On May 20, 7:47�am, someone <
glenn.spi...@googlemail.com> wrote:
> On Monday, 20 May 2013 12:25:31 UTC+1, Ron O �wrote:
> > On May 20, 5:38 am, someone wrote:
>
> > > I took a look on thehttp://
www.talkorigins.org/website'sFAQ page
>
> > > and looked for the answers to the following questions but couldn't find
>
> > > them there. They concern the atheist evolutionists (those that rule out
>
> > > mutation by design) were suggesting the evolutionary pathway was from unicellular lifeforms to multicellular lifeforms.
>
> > It isn't so much as ruling something out, but just not having any
>
> > reason to rule it in. �You don't have to be an atheist to understand
>
> > the usefulness of not having to consider more complexity when there is
>
> > no reason to consider it.
>
> I assume you think that is a fair assessment of the situation. Would you have
> considered it fair for a theist to have stated that it wasn't so much a case of
> ruling out random evolution, but one of just not having any reason to rule it in?
The theist would be wrong. What evidence do you have that anything
exists to do the directed evolution? You have matter and energy. No
one has found a chemical reaction in life that is thermodynamically
impossible. You have lifeforms replicating imperfectly, and you can
measure evolution in populations.
>
> (determined evolution would replace random evolution, not be an addition)
It would be an addition. Evolution is happening, and you don't have
any evidence that it is directed.
> > > I was wondering why a
>
> > > unicellular lifeform if it was to become multicellular wouldn't just
>
> > > become a multicellular string of similar cells or some other basic
>
> > > replicable structure, or was that a step in the theory, or was there
>
> > > something else they might be expected to become?
>
> > If you study biology you will soon learn that there is a grand
>
> > diversity of lifeforms that cover the whole spectrum of what you are
>
> > thinking of. �There are single cells, single identical cells in
>
> > strings, biofilms of a layer of single cells, organized
>
> > conglomerations of cells like sponges that can reassemble if you
>
> > reduce them to single cells and then let them get back together. �In
>
> > short there are intermediate stages and they still exist and happily
>
> > reproduce in nature. �These intermediate stages aren't trying to be
>
> > anything else. �They just survive and reproduce and some of them, by
>
> > chance, started to make strings of cells, some started to make layers
>
> > and then 3D structures etc. �These intermediates could obviously
>
> > survive because similar lifeforms still exist.
>
> So am I right in thinking that at one stage they are thinking that at
> some stage our life form ancestor was *possibly* a sponge-type collection
> of cells, in which each cell of which was responsible its own reproduction?
That is what the data indicates. Our lineage nests within sponges,
and we are most closely related to a particular branch of sponges.
>
> Presumably this would be a collection of cells in which mutations in one cell
> wouldn't necessarily become more prevalent in the population than when they
> occurred.
In various sponges evolution can be asexual or sexual. They are
primative enough so that somatic mutations can take over a portion of
the sponge that produces another sponge. It is like somatic mutations
in a tree branch where the seeds produced by that branch transfer
their mutation to the next generation. In a sense this happens in
you, but your arm can't produce the next generation without some
assistance. The mutations have to occur in the germ line to be
transmitted to the next generation in humans. Every cell division new
mutations happen, and it takes a few cell divisions to produce your
gonads from the single cell created by the fusion of the sperm and
egg.
In the case of a tree branch the somatic mutation could be selected
for (the branch might have better resistance to pathogens or insects),
but in humans you usually have to wait for expression in the progeny.
The branch might be healthier, grow better and produce more seeds than
the other branches of the tree. You can observe this in some
variegated shrubs where the plant that produces yellow and green
leaves will put out a branch that produces only all green leaves. A
lot of times the all green branch does better than its peers in terms
of biomass production.
>
> > > Also should such a basic structure be thought of as one organism, or a
>
> > > collection of organisms? If one organism, then what if the cells behaved
>
> > > roughly the same but didn't stick to each other but floated apart?
>
> > That is the thing about evolution, you get into categories that are
>
> > intermediate and no hard and fast rule applies. �For strings of cells
>
> > you can break the string and get two strings that continue to
>
> > reproduce. �You can parcel up biofilms anyway that you want down to
>
> > single cells and they will reproduce. �You can take a sponge and
>
> > divide it up into single cells and you can create a bunch of little
>
> > sponges as the cells reassemble. �So these primative types of
>
> > multicellular organisms are both types. �We can't do that with
>
> > multicellular organisms like yourself, so as you get more complex
>
> > multicellular types it gets easier to say that a bunch of cells make
>
> > one organism instead of being just a bunch of cells.
>
> Why can't a sponge just thought of as a collection of reproducing cells
> that stick together in forms? Because if it can then why make it more
> complex and say that additionally you need to be able to understand it
> as being a single organism?
Is a sponge a single organism or colony of cells? With some sponges
it is hard to make the distinction. That is what evolution would
produce. We do not make sponges more or less like colonies. We can
categorize, but we are just observing what already exists. Obviously
each step was able to survive and many do so today.
>
> Could there be quite a genetic diversity within one sponge
> if cells from one sponge joined with the cells of a distantly related
> sponge, and then with another distantly related sponge, etc., or is there
> some mechanism to prevent this?
Every cell division you have new mutations. You can't keep them from
happening. Identical twins are not identical genetically. The cells
in your body are not identical genetically. It is just that most
mutations do not do much that we can observe. Some do bad things like
cancer that we can observe. If part of your liver was better at some
enzymatic function than the original single celled zygote how would
you tell? The mutations that matter in terms of evolution are the
ones that occur in the germ line.
>
> > > Also how is it envisaged that the majority in a collection of self replicating
>
> > > cells will sacrifice reproduction and instead it be delegated to a minority
>
> > > of the cells to pass on their genetic code (which will encode for future organisms)?
>
> > The thing about evolution is that a lifeform only has to work and
>
> > reproduce competitively. �The lifeforms that were not competitive are
>
> > gone. �We only see the winners. �So we can see a progression of
>
> > multicellular types to those where most cells sacrifice their own
>
> > reproductive ability for the greater good. �It just worked, and you
>
> > probably can't draw a line where any cell had to make that decision.
>
> > In Cnidaria you can chop up a hydra and it will regenerate whole
>
> > organisms, but more complex relatives like jellyfish can't be chopped
>
> > up. �When did the cells in a hydra like organism evolve to a point
>
> > where you can't take a part and make a whole? �It was obviously so
>
> > gradual that it just happened. �Hydra have tenticles to snag prey and
>
> > a mouth opening and sort of a gut, so where do you draw the line.
>
> > Evolution is like that. �You expect to have gray areas where things
>
> > are half and half.
>
> So what is the progression you see from a collection of self replicating cells which all individually reproduce to one in which the majority will sacrifice
> reproduction and instead it be delegated to a minority of the cells to pass on their genetic code (which will encode for future organisms)?
>
> Are there sponges where a tenth of the cells don't replicate any more?
I don't know.
>
> What is the random evolutionary explanation of it?
It happened because it could and the organism could survive and
compete in the biosphere. Essentially if it were impossible or
nonviable we would not observe the intermediates that we have or the
final products of billions of years of evolution. If you are talking
about a step by step explanation we are still working on it. We can
see some probable intermediates because they still exist. Extinction
has left some gaps. Like I said all we observe today are the
survivors.
You might be hung up on progression. There are still single celled
organisms that reproduce asexually and single celled organisms account
for the bulk of the biomass and number of cells in the biosphere. You
have more bacteria in you and on you than cells in your body. If
humans were created for a purpose it looks like we were created as
condominiums for other organisms. It isn't so much of a progression
as what has survived to reproduce.
SNIP:
Ron Okimoto