PaulN: “Contact Inhibition” is the broad term used to describe an observed event, in this case the observed stop-growth of cells upon making physical contact with one another.

That’s correct. But it’s more information than just a restatement that cell division stops.

PaulN: The mechanisms behind contact inhibition are still not fully understood, and in fact may not have anything to do with contact at all.

That’s correct. It may sometimes be more closely correlated with cell density.

PaulN: Which you have still ultimately failed to provide to any acceptable scientific standard of explanation for reasons that I’ve just explained.

“No more room in the skull” is a directly parallel explanation to “contact inhibition.” Both would leave many important details unstated or unknown, but it is not the same as not providing an answer as you suggest. And it is something that can be directly observed and studied. However, your additional questions concerning the details of that process are certainly reasonable.

PaulN: From what I’ve seen so far, there are a number of different complex mechanisms that contribute to contact inhibition, none of which I’ve read about so far fit evidentially into the grand claims of clumsy Darwinian synthesis, but rather fit the incredible trademarks of super-intelligent engineering, …

Actually, it ‘looks’ like something that evolved. But how it ‘looks’ to you or someone else is not a valid scientific test, of course. There’s still a lot unknown about this ancient transition, but there’s also quite a bit of research on the evolution of signal transduction. For instance, prokaryotes are dominated by single component systems with both input and output domains on a single protein, which is the type of intermediary expected by an evolutionary process.

PaulN: … as the extensive fossil record shows a collection of fully-developed and fully-functional body plans with little to no functional failures.

Of course not. The Theory of Evolution would not posit functional failures persisting long enough to be likely to leave fossils. The process of creating such a large, complex structure would be through viable steps. We have reasonable scientific assurance of this because of Common Descent, the observation of evolutionary mechanisms, and the many other established cases of evolutionary transition.

-
This review article should be available, albeit somewhat dated.

Müller, The Origin of Metazoan Complexity: Porifera as Integrated Animals, Molecular Biology and Evolution 2003.
http://icb.oxfordjournals.org/.....act/43/1/3

You can find a signal transduction pathway diagram here:

http://en.wikipedia.org/wiki/F.....ion_v1.png

Wikipedia article here:
http://en.wikipedia.org/wiki/Signal_transduction

From what I’ve seen so far, there are a number of different complex mechanisms that contribute to contact inhibition, none of which I’ve read about so far fit evidentially into the grand claims of clumsy Darwinian synthesis, but rather fit the incredible trademarks of super-intelligent engineering, as the extensive fossil record shows a collection of fully-developed and fully-functional body plans with little to no functional failures.

It’s a mechanism, not just the phenomena. There could be other mechanisms involved, such as a programmed number of replications.

“Contact Inhibition” is the broad term used to describe an observed event, in this case the observed stop-growth of cells upon making physical contact with one another. The mechanisms behind contact inhibition are still not fully understood, and in fact may not have anything to do with contact at all. In concordance to what I emphasized earlier, more than just physical contact is necessarily required for this event to occur in any meaningful manner, which would render this to be a phenomena. for the development of complex organims and especially in the case of the human brain.

Phenomenon:
1. an observable fact or event
2. a fact or event of scientific interest susceptible to scientific description and explanation.
3.an exceptional, unusual, or abnormal person, thing, or occurrence.

Take your pick.

According to a nature review-

Now, the term contact inhibition of cell movement is used quite broadly107, 108. By contrast, it is not clear whether contact inhibition of cell proliferation depends on cell contact; in fact, there is compelling evidence that it does not109, 110. Therefore, downregulation of mitosis in confluent cells is also called ‘density-dependent inhibition of mitosis’ (Ref. 111). The contact inhibition of cell movement and proliferation is crucially important in organogenesis as well as in wound healing. Although there are several reports that cell adhesion molecules are involved in contact inhibition10, 94, 95, the mechanism for this is not fully understood.

http://www.nature.com/nrm/jour.....7_BX1.html

You continue-

As Mung suggested “is it because there is no more room in the skull,” that would indicate he was interested in mechanism.

Which you have still ultimately failed to provide to any acceptable scientific standard of explanation for reasons that I’ve just explained. It would be like asking “What makes a wheel turn?” And someone answering “Motion.”

Also, would you mind providing me with access to the articles that you’ve cited? It would be nice to find out whether they have some rich explanatory content or just another set of excessively broad, excessively hypothetical and/or excessively counter-intuitive descriptions.

PaulN: So you’ve identified the term used to explain this phenomena.

It’s a mechanism, not just the phenomena. There could be other mechanisms involved, such as a programmed number of replications.

PaulN: But you’ve still ultimately failed to get the point of the question asked by Mung.

As Mung suggested “is it because there is no more room in the skull,” that would indicate he was interested in mechanism.

PaulN: What you have not done is explain how such a marvel has evidentially arisen from Darwinian causes or even fits with the theory.

Much of your question involves the evolution of metazoan architecture which is very ancient. Differentiation of somatic and germ cells is probably a critical change. There are some clues in Porifera.

Müller, How was metazoan threshold crossed? The hypothetical Urmetazoa, Comparative Biochemistry and Physiology 2000.

Koziol, Sponges (Porifera) model systems to study the shift from immortal to senescent somatic cells: the telomerase activity in somatic cells, Mechanisms of Ageing and Development 1998.

Müller, Bauplan of Urmetazoa: Basis for Genetic Complexity of Metazoa, International Review of Cytology 2004.

A primary mechanism is contact inhibition.

So you’ve identified the term used to explain this phenomena. But you’ve still ultimately failed to get the point of the question asked by Mung. What you have not done is explain how such a marvel has evidentially arisen from Darwinian causes or even fits with the theory.

Theoretically, even with contact inhibition in place, how does it just happen to unfold to create a fully functioning complex organism? What determines when contact inhibition takes place and to what extent? How if at all, does this fit into a Darwinian scenario if the information for the limits of cell growth would have to be present ahead of time, especially when you consider how precisely every specific structure in a complex organism must fit together, interact with one another, and cooperate? The observation of contact inhibition in my opinion serves to be ultimately counter-intuitive to Darwinian claims, as the process of contact inhibition is necessarily guided and unfolds in a purposeful, precise, and specific manner.

On top of this, if you even consider the implications this has on the hypothetical development of the first complex organism/animal, then it doesn’t take long to realize that contact inhibition would be useless if it weren’t defined ahead of time by pre-existing information. In other words you could still just as easily get a multitude of organic atrocities if there are no specific parameters in place to define exactly how contact inhibition is carried out. There is nothing in Darwinian claims that necessitates the creation of a meaningful structure from the process of contact inhibition. And given this, I’d still expect to see a plethora of terribly failed body plans in the fossil record before the first successful body plans appeared. I’d expect to see amorphous, asymmetrical, incoherent collections of biomass before anything resembling what we see in the cambrian explosion came to be. Either that or I would expect for life to never have arisen at all, as contact inhibition can stop cell growth when just two cells meet one another. There’s obviously a smart mechanism behind how it selectively limits cell growth to facilitate proper function at higher levels, and dare we even conceive the hypothetical outcomes before contact inhibition was in place, and every multicellular arrangement were to grow in a cancerous fashion?

This is important in cell culture technology.

Not only is it important, but it’s logically necessary for any complex organism to exist. Also I hope I’m not the only one who sees the irony in your classifying this as technology.

Mung: Why does cell division ever stop …

A primary mechanism is contact inhibition. This is important in cell culture technology.

Your logical input always seems to come from a fresh perspective, and that’s what I’ve liked about you since you started posting here.
…
Thanks for sharing your reasoning =)

Ok, I admit it, I’m susceptible to flattery, lol. But thank you.

Have you noticed that so far you are the only one who thought my comment worthy of a response?

And here I was, thinking that it was actually relevant and important.

Zachriel:

Indeed, the human brain, with its trillions of cells, develops from a single cell.

Brains start from a single cell.

Whoop dee doo!

So does everything else in the human anatomy.

Why does cell division ever stop, and why, specifically in the case of the brain?

Is it because any more cells would become deleterious?

In the case of the brain, is it because there is no more room in the skull? Or is there some other reason that the “brain cells” stop multiplying?

ScottAndrews: Darwinism’s explanations invariably boil down to something like this:

However, if neighboring cells were to cooperate and use the resource more efficiently, then everyone benefits.

We can point to all sorts of examples of evolution in more modern times, but PaulN was concerned with the problem of selection at the cell level undermining group selection that could lead to the evolution of a cohesive cell group. Indeed, it’s a significant question.

ScottAndrews: No specifics, no mechanisms.

Let’s look at your previous statement.

ScottAndrews: If a single cell varies in some way – perhaps it can survive a slightly different temperature – then that variation can become dominant in response to environmental changes. It’s not news. That type of microevolution has been observed.

Those microevolutionary forces are exactly what are being investigated and proposed, that is, differential reproduction, selection and purification. The original transitions are very ancient (multicellularity arose more than once), but there are intermediate examples in extant nature; in particular, ATP rate and yield in bacterial microfilms. Modeling of microevolutionary forces can also help determine whether these mechanisms are sufficient to overcome the obstacle that PaulN pointed out.