Dark Star Wrote:
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>Another good post! This discussion makes interesting reading. What I want to zero >in on here is the evolution part--particularly the lack of a mechanism to explain >how new species arise. So here it goes:
Lack of a mechanism? That's interesting. That's actually why 'intelligent design' isn't a scientific theory, but whatever.
>I know you already know this, but let's start here. Biologists define different >species as being animals that cannot interbreed.
Not quite - after all, were this true, ring species would not exist. In fact, ring species would be entirely incoherent.
>So a giraffe and a monkey can't produce fertile offspring (if they can breed at >all), thus they are different species.
Uh, this isn't quite the whole story. They are a completely different order, not simply different species under the same genus.
>Dogs, on the other hand, even though they might look quite different, can >interbreed and produce fertile offspring.
Right, they are of the same genus.
>So my question back to you: what is the sequence of chemical reactions that >cause offspring of parents to become a different species?
There isn't a specific sequence of chemical reactions - this is a strawman. Speciation occurs through a variety of mechanisms, the most frequent being isolation. One group of a population gets isolated from another and both groups diverge genetically until interbreed cannot be achieved. Interestingly there are multitudes of examples of this; ie, there are two groups of species that cannot interbreed yet there is a different group that can interbreed with them both. These species are called ring species.
>The fossil record does not "prove" that it happens, it merely "suggests" that it >might have happened. To prove it you have to go the extra mile, and show how our >ancestors--who had fewer genes and chromosomes than we do now--created offspring >with more genes and more chromosomes.
Proof is for math and alcohol - science works off of abduction and induction. Also, what is this nonsense about fewer genes and chromosomes - where's your evidence for this? You do realize that some bacteria have larger genomes then us, don't you?
>How did that happen? The truth is, no one knows.
Not so, speciation has been observed:
http://www.talkorigins.org/faqs/faq-speciation.html
How it exactly happened (ie, one species went to X while another went to Y) might not ever be known, however likely scenarios can be constructed.
>The fossil record is so suggestive of gradual evolution that scientists are >lured into thinking that it *must* have occurred. The fossil evidence is a good >starting point, but again, the chemistry that shows how a self-replicating >molecule can produce more advanced copies of itself has not been demonstrated.
Not yet, you mean, but the precursors are there. We have developed protocells, for instance. We also have many hypothesis as to how it occurred. We don't have enough evidence to suggest *WHICH* one did occur yet - but that doesn't mean it didn't occur: Here's a good breakdown of how it might have happened:
"In brief, it goes as follows. The formation of amino acids can occur (and have been experimentally demonstrated to occur) in a variety of ways in early Earth conditions, and can subsequently, then, give you proteins (for example - water, sulfur, hydrogen and carbon monoxide give you acetic acid, more carbon monoxide gives rise to pyruvic acid, ammonia to that makes for alanine, and bingo, you're at a peptide). All well and good, but not quite the complete picture, yet. This is where the environment - in our case, hydrothermal vents - really come into play. All the available ingredients, plus a ready-made heat source, and you're looking at a life-making warehouse.
The most prevalent feature of the thermal vent model (aside from being an ideal catalyst for chemical reactions to take place) is the availability of methane, interestingly enough. It is empirically demonstrable that thermal vents on an early earth gave off more methane than they do today (which wouldn't actually be necessary for our purpose here, since they still give off an adequate ammount of methane in the present). Levels of hydrogen in the early atmosphere are now understood to be higher than previously thought. Hydrogen and methane in the atmosphere help give you hydrogen cyanide, from which you can derive your acgu bases. Top all that off with co2 leading to formaldehyde, and you'll end up with ribose, throw in some phosphate, and boom - you've got everything you need for some rna action to get going within a nice membrane-type environment. Provided, of course, that you have a membrane. And interestingly enough, it turns out that iron-sulfide minerals alone can very much develop a 'bubble' that can act as a membrane, and in doing so, creates a chemiostatic gradient (you can just think of it as a power supply, more or less).
The late Dr. Sidney Fox discovered something very important - the process by which certain amino acids form thermal proteins - what was at the time of his innitial discovery termed proteinoid microspheres. He replicated this process many many times in his lab, and discovered that different amino acids combine into different proteins naturally. It is not a random process, it is completely controlled (like most everything in chemistry) in short, essentially by valence and bonds between molecular structures involved. Meaning, the results are predictable. The mircrospheres could grow, could replicate sans DNA, responded to stimuli much like neurons do, and overall, exibit every characteristic of life as we define it in biological terms. When they form, they give off flavin as a by-product (for you non-biology folk, flavin is the basis for any metabolic system). MORE IMPORTANTLY - the oldest fossil evidence we have on planet earth goes back almost three and a half billion years. They are of microspheres that look exactly identical to the ones Dr. Fox was able to replicate. Nail in coffin."
>An analogy would be clear here, albeit it's imperfect. Suppose a million years >from now humans no longer inhabit the earth, and space aliens explore the planet >(work with me here, I know it sounds silly so far). These aliens dig around and >find a Model-T Ford. Then they find a 1950's-era Chrysler. Finally they find a >2000 Corvette. They then postulate that this planet at some point in the past >must have had a way for these cars to evolve into more technically advanced >models. They are convinced it happened even though they cannot explain how one >car can produce another one that is superior to it.
Yes, it's imperfect as their is no way for the cars to replicate. This also assumes that the aliens are sufficiently similar to us in technology - otherwise you fall victim to one of Hume's criticisms of the argument from design.
>That is where we are with evolution.
Uh, no, not really. We know how animals reproduce, how mutations occur, and how mutations are naturally selected.
>Sure, there's fossils. Sure, it clearly shows that more advanced life forms >followed simpler life forms. Sure, we know that chimpanzees and humans (two >different species) share many common genes--just like two cars built in the year >2000 would be quite similar. But none of that makes any difference until Science >can demonstrate exactly how a species (or a population of individuals) can >produce offspring that are more advanced than itself. We don't see that >happening today, for example: where are new species being created on the planet >today?
"Advanced" is an anthropomorphism. It's a value judgement that you are giving a species - it is not found in nature.
Species produce offspring that are different then themselves by having sex. They are combining their genetics with another individual of their own species which will create different a different combination of genetic information.
As for new species today, all one has to do is look. Here's one:
http://www.nmsr.org/nylon.htm
>How does DNA (a self-replicating molecule) not only replicate itself, but >produce DNA with more genes and more chromosomes? The fossil record does not >show how this happens, instead, it suggest that it might have happened. >Scientists have no alternate explanation for life, so they cling to their faith >that, sometime in the future, such a mechanism will be discovered.
The link I gave above provides some illumination. Further, Chromosomes can fuse together, they can duplicate, they can change in a variety of ways.
Of course the fossil record doesn't show this - that is a strawman. The fossil record regards bones, not genes!
You are simply not up to speed on current biological or biochemical research. You made a number of false claims and a number of claims that can be refuted with a little research.