incorygible
Posts: 374
Joined: Feb. 2006
|
| Quote (ericmurphy @ Oct. 02 2006,13:37) | Dave, so what if it's a total guess? So what if it's totally wrong (especially since no one will ever know for sure)? What does it have to do with your point? You expect some living eukaryotes to be more closely related to living bacteria than others are. Therefore, you think that Denton's chart, which shows no such thing, proves that evolutionary theory is wrong.
But you're wrong, Dave, because all living eukaryotes are equally distantly-related to living bacteria. They're also all equally distantly-related to the bacteria of a billion years ago. So even if Incorygible is completely wrong about the sequence difference between ancient and modern bacteria, that helps your case not one iota. So why are you crowing about this statement? It has absolutely nothing to do with anything, whether it's right or wrong. |
Let's clear up any confusion here (e.g., Re: "even if Incorygible is completely wrong about the sequence difference between ancient and modern bacteria").
What I said was:
| Quote | | Yes, in a truly neutral region of DNA (i.e., a molecular clock), a 500 myo bacterilum is MUCH different than a modern bacterium. The difference between old bacterium and new bacterium would be very similar to the difference between human and old bacterium IN THIS NEUTRAL REGION. If you want to talk about non-neutral (e.g., coding) regions (does that remind you of a heading in the human-chimp table?) that are under the purview of natural selection, we can expect that modern bacteria are more similar to ancient bacteria than humans are (but we can't know how similar, unless we can study fossil morphologies to make educated guesses about certain genes). |
The differences I am speaking of in the second sentence are in the TIMES (they are "clocks", after all) read from the respective molecular clocks (Dave will see something similar -- tau-species and tau-genome -- in the Nature paper I sent him). The amount of genetic divergence would, necessarily, be great enough (and resolved enough) to read these times. Furthermore, there would have to be cause to believe that the region of DNA in question was truly selectively neutral and had remained such since divergence. Finally, there would have to be cause to believe that mutation rates were regular and conserved across comparisons. In other words, I tried to simplify to Dave's grade-school level by omitting any talk about mutation rates (why they would be different for prokaryotes vs. eukaryotes), what would comprise truly neutral DNA, whether it exists in prokaryotes, generation-times, and other considerations. But I was very clear that I was talking about a region of DNA that would constitute a molecular clock -- NOT any region of DNA, and certainly not ALL the DNA.
I did not say that any particular sequence difference (especially across the entire genome! between ancient bacteria and modern bacteria vs. human and ancient bacteria would be the same. I did not say that we have such a "true" molecular clock up to the task.
I was illustrating that a molecular clock, in principle, would (practically by definition) reveal the same time since divergence from ancient bacteria for both modern bacteria and humans. This is not a guess. It is, in fact, a bit of a truism if you understand phylogeny. For Dave, it's a momentous discovery (especially when you misrepresent it!.
I say this right now, so I can link to it when Dave inevitably claims (AGAIN) that I said something along the lines of "the modern bacterial genome is as different from the ancestral bacterial genome as the human genome is".
I did not say this. This is detailed clarification that I did not say this.
I accept any responsibility for forgetting that one can have no more subtlety than the average sledghammer when trying to teach Dave anything.
However, following this post, any further claim by AFDave suggesting that I said anything remotely similar to "modern bacteria are as genetically different from ancient bacteria as humans are" will be a deliberate misrepresentation (read: a lie).
|
