Evolution question - How did mammals originate ?

Originally posted by KellyJay
I fail to see why it is an unreasonable request. I'm not asking for
much in my opinion... small obstacles...something that must happen
all the time considering the variety of life on the planet

IMHO, you are asking for "much". If you consider "the variety of life on the planet" it is by no means something that "must happen all the time", at least not in an obviously identifiable sense. Let's take a quick look at some numbers.

I'm going to use "mainstream" numbers, at least to an order of magnitude or so. If you want to object that all the variety of life happened at a single time, when God created them all 6,000 (or so) years ago, you can do so, but your claim that you are "not asking for much" is evidently predicated on what scientists are claiming rather than on your assumption that evolution doesn't happen, in which case you would clearly be asking for much.

Since you are concerned with multicellular life, I'll stick to that. There are somewhere between 3 and 10 million species of multicellular (plant and animal) life on the planet, a seemingly huge amount of diversity. Consider, though that these species are divided among about 20 animal phyla and (I'm less sure here) a similar number of plant phyla. A phylum corresponds more or less to a "basic body plan". Thus the phylum chordata corresponds to all animals with a notochord, a "spinal cord" or the like. The vertebrates, including us, are chordates. Each of these 30-50 phyla has been evolving separately for essentially all of the past 600 million or so years. It is possible that there have been a few splits in that time where some of the existing phyla are the "sister groups" to other phyla, but most of the current phyla can be traced back more than 500 million years. (Again, assuming mainstream numbers. If you want to claim that the mainstream numbers are wrong, this is not the place to do it as this discussion, and your claim, is based on those numbers.)

As I pointed out in another post, the whole notion of "limbs and organs" appears to have evolved once -- back when differentiated-cell life evolved from single-celled life. That is, the probabiliites of a single-celled life form evolving into a multicelled life form seem quite low. It hasn't happened often and as far as we can tell, the only time it did happen was after more than 2,000 million years of life. Expecting it to happen in a small sample as we are observing that sample in a laboratory is definitely "asking for much".

Now how about new "limbs and organs" in multicellular life? That obviously has happened a lot more frequently. Again, though, you have to take each lineage separately to estimate that frequency. Within our own lineage, we can certainly see development of organs like eyes and lungs or the tetrapod limb arrangement among the innovations that have evolved in our phylum. So how frequently does that happen? I'm not an anatomist, but, for the sake of argument, let's say that our bodies contain about 200 recognizable "limbs and organs." (That's not too far off.) Let's tentatively make the (IMHO dubious) assumption that these have appeared at a uniform rate. That would be 200 "limbs and organs" divided into 600 million years or 1 per 3 million years. Now with these (optimistic) numbers and, let's say, 3 million species, that ought to mean one novel limb or organ per year worldwide across all lineages. I'm not so sure that you would recognize a novel organ among, say, snails, but under the assumption of 1 per year, you'd need to be looking for them. Personally, I am a lot more familiar with vertebrate body plans than molluscan, although I have no doubt that evolution proceeds among molluscs at a comparable rate. You just can't demand to see it develop in the same directions among different phyla.

Unfortunately for these numbers, the rate of appearance for novel body parts is probably nowhere near uniform. The more basic the structure, the more deeply imbedded in the genome it is and the less likely it is to be readily modifiable. So we have not seen truly "novel" organs appearing among macroscopic animals in recent times. In fact, even the ones we can identify as having "presumably" developed as novelties were probably not identifiable as novelties for a good long time. For example, milk producing glands, one of the defining characteristics of the mammals (to revert to the ostensible topic of this thread) appear to have developed from something like sweat glands. The development from sweat glands that secreted a fluid that functioned to eliminate waste products and/or as a cooling mechanism to similar gland that produced a more nutritious fluid, to a similar gland that concentrated that production and directed it to a nipple would have been an extended development and at any given point in the change, the developing organ would not have appeared "novel". Taking into account only the last few tens or even hundreds of years, the changes would appear to be "minor" and involve pre-existing structures. It is only from the perspective of a few million years that we can look back and say that a novel organ has appeared. On that sort of time scale, a rate of a "novel" organ every few million years is probably not unreasonable and could be called "all the time" but on the time scales involved in laboratory experiments or even human scientific observations of wild critters, expecting to see new organs is a rather large expectation.

Best Regards,
Paul

Originally posted by prn
IMHO, you are asking for "much". If you consider "the variety of life on the planet" it is by no means something that "must happen all the time", at least not in an obviously identifiable sense. Let's take a quick look at some numbers.
...[text shortened]... new organs is a rather large expectation.

Best Regards,
Paul

The claim that there were simple forms of life (simple being relative)
and we have what we see today, new limbs, organs, systems would
have been springing into existence for millions or billions of years.
The mechanics of the process would have to be ongoing, so all along
the evolutionary time line we should be seeing this taking place.
Unless you want to add stop and starts for evolutionary mutations.
Without this evidence or I should say without seeing this process
actually doing that; what is being asked is that a process that has
never been witnessed to that degree, do some thing that has never
been seen to that extent mutate the simpler life into all the variety
there is today in life.

If I’m not mistaken I was asked why I did not believe evolution
because of my small experience in design. Seeing the effort and
planning required into making functionally complex systems work, I
don’t see it happening without a plan, a purpose, and a design. So
adding a limb or organ that wasn’t there before requires all the
various connections of nerves, muscles, blood flow and so on, it
requires that the rest of the body’s resources not be robbed while an
additional limb is formed.

I believe that God created all life at one time as described in scripture,
and I also without hesitating say it is faith as far as I’m concern. Just
as I’m telling you anyone who says that evolution took simple life
forms and transformed life into the complexity, the variety, and the
vast array of life we see today over time is doing so in faith.

”… but your claim that you are "not asking for much" is evidently
predicated on what scientists are claiming rather than on your
assumption that evolution doesn't happen, in which case you would
clearly be asking for much.

I believe in the term evolution, but it is how the word is used. Like I
have said we can use the term to describe how cars have evolved over
time, how bridges have evolved over time and so on. That is different
than saying that we can move from a simpler life form on say the
cellular level, into one that has a variety of organs, one that must
reproduce with another sex, one that must feed it’s young by organs
that fulfill the necessary requirements for it’s young.

As I pointed out in another post, the whole notion of "limbs and
organs" appears to have evolved once -- back when differentiated-cell
life evolved from single-celled life. That is, the probabiliites of a
single-celled life form evolving into a multicelled life form seem quite
low. It hasn't happened often and as far as we can tell, the only time
it did happen was after more than 2,000 million years of life.
expecting it to happen in a small sample as we are observing that
sample in a laboratory is definitely "asking for much".

Appeared once? Why would that be? The process is an ongoing one
correct, it does not have stop and start dates programmed into the
mechanics of the process. If we cannot see it, we have no way of
knowing if it has happened, even if it happens right in front of us, we
know it happens, we know it did happen because? I believe the word
we should use is faith!
Kelly

Originally posted by KellyJay
Appeared once? Why would that be? The process is an ongoing one
correct, it does not have stop and start dates programmed into the
mechanics of the process.

I did not say that "limbs and organs" appeared once. I said that the "notion" of limbs and organs appeared once. That is, as far as anyone can tell, multicellular life, with the "notion" of different cells specializing in particular functions evolved only once from a single-celled ancestor. What I am saying is that BECAUSE we who do accept the evolutionary explanation have concluded that evolution from a single-celled ancestor to a multicellular descendent with specialized "limbs or organs" has happened only once in the entire history of life on earth, you cannot claim that according to OUR theories this should be a common occurrence.

OTOH, although we (who accept the evolutionary explanation) do accept a higher frequency of "new" "limbs and organs" developing within a multicellular lineage, the evolutionary explanation of biodiversity does NOT claim that these developments take place instantaneously or even recognizably within the time span of a human life. All known occurences of such have involved exaptation of existing "limbs or organs" (or at least some kind of specialized cells). The point where we can reasonably conclude that a novel structure has developed is likely to be significantly later than the starting time. We cannot typically find a "novel" structure within a small number of generations since each successive generation displays only a small change to a structure that existed in the preceding generation.

If we cannot see it, we have no way of knowing if it has happened, even if it happens right in front of us, we know it happens, we know it did happen because? I believe the word we should use is faith!

As you have stated many times, you seem to believe that "faith" is the only alternative to "certainty". The rest of us have accepted that there can be varying levels of "support" for an idea.

Best Regards,
Paul

Originally posted by prn
I did not say that "limbs and organs" appeared once. I said that the "notion" of limbs and organs appeared once. That is, as far as anyone can tell, multicellular life, with the "notion" of different cells specializing in particular funct ...[text shortened]... arying levels of "support" for an idea.

Best Regards,
Paul

What I am saying is that [b]BECAUSE we who do accept the evolutionary explanation have concluded that evolution from a single-celled ancestor to a multicellular descendent with specialized "limbs or organs" has happened only once in the entire history of life on earth, you cannot claim that according to OUR theories this should be a common occurrence.[/b]

So if I understand you, and I am not sure I do...

1. You who accept/believe in evolution think that 'limbs or organs'
have happened only once in the entire history of life on earth.
Reasons we know this are?

2. I cannot say that the mechanism that had cellular level changes
because of mutations in DNA would continue as it always has from
the beginning. I should say that we believe how it behaved in the
beginning instead, so you believe it has stopped doing what it used
to do in the past. Reasons we know this is because?

3. Both 1 and 2 have never been seen, recorded, or duplicated
in the wild or lab, yet you know/believe it is true and it isn't faith
on your part? Reasons for that is why? If the mechanisms of
evolution are so slow we cannot see it, why would you think it did
one thing in the past and another in the present? We still have
cellular level life today, and I guess all points in-between, why
would the process not do what it was supposedly doing in the past?


As you have stated many times, you seem to believe that "faith" is the only alternative to "certainty". The rest of us have accepted that there can be varying levels of "support" for an idea.

Yes, I agree with that. I would call those support levels faith or belief.
It certainly isn't much of anything else. We can argue on the syntax,
but I believe that to be true.
Kelly

Originally posted by KellyJay
So if I understand you, and I am not sure I do...

1. You who accept/believe in evolution think that 'limbs or organs'
have happened only once in the entire history of life on earth.
Reasons we know this are?

The main reason we accept this hypothesis has to do with the DNA structure of multicellular life contrasted with that of unicellular life. I do not have the data at my fingertips, but as I understand it, there are DNA markers present in all multicellular life indicating a common origin.

2. I cannot say that the mechanism that had cellular level changes
because of mutations in DNA would continue as it always has from
the beginning. I should say that we believe how it behaved in the
beginning instead, so you believe it has stopped doing what it used
to do in the past. Reasons we know this is because?

I have NEVER suggested that anything has stopped doing what it did in the past. What I have said is that the changes that would be necessary to get from unicellular to multicellular appear to be difficult and therefore rare. If something is unlikely enough, then we cannot expect to see it happen just because we stick our nose into the soup. I have observed that the only "known" occasion of a change from unicellular to multicellular appeared to have taken approximately 2.5*10^9 years from the time life appears to have begun. This is not indicative of something we should expect to see happen in a laboratory. I have no reason to believe that the processes that caused this to happen the first (and AFAICT only) time have ceased to operate, but I also have no particular reason to believe that it is something that happens at all often either.

To digress for a moment, it is possible that such unicellular to multicellular mutations have occured one or more times during the past 500,000,000 years but that the presence of multicellular life filling the niche has prevented the results of such mutations from becoming established. We cannot tell from available evidence if this has or has not happened. We can guesstimate from the fact that unicellular life forms were present for approximately 2,500,000,000 years before multicelluar life that it doesn't happen often.

3. Both 1 and 2 have never been seen, recorded, or duplicated
in the wild or lab, yet you know/believe it is true and it isn't faith
on your part? Reasons for that is why? If the mechanisms of
evolution are so slow we cannot see it, why would you think it did
one thing in the past and another in the present? We still have
cellular level life today, and I guess all points in-between, why
would the process not do what it was supposedly doing in the past?

I can't tell what you are referring to as "both 1 and 2". We have seen evidence of a long period of unicellular life followed by a shorter (but still VERY long by human standards) period with both unicellular and multicellular life. We have LOTS of evidence that "cellular level changes because of mutations in DNA" happen continuously. We have LOTS of evidence of that both in the lab and in the wild. I have no clue what you are talking about here. I have no reason to suspect that any process is failing to do today "what it was supposedly doing in the past." The only point I have brought up against your expectations that you are "not asking for much" is the point about frequency.

Suppose you were observing the US political process during August of 2003. Would it be reasonable to complain that we had stopped holding elections? Of course not. The frequency of elections in the USA is not such that observation during a random month is guaranteed to have an election to observe. If we compare the time that we have actually been systematically looking for speciation events (much less higher level changes) to the election cycle, it is more nearly comparable to looking for an election for a random minute and complaining that we have not seen an election being held so the political process has "obviously" broken down.

Let's consider the numbers once again. Let's suppose (contrary to fact) that we have actually been looking continuously for any such events for the entire 145 years since the publication in 1859 of Darwin's On the Origin of Species by Means of Natural Selection. Compare that to the time since evidence suggests that multicellular life arose from unicellular life: approximately 600 million years. The 145 years is approximately 1/4,000,000 of the time since the only occasion we know of. Consider now the event cycle of US Presidential elections: 4 years. There are a bit over 126 million seconds in 4 years so a fraction comparable to 145 years would be just under 32 seconds. How reasonable is it to observe the US political process for 32 seconds and complain because you have not seen a presidential election? A random minute is quite generous.

I wish to reiterate that you have been saying that according to OUR theories you should expect to see changes at the level you are asking for. On the contrary, according to OUR theories what you are asking for is equivalent to demanding to see an entire US presidential cycle in any random 32 seconds. It is only because the biblical literalist believes that the entire history of the earth has taken place within or nearly within historical times that 145 years seems like a long time.

Posted by prn: As you have stated many times, you seem to believe that "faith" is the only alternative to "certainty". The rest of us have accepted that there can be varying levels of "support" for an idea.

Posted by KellyJay: Yes, I agree with that. I would call those support levels faith or belief. It certainly isn't much of anything else. We can argue on the syntax, but I believe that to be true.

Your use of the word "faith" appears to be quite non-standard. I know you've been arguing with Bennett about this, but most people do not use the word "faith" the same way you appear to. In matters scientific, we don't normally talk about "faith" but about "confidence levels," "error bars" and such. The most crucial difference is that science attempts to quantify the degree of support that we are considering. If you confuse that with the term "faith" then we lose all that quantification. The difference is a good deal more than a difference in "syntax" (or "semantics" which would be a better term).

Best Regards,
Paul

Originally posted by prn
The main reason we accept this hypothesis has to do with the DNA structure of multicellular life contrasted with that of unicellular life. I do not have the data at my fingertips, but as I understand it, there are DNA markers present in all multicellular life indicating a common origin.

[b]2. I cannot say that the mechanism that had cellular level changes
be ...[text shortened]... fference in "syntax" (or "semantics" which would be a better term).

Best Regards,
Paul

If you confuse that with the term "faith" then we lose all that quantification. The difference is a good deal more than a difference in "syntax" (or "semantics" which would be a better term).

[/b]Quite right "semantics", I guess I have been spending to
much time in UNIX.[/b]

[/b]I'm going to have to come back to this later.
Kelly[/b]

Originally posted by Acolyte
<Acolyte tuts> Comments like this give the Wolfpack a bad name. 😉

Yea, but it is interesting. 😀😛