Fossils and suchlike

Hi Jim Pemberton,

As always, thanks for your thoughts. I appreciate them.

I'd like to please respond to what you said:

Given the diverse range of morphologies in life on Earth, since observed morphology is the basis for genetic relatedness between fossil remains

I'm not sure "observed morphology" is always necessarily the sole or main "basis for genetic relatedness between fossil remains" if that's what you're suggesting.

1. For one thing, if there's "genetic relatedness," then wouldn't this be based primarily on genetics?

At least as I understand it, though, the vast majority of fossils won't have enough genetic material to determine its "relatedness" to other fossils or beyond (e.g. where it fits in a phylogenetic tree).

2. I'm not sure if you're referring to the "observed morphology" of the fossil? Or, say, to the "observed morphology" of a living plant or animal or other organism, and somehow attempting to relate it back to the fossil?

3. More to the point, I would think other aspects could at times be equally relevant in determining a fossil's "relatedness" to other fossils. A few possibilities come to mind:

a. Where the fossil was found. Not just geographic location, but other aspects like sedimentary layer or if it was found in rock or under water.

b. The state or condition in which the fossil was found. The degree to which the fossil has fossilized. Or mineralized. Or the like.

c. If the fossil contained any "living" or non-fossilized parts.

d. If the fossil was found with other fossils.

e. If the fossil was found with other variables like sets of footprints (e.g. dinosaur trackways).

f. If the fossil made an imprint or impression that might have preserved other features of the fossil especially if the fossil itself was found less intact than its imprint.

g. And so forth.

4. "Observed morphology" may not always help determine "relatedness." Take convergent evolution. Say if we discovered fossils of a flying squirrel and a sugar glider. The fossils might share very similar morphological features. But neither is considered closely related to the other (e.g. one is a marsupial).

most scientists believe in common ancestry precisely because they recognize that spontaneous genesis of reproducible DNA isn't likely.

1. It might be pertinent to the topic if I start by saying I don't agree with neo-Darwinism. I've criticized it in the past.

2. Also, my original post didn't have reference to common ancestry as such. Rather I was referring to the origin of life. The first self-replicating molecule, as many scientists construe it, especially secular scientists.

3. There's a distinction between common ancestry or descent and universal common descent. All dog breeds share common ancestry since they're descended from wolves.

Generally speaking, I don't think most creationists would disagree with common descent, per se. However, they would (rightly in my view) take issue with universal common descent.

4. I don't think the predominant reason "most scientists believe in common ancestry" is "precisely because they recognize that spontaneous genesis of reproducible DNA isn't likely."

In fact, many scientists argue for some self-replicating molecule for the origin of life. I would think most secular scientists would argue for this or something akin to it.

Many if not most secular scientists seem to hold to some sort of primordial soup model which would involve certain preconditions as well as one or more molecules gaining the ability to self-replicate. They may not argue specifically for DNA as that molecule. Although the usual suspects do seem to be proteins or nucleic acids (e.g. RNA).

Of course, there are many other disparate theories. But if we had to pick one, then something like this would probably be it.

5. That said, not every scientist's opinion on the matter is equally relevant. A quantum physicist could be a poor person to adjudicate the question, whereas a biochemist might be better, for example. It depends on what we're talking about exactly.

6. Besides, if it were true most scientists "recognize that spontaneous genesis of reproducible DNA [if by this you mean a self-replicating molecule as the origin of life] isn't likely," then I would think this would be a reason to doubt universal common descent.

Otherwise, they would entertain the idea that spontaneous genesis of reproducible DNA happened multiple times on Earth and evolved into different unrelated types of organisms.

1. Perhaps I'm missing something, but I don't see how this follows from your previous statement.

2. Nevertheless, it's an interesting idea.

3. However, I suspect the average secular scientist wouldn't necessarily have a problem entertaining this idea. Various self-replicating molecules rather than a single self-replicating molecule acted upon by natural selection along with genetic mutations leading to all the diversity that is life wouldn't seem to entail too many significant changes to the modern evolutionary synthesis, I don't think.

They might even say, if it unfolded as you describe, the "different unrelated types of organisms" may each eventually become extinct until one was left such that it became our last universal ancestor. Or perhaps they each eventually evolved and became able to interbreed.

Again I don't necessarily think a secular scientist would be too bothered by a theory which incorporates multiple ancestors. For example, there are at present two main theories for the origin of modern humans: the Out of Africa theory and the Multi-regional theory. In the Multi-regional theory, modern humans would have genetic material originating from Homo erectus, Homo neanderthalensis (aka Neanderthals), and Homo sapiens. Some secular scientists advocate this sort of stuff, and I think most would probably be perfectly fine if it turned out the Multi-regional theory was true. (Although the majority favor the Out of Africa theory.)