Evolution in pieces.

This is actually a repost from another discussion forum, but I thought it might be worthwhile bringing it over here. One of the problems I see in the Evolution/Creation debate is the rather ill-defined nature of the word 'evolution'. What follows is my attempt to break it down into individual parts:Decent With Modification. The idea that all species alive on earth today derived from earlier species, changing by small steps each time. I consider this proven beyond any reasonable doubt. The fossil record unanimously supports it, DNA sequencing unanimously supports it.Single Common Ancestor. The idea that all life today shares a single common ancestor. Certain similarities in DNA across all life hugely supports this idea. That the exact same mechanism could arise independently multiple times is radically unlikely. The only possible exception is Viruses, who are only loosely categorised as life anyway (can only reproduce with help and all that), but even their RNA has a few tell-tale hints in it.Natural Selection. The idea that the major mechanism responsible for this Decent With Modification is the principle of Natural Selection. That Natural Selection occurs is almost unarguable, and research such as the infamous speckled moths experimentally verifies it. Unfortunately it is massively harder to demonstrate that it is responsible for the observed changes over time. What we can do is model the potential of Natural Selection mathematically and using computers. And indeed these both support the idea of NS being sufficiently capable. Since no-one has an alternative mechanism capable of this action, I accept NS as being the driving force behind Decent With Modification. While other actions almost certainly have an effect (genetic drift, for example), they are not responsible for the increase in Fitness, and Complexity, exhibited by life on earth.Historical Reconstruction. Working out which ancestor links to whom; tracing out the intricate paths of life on earth. This is the weakest part of evolutionary theory, while we can establish this in broad sweeps for most life and fairly precisely for those few species we have a good record for, the fossils record isn't complete enough to cover all life, and it is almost impossible to tell whether a fossil is a direct ancestor or a 'cousin' of that ancestor.Things which are not evolution (but are often lumped with it). Abiogenesis, the big bang, plate tectonics, solar system formation, radioactive dating, etc. These range from speculation (abiogenesis), to certain fact but unclear mechanism (big bang) to certain fact and clear mechanism (radioactive dating, and plate tectonics). But I shan't discuss them in detail here.

Single Common Ancestor, Mike, the single is important. 'Common Ancestor' can refer to the common ancestor of any two species. Single common ancestor refers to the ancient (~2 - 4 billion years ago) organism from which all modern life evolved.We will never find such an ancestor. If we did find it, we couldn't demonstrate it was the actual ancestor and not just another member of the same species, or that there wasn't an earlier common ancestor we just haven't found. Note that the single common ancestor is generally defined as the latest such organism.The common ancestor you seem to be talking about, is the common ancestor of Humans and Chimpanzees. To the best of my knowledge we haven't found a common ancestor for Humans and Chimpanzees. But that's another topic, so if you want to discuss it further I suggest you start a new topic?

Rubbish. DNA similarities are compatible with a common creator, but not evidence for one. And therein lies one of the most fundemental problems with Creationism; it makes no real predictions.Incidently how does a Common Creator differ from a common designer? Horses? Whales? Humans? Etc? Seems to me you're really not familiar with the fossil record. And how does surviving to reproduce have nothing to do with health or any other benefits? I'd say it was directly linked to it.

I assume you mean CR Woese? Do you have a reference for this refutation? I ask because doing a brief online search brought up this paper by CR Woese, O Kandler and ML Wheelis, from which I quote:"Within the last decade it has become possible to trace evolutionary history back to the (most recent) common ancestor of all life, perhaps 3.5-4 billion years ago."The references for this passage pass onto two further papers from Woese.

Careful, Crashfrog, species itself is a somewhat imprecise classification scheme - to the best of my knowledge there is no single clear definition of species.

Indeed so, but we must be careful of requiring a standard from the Creationists that we do not meet ourselves.

As I see it there should only be boundaries over which the 'kind' cannot cross. Defining kinds need not be easy for this to be so.The thing that really amuses though is that the creationist notion of kind has exactly zero biblical support.

I'm not trying to play Devil's Advocate here, but I am a big stickler for playing fair and respecting the other side (although as a few of my posts may indicate, this does make me an occasional hypocrit). This is particularly true in the evolution/creation debate. Our side is Science. Science works because it is so self critical, we must therefore apply as, or perhaps a more, critical eye over our own posts as we do over theirs.It seems to me that Crashfrog was asking for something from the opposition more definite than that which we define as useful ourselves. It also seems to me that there is a Creationist definition of kind: groupings that are 'microevolutionarily' distinct. That there is not evidence of any such groupings, and indeed that all the evidence would seem to suggest such groups do not exist is evidence against the Creationist but the failure of the Creationist to provide a clear, easily-applicable definition or list of 'Kinds' is not.