Hypography Science Forums: Biochemist - Viewing Profile - Hypography Science Forums

Pyrotex said:

All true, and a good point. I still am surprised (and it seems somewhat counterintuitive) that after "carving into stone" so much of the standardized cell infrastructure, that we could generate such a remarkable diversity in body plans without significant alteration to the standardized machinery.

My opinion on this (completely unsubstantiated, of course) is that the tendency toward life (in fact toward the tree of life that we see) is intrinsic in the fundamental molecular structure of the basic molecules. That is, development of life is similar to the order created when solids crystallize. The difference is (of course) that crystallization happens rapidly, so we can test reproducibility.

I would hypothesize that if similar conditions arose again, we would get a very similar tree of life again, and arrive at a very similar "end point" again.

Bio

riper said:

Nice point, Riper. Darwin should probably have said something like "survival of the most opportune variant in the niche", but it doesn't quite roll off of the tongue as well.

Michaelangelica said:

This is a really interesting development, MA. Your point is valid, but since the retrotransposon activity is embryonic, it also suggests that genetic changes that would result in death of a fertilized ovum now will only result in death of an early embryo cell. Essentially, it raises the probability of embryonic survival, and increases the probability off a functional cell mosaic (whether good or bad).

Really interesting. Also, I never saw the numbers (noted in the summary) that L1 retrotransposons are 17% of the human genome. This is roughly six times the portion that transcribes proteins.

Bio

Pyrotex said:

This is undeniably true.

Pyro said:

Very likely to be true. And your argument above that higher phyla are less likely to branch is a strong one as well.

Pyro said:

Absolutely agree. But the core of the scientific method is prediction and falsifiability. If we posit gradualism based on serial incrementalism, we should either defend (or question) the predictions, modify the hypothesis, or throw it out.

I continue to think the argument for gradualism is weak. We have strong examples of genetic drift, but these seem to be cases of selection of recessive alleles. There is just so much assumption about how those recessive alleles got there.

Pyrotex said:

Gradualism does not require (or even imply) species or phyla need to go extinct slowy. Only that they accrue slowly. And the slow growth should be "reasonably" consistent (e.g., generally logarithmic) over long time horizons.

Pyro said:

I know you were joking on this, but it is true that new phyla actually may have shown up, and we missed them.

Pyro said:

This is a valid hypothesis, but it feels more like a postulate. It is a little tought to falsify. Further, we are accepting that speciation occured regularly over the last 500 million years, but no phylogenation. This alone seems to argue against the postulate that the "niches" were all "filled up". Besides, the niches that were vacated actually had "time" to be repopulated by similar phyla. We have had twice as much time since we lost them as it took to generate them.

Again, my only point is that this is not particularly consistent with gradualism.

Pyro said:

This seems completely at odds with the experimental data (such as we have it). There may well be a ceiling, but we would not expect the ceiling to fall. We might expect the phyla/species count to approach the ceiling asymptotically, but not to hit it and fall backwards.

Reiterating, I an not suggesting your suggestions are unreasonable. Just that they are not particularly consistent with gradualism.