere357

Good post, LR, thank you.

I miss points sometimes, but here I think I didn't. I haven't made my point clear, as I saw when "abiogenesis" was brought in, hence my comment. That is, "abiogenesis" is to "evolution theory" as "biology" is to "physics", and misses my point.

Evolution theory assumes the existence of life. Abiogenesis of course assumes e.t., and so assumes life. I think we agree. It is that presumption itself that I'm trying to focus attention on. I'm trying to show that life is a fundamental assumption of reality, right up there with space and matter, maybe.

I agree completely. A selective process, for example, might be crystal formation. And I'm glad to hear you mention the fuzzy boundary.

This also is key to my position. Again, the existence of life is assumed, at the most basic level of our understanding of the universe.

I hope now you can see my point. Atoms are a pre-requisite assumption to our understanding of reality. Atoms just
exist and that's where we start from.

IN the same way, the tendency of matter to form life, is a basic presumption of reality. I guess I'm saying that this tendancy is a fundamental physical law, in itself.

I agree with this, except for the 'backwards reasoning' part. It just looks that way because I bring a different viewpoint, a fresh perspective.

Again, I hope my point becomes clearer. All our knowledge presumes the tendancy of matter to form life; why then is that tendancy not considered a fundamental property of reality?

I guess I still see life as some sort of animating force. It looks to me as if life adds order and compexity to a system. Why is that not seen as a force or energy?

Claudia

Nowhere,
Can you please tell us your definition of what "abiogenesis" means? Definition as in a dictionary?

Wounded King

It is not at all a distinction without a difference, although it may be one without relevance to the thrust of your argument. It makes the difference between the strong sort of recapitulation which requires an embryo to go through the adult stages of its ancestors and the weak sort which merely requires that the development of an embryo reflect, in any of a number of ways, its evolutionary history.

It is the difference between a theory which has been proven wrong, was indeed shown to be wrong by Von Baer even before it was postulated, and which is consequently something creationists love, and one which goes from strength to strength the more we know of developmental and evolutionary biology.

Quetzal

abiogenesis = better living through (organic) chemistry

Wounded King

Dear Nowhere,

You say

I dont think any of our knowlege suggests a tendancy of matter to form life, this smacks of the worst sort of teleology. The fact that life appears, in one instance, to have formed from non living matter does not suggest that all matter tends to form life. If that were the case then we should expect life to be abundant everywhere that matter exists, so far we have only identified it on Earth and even here there is no evidence of an ongoing de novo formation of life from matter. Our current theories of the origins of life only require life to have arisen from non life in one particular instance, not for this to be a trend throughout the universe.

RufusAtticus

Human embryos never have gills. They have pharyangeal arches (gill arches) which in fish develop into gills and jaws, but in humans develop into jaws.