Since there’s been some discussion on new body plans, here is my understanding of how they come about. Note that I am not a biologist. I’m sure someone will correct me if I am wrong. Most of this has to do with how branching processes work.
To explore how new body plans arise, we are going to travel back in time with my trusty time machine. I obviously don’t have a time machine, which is why this is only a thought experiment. As I travel back in time, I take along a passenger, whom I shall call “William”. We want to find out where the octopuses, with an obviously different body plan, arose.
We start our journey in the present, looking at a person — perhaps at William himself. Then we go back in time to look at the ancestors. Well go fast, or this would take for ever.
As we go back in time examining ancestors, we see earlier vertebrates, such as fish. We keep on going, and get to the early chordates. They had a neural bundle, but no vertebrae. We have to go further back to find the ancestors of the octopus. As we go back, we see ancestors without even a neural bundle. Eventually, we get back to the point where the ancestors of the octopus branched off.
At this point, we see two sibling organisms. One of those is an early ancestor of us, and the other is an early ancestor of the modern octopus.
I hand William a microscope, and ask him to examine both as closely as possible, and to describe the body plan that he can see in each. “What body plan” says William. “I don’t see any body plan.”
That’s where the phylum branching occurred. The body plans came later. The whole idea of “macro-evolution”, as that term is used by creationists and ID proponents, is just a complete misunderstanding.
“That’s where the phylum branching occurred. The body plans came later. The whole idea of “macro-evolution”, as that term is used by creationists and ID proponents, is just a complete misunderstanding.”
Lizzie, weren´t you saying body plans come first? Evolution can accept both? Body plans come first or later according with what we find?
You could have a simple, not very specific, body plan that specialized in two or more different ways after branching. Or you can have body plans that don’t originate until after some branching. I picked the example of vertebrate — cephalopod where the body plans probably originated after branching.
The main point, however, is that these groupings begin with early branching and then become more specialized.
Macro evolution always means the great changes required by evolution to change organs or this or that.
Body plan misses the glory of the changes needed.
Creationists understand very well evolutions branching idea.
Macro just means crossing thresholds of complexity in body parts as evolution needs to have done to explain the origins of biology.
My hernia trumps your designer.
More to the point, there hasn’t been much increase in complexity since the Cambrian. Most genes were invented by bacteria before the Cambrian.
Indeed.
I’ve made the point before that the real difficult questions of evolution lie in the gap from having a viable environment on Earth to the emergence of prokaryotes. The idea of life developing in diversity and complexity, once you have your self-sustaining self-replicators, becomes plausible. Eukaryotes from symbiogenesis, then with sexual reproduction and multi-cellularity, everything is possible. So long as you work with a do’nut and origami*.
I like Lizzie’s origami metaphor. It conveys both the possibilities and limitations of what can be achieved with the raw material of a worm and hox genes. Blas and WJM are invited to consider the superphylum Deuterostomia
*It seems a shame that the story of the Metaphyta often gets neglected in our obsession with our own deuterostome origins.
ETA: And Robert! I hate to break this to you but you are just a highly evolved worm.
There is a tendency to focus on a couple of rather arcane groups of colonial organisms. The classification of these tends to be based upon the growth patterns of their colonies, rather than their cellular fundamentals. These colonies grow large, and we are among them, as well as eating them, running away from them and training them to fetch the paper, so naturally we think that’s what biology is all ‘about’.
Those two groups divided by a common language?
I still recall my almost-disbelieving amazement, not long into my undergraduate biochemistry many years ago, at the overarching similarity across all living things at the cellular and sub-cellular level.
Alan, I like the origami metaphor too. The point is that metaphor it s not darwinism. If the origami metaphor it is what happened there is no tree, because all the junction of the tree are in the base, in the begining of multicellularity. And I agree that the fossil record fits that model, and is what Meyer in his book claims. Darwinism do not fit the fossil record of CE unless you fill the gaps with immaginary intermediates.
Agreed, we are more in the area of evo-devo
In that long (there’s a maximum window of three billion years between first life and the first evidence of multi-cellular organisms) period when prokaryotes ruled the world (maybe they still outweigh us), before sexual reproduction, horizontal gene transfer seems to have been pivotal. So yes, stretching that metaphor, the tree has tangled roots.
Then what is in dispute about the Cambrian period? You should be attacking evolutionary theory at its weakest point , where the questions are many and hard to answer. Once you are in the Cambrian all the heavy lifting is done.
Then Meyer didn`t make a mistake. Made a point against darwinism.
As you said below the CE also darwinists admits that there is no tree. If also during the CE there is no tree, there is no tree at all. Take away chordata from the phyla appeared during CE and you will find stasis. Apply the origami metaphor to the diversification of mammals and there is no tree of life. If there is no tree of life there is no darwinism.
Add to that there is no plausible scenario for OOL on earth then you have a nice hypothesis of “life seeded on earth”. If you are going to seed life in another planet you do not seed a FUCA or a LUCA, you seed as many genomas as you can trying to get the biggest quantity of survivors you can.
Let scientist forget that it would be perverse to withhold provisional assent to darwinism and you will have an alternative picture of life on earth.
Yes, let’s take a trip back in time to the universal common ancestor and follow the lineages that lead up modern-day morphological disparity.
Let’s call the morphology of the UCA “morphological set A”. It’s probably something similar to what we currently call bacteria.
As we move forward in time, we will see variations on morphological set A – diversity. Moving forward, we will find some lineages of that set stay within the overall boundaries of that set, but other lineages are being transformed in time to increasingly different morphologies. At some point, the morphology of some population down the lineage will be so different from morphological set A that we can no longer call it a member of that set; so we come up with a a new term for this now-disparate population: “morphological set B”. Now we have two distinct morphological sets (at least 2); A and B. A and B can coexist, they would just represent two different morphological sets.
But, B **had to** come from **A**, according to common descent. That means A **must have** diversified to the point of morphological disparity going forward in time. That means that a new morphological set B **must have** come from a prior species, or group of species, in set A. There’s no way around it.
Good grief, man, you’ve misinterpreted what I said. I said evolutionary pathways are very clear and in general unambiguous back to the Cambrian period but then things are more fragmentary in the Ediacaran and even more so as we look back further in time. It’s the evolution of eukaryotes from prokaryotes and prior to that, where our only real tools are the genetic morphologies and the fossil sequences that are found in extant organisms, that is more speculative. Acknowledging the importance of horizontal gene transfer is merely acknowledging relationships become tangled, not that they didn’t exist.
In your scheme – WJM’s Razor? – work from the ‘obviously different’ towards the middle by going forward from the ancestor and backward from the descendant, binning into your discrete categories as you go. Eventually you get to a parent and its offspring. At that point, an individual would have to be be in a different ‘set’ from its parents. Since ‘Darwinism’ – particularly that advanced by C. Darwin – postulates generational gradualism, how real are the ‘hard’ boundaries of your asserted sets?
The relevant sets are those of any ancestor and all its descendants. Each such set is discrete (barring HGT) and expected to be nested if simple branching and divergence are the operational parameters. Attempting to delineate sets by division along a continuum is arbitrary at the boundaries.
There is much debate and research on what the LUCA might have been.
You must either clearly define what you mean by morphology or use another word in its commonly understood biological context. I think you are confused between that and homology. The importance of understanding monophyletic groups and clades (the line of descent) is what is at issue. All species that descend from their common ancestor form a clade (with that ancestor)..
And they are called clades.
This is pure ad hominem, William. You are trying to run before you can walk. You need to put some effort into grasping the concepts you are trying to refute. The problem is yours. By the way, when was the moment when you stopped regarding other commenters as “automatons”?
How sharp or vague the boundary is, is entirely irrelevant to the point.
That they are arbitrary classifications is, again, entirely irrelevant to the point.
What ****ing point!
Try and make a clear point. How can whether a set is a monophyletic group or not be irrelevant to the topic of phylogenetics?
Does this diagram help?
Some years back someone over at the Thumb gave (in reply to some creationist crying the standard whine “IF-YOU-TELL-PEOPLE-ALL-THEY-ARE-IS-ANIMALS-THEN-THEY-WILL-ACT-LIKE-IT”) a nicely detailed explanation of why biologists classify human being as animals. He started by naming the domain Eukaryote and then describing the key defining trait of nucleated cells, proceeded all the way down thru the taxonomy and ended with what makes us homo sapiens. It was almost poetic it was so well written and I wish I had saved it because I can’t find it anymore. 🙁 🙁
Do you know what ring species are?
Geneology 101. A child is always of the same species as its parent. Always.
AHA.
Just what creationism would predict and why your first instinct was wrong.
if evolution was true then it should be, or at least a option, that at the atomic levels etc there should be great and more complexity due to easy evolutionism affecting less complex things.
Instead one finds common laws in design.
As from a designer just like his design in physics.
A common blueprint should of been the first instinct.
Darwin would of been displeased at molecular likeness.
No he wouldn’t – that is ridiculous. He’d be displeased that organisms prove to be genetically related at their very cores, and not just on gross morphology, in a hierarchic, branching pattern? Hardly something creationism would predict, but common descent – tick!
this?
I didn’t say always. Isaid since the Cambrian, a small fraction of the history of life. The liniage of proteins canbe traced and ages assigned. It works out to about two million years per protein. Hardly all at once.
This point?
So you pepper your analysis with terms of discreteness, which I point out does not work in a continuum. Whether that’s relevant to your point or not, I could not care less. You are attempting to apply a term applicable to a set of organisms at a moment in time – present diversity, which depends upon lineage extinction and reproductive isolation to create discreteness – backwards in time, where every individual still ‘exists’. Imagine trying to classify organisms according to set theory if no lineage had ever died out.
The WJM Dictionary: “Automaton” – one whose knowledge of theory prevents them from accepting WJM’s biological pronouncements without demur.
How is it that the above got posted under my name? I didn’t write it or post it.
Everything in your post here is entirely irrelevant to the point. It’s not a point about terms, classifications and definitions – it’s a conceptual point about what it physically takes to get from evolutionary point A to Z, not what you specifically call, define and classify things during or after the trip.
But then, you guys are immune to conceptual points that diverge from your ideology.
It might help if you give a specific example of “A” and “Z” then the difference between those two things can be examined in light of your claims.
It’s ironic then that you ignore so many conceptual points made against your own ideology then. Responded to Robin yet? Why not? Scared?
I wondered about that when I first saw it. It sure looks like a response to WJM, rather than WJM’s post. Either something went wrong in the software, or a moderator clicked a wrong button somewhere.
That can only be it. I guess it was just copypasta at the Thumb. I seem to remember even more detail and written with a more poetic touch but I’ll put it down to my little gray cells having passed their sell by date. Thank you very much.
Fixed it for you WJM.
You’re welcome
William J. Murray,
Irrelevant to your point but not, curiously, irrelevant to the points I was making in regard to that post. Hence my saying it.
Ah. That clears that up then. Conceptually what it takes to get from A to Z is for a lineage to suddenly – or veeeeeerrry sloooooowly – find itself in a ‘different morphological set’. Which isn’t a classification based on morphology. Or a set.
So this conceptual point (not set theory and not a point re: classification) is … what? After a lot of change things can become quite different? Thanks for that. No wonder you tend to steer clear of the sciencey discussions.
But then, you guys are immune to conceptual points that diverge from your ideology.
Kapow! [I’ll tell the evolutionists they’re ideologically blinkered again. That always winds ’em up!]
The serious point I was trying to get across is the distinction between a ‘contemporary’ view of organism differences and a historical one. WJM repeatedly uses terms such as ‘disparity’ and ‘divergence’ to relate to the difference between an ancestor and a descendant. And to use a concept one might dub ‘chronophyla’ interchangeably with the phyla distinguishing broad groupings of extant forms. This leads him to err in his assessment of what we should see – continuous production of ‘new phyla’.
One does not diverge from an ancestor, but from other descendants of it. The future disparity between descendant members of a clade is not a disparity between any member and the original ancestor.
Simply thinking of tree growth ought to make the point clear – a single limb does not diverge; branched pairs do – but it obviously doesn’t, as WJM regards all such considerations as ‘irrelevant’. To return to my “Y”, if time goes up the screen, the divergence is between the arms. Depending on the amount of change encompassed, the arms may represent any taxonomic class. But this does not mean that the same taxonomic distance has been traversed in going from the base to one of the tips – even though (all else being equal) they are the same genetic distance apart as the two arm-tips.
There’s always the Douglas Axe approach: calculate the distance between tips to prove they can’t be related.
I agree, you’re no biologist. How do you know they are “siblings”? How do you know that’s where the “branching” occurred? How do you know which is the ancestor of “us” and which is the ancestor of “them”? You don’t.
How do you know? The two siblings did or did not not share the same body plan? They did? So obviously the difference in body plan came later, by definition. The common ancestors had the same body plan, therefore one of them evolved a different body plan later. QED.
A complete misunderstanding of what?
How do non-IDists and non-Creationists use the term?
Neil Rickert:
So disparity precedes diversity? Isn’t that what Meyer argues, and isn’t that what Lizzie disagrees with?
Meyer claimed that the evidence was contrary to what evolutionary theory predicts. Lizzie, instead, says that the evidence is precisely what the theory predicts.
Just so we’re absolutely clear. She said this in her OP?
Neil, are you even sure that you’ve actually proposed a thought experiment?
You know the answer to this, Mung. At least, it has been repeatedly given in threads in which you have been an active participant. Microevolution – evolution within a single gene pool. Macroevolution – evolution taking place at levels above single gene pools.
Of course not. The original organisms to which each phylum owes its independent ancestry are siblings. Under common ancestry, this must be true – they converge upon their common ancestor: their parent. You may disbelieve common ancestry, but disparity is not observed in any siblings today, nor is it necessary to invoke it at ‘phylum founding’ nodes, so you may have misread what Neil said.
Siblings are certainly not ‘disparate’, nor particularly diverse.
Me
Of course, only full siblings if asexual – collections of genes from conspecifics if not, with a more complex, but still coalescent, set of ‘origins’.
Mung: So disparity precedes diversity?
Allen: Of course not.
So Elizabeth is wrong, or has misread Meyer.
Neil Rickert:
How so?
Allen makes it clear (I think) that the theory predicts that diversity precedes disparity. And isn’t that exactly the same argument Meyer makes?
IOW, to get back to the OP, before we can expect to see a new “body plan” there should be much diversity, so much so, that after sufficient time, two species which share a common ancestor are now classified in two completely different and distinct phyla.
Mung,
Yes, if by ‘two species’, you are referring to two descendants far removed in time from the last common ancestor. No, if you mean two species immediately descended from the last common ancestor.
From the OP:
So this hypothetical ancestor of humans and octopuses had no body plan?
Is that part of the thought experiment?
Why not?