Clues To Ancestral Origin Of Placenta Emerge In Genetics Study

Remind me again, how does ID explain the origin/evolution of the placenta?

Charlemage: There is nothing in that paper that proves the religion of evolutionism. If human placentas evolve from egg shell linings in birds by random chance, then why don't human placentas evolve every time you fry an egg? You add energy to the chicken egg, so why doesn't the evolution happen every day at the breakfast table?!

PvM: Bye Bye troll

Charlemage: There is nothing in that paper that proves the religion of evolutionism. If human placentas evolve from egg shell linings in birds by random chance, then why don't human placentas evolve every time you fry an egg? You add energy to the chicken egg, so why doesn't the evolution happen every day at the breakfast table?!

Charlemage logic matches up with www.youtube.com/watch?v=FZFG5PKw504

The invention of the placenta facilitated the evolution of mammals

PvM: Bye Bye troll

Charlemage: There is nothing in that paper that proves the religion of evolutionism. If human placentas evolve from egg shell linings in birds by random chance, then why don't human placentas evolve every time you fry an egg? You add energy to the chicken egg, so why doesn't the evolution happen every day at the breakfast table?!

So, these same mechanisms, (gene duplication followed by divergence and then elaboration of regulatory functions and developmental pathways), hve been responsible for many novel evolutionary features, including hemoglobin, feathers, placentas, etc. The mechanisms of gene duplication are well understood and the mechanisms of divergence are well understood. We are also beginning to understand the mechnisms that allow for the evolution of gene regulation and changes in developmental pathways as well. Once again, Darwin's dangerous idea has been dramatically confirmed. Seems that the God of the gaps just keeps getting smaller and smaller.

Perhaps it would be better to embrace the science rather than whine about the supposed "moral implications". Otherwise, when the science becomes so overwhelming and undeniable, people might just remember the moral behavior of those who tried to deny the science and forget that science still can't make any moral decisions for you.

David Stanton: Perhaps it would be better to embrace the science rather than whine about the supposed "moral implications". Otherwise, when the science becomes so overwhelming and undeniable, people might just remember the moral behavior of those who tried to deny the science and forget that science still can't make any moral decisions for you.

Article Evolution and morphogenesis of the placenta in sharks William C. Hamlett Department of Anatomy, Medical College of Ohio, Toledo, Ohio 43699 Abstract Placental sharks sequentially utilize three modes of embryonic/fetal nutrition to nourish their developing young - viz., vitellogenesis, histotroph secretion, and hematrophic placentation. These are the principal modes employed by vertebrates in general. The progressive shift from reliance on yolk, to histotroph, then to the placenta mirrors the probable stages in the evolution of placentation in sharks. Preimplantation shark embryos begin their ontogenetic development by reliance on yolk. In vitellogenesis, energy-rich precursors of hepatic origin are stored in oocytes prior to ovulation. Following fertilization, embryogenesis and fetal development proceed at the expense of the yolk stores sequestered in the yolk sac. Yolk is made available to the developing young by two means. Yolk is partially solubilized in the yolk syncytium of the yolk sac and subsequently modulated through the yolk sac endoderm. Yolk metabolites are then transported across the vitelline endothelium to reach the fetal circulation. Yolk granules are physically transported to the fetal gut by ciliated cells lining the ductus vitellointestinalis. The ductus is an endodermally lined conduit that extends from the yolk sac to connect to the fetal gut where digestion and absorption occur. Following depletion of the yolk stores and prior to development of the placenta, nutrient substances may be supplied to the fetus by secretory activity of the uterus in the form of histotroph. Histotroph may then be ingested and/or absorbed. In the transition from the yolk-reliant and histotrophic phases to a placental situation, there is a coincident shift in the function of the maternal uterus to one of a nutrient-producing or -transporting organ. Essential adaptations of the uterus include: enhanced secretory function, expansion to accommodate the embryos, respiration, osmoregulation, waste disposal, and protection of the young. As the yolk sac differentiates into a placenta, focal areas of the uterus become modified as uterine attachment sites. It is at the utero-placental complex that nutrient and metabolic exchange between mother and fetus will be effected. Paraplacental uterine sites may also continue to play a role in the elaboration of histotroph. The placenta is specialized into two segments: a proximal, smooth portion that has characteristics of a steroid-producing tissue and a more richly vascularized distal portion that is a nutrient-transporting tissue. Evolution of placentation involves modifications of existing maternal and fetal membranes. The ontogenetic transformation of the shark oviduct into a functional uterus for the retention and metabolic support of developing young certainly is modulated by endocrine regulation. In the developing fetus, the yolk sac and stalk display terminal differentiation into a regionally specialized placenta and an umbilical cord respectively. Accessory vascular structures of the umbilical cord, termed appendiculae, are present in some species.

The evolution of complex organs is a source of controversy because they require the contributions of many adaptations to function properly. We argue that placentas are complex, that they have evolved multiple times in Poeciliopsis, and that there are closely related sister taxa that have either no placentas or intermediate stages in the evolution of a placenta. Furthermore, placentas can evolve in 750,000 years or less, on the same time scale as suggested for by theoretical calculations for the evolution of complex eyes. Independent origins of such complexity, accompanied by sister taxa that either lack or have intermediate stages in the evolution of the trait, present an opportunity to study the evolution of novelty and complexity from a comparative, evolutionary perspective.

Now that we live in pretty good shelters that keep wild animals away from our young ... can we go back to laying eggs please? :-)

Stacy S.: Now that we live in pretty good shelters that keep wild animals away from our young ... can we go back to laying eggs please? :-)

Eric Finn:

Stacy S.: Now that we live in pretty good shelters that keep wild animals away from our young ... can we go back to laying eggs please? :-)

I do understand your wish that is shared by many females. Please, allow some nitpicking. What do you mean by "wild animals", as compared to ... what? Regards Eric

Stanton:

Eric Finn: Please, allow some nitpicking. What do you mean by "wild animals", as compared to ... what?

As in actual predatory animals, such as large eagles, wolves, jackals, lions, tigers, and bears that would seize and feed upon the young of other animals, including those of humans.

Eric Finn: Stanton, do you think that wolves are "wilder" than rabbits?

Stanton:

Eric Finn: Stanton, do you think that wolves are "wilder" than rabbits?

Tell me, moron, which is more likely to attack and eat an unguarded five-year old child, a wolf, or a rabbit?

Depends on the rabbit:

http://www.youtube.com/watch?v=XcxKIJTb3Hg

Perhaps a little levity will ease the tension...

As a parent of an egg, I wouldn't be concerned about a bunny eating my offspring. True. Unless it were the Evil Easter Bunny.

Not the first time someone has wished that humans were egg layers rather than viviparous. This thought frequently occurs in maternity wards.

There was some talk of developing an artificial womb a while ago. With advances in artificial organs and reconstructive medicine, it might be possible someday. The tissues of the placenta and the membranes are derived from the embryo, not the mother, parts of the ancient shelled egg exaptated.

My idea was to reengineer walking wombs such as cows to support human development. Embryos can sometimes be transferred between related species with successful development.

Eric Finn:

Stanton:

Eric Finn: Stanton, do you think that wolves are "wilder" than rabbits?

Tell me, moron, which is more likely to attack and eat an unguarded five-year old child, a wolf, or a rabbit?

I do not know the reason you are attacking every post I make, apart from me being a moron. Panda's thumb has been a great asset for me, not only by providing information, but also providing me an opportunity to discuss items that puzzle me. Stanton, if your aim is to stop me posting on this site, you are very close to achieving that goal. Regards Eric

Depends on the rabbit:

From the article:

They found that the placenta develops in two distinct stages. In the first stage, which runs from the beginning of pregnancy through mid-gestation, the placental cells primarily activate genes that mammals have in common with birds and reptiles. This suggests that the placenta initially evolved through repurposing genes the early mammals inherited from their immediate ancestors when they arose more than 120 million years ago.
In the second stage, cells of the mammalian placenta switch to a new wave of species-specific genes. Mice activate newly evolved mouse genes and humans activate human genes.

For those of you interested in thinking logically, let's break this down. There are two types of ideas in this paragraph: facts, and "suggestions." The facts are that all most of the genes activated during the first stage are common to mammals, birds, and reptiles; and during the second half, mice activate genes unique to mice, and humans activate genes unique to humans.

This is science, and absolutely fascinating.

The "suggestion" is that because similar genes common to several species are activated during the first stage, they are "ancient" genes.

This is not science. It's speculation, premised on the assumption of common descent, and with absolutely no evidence, novel or otherwise, to support it.

By analogy, a hybrid vehicle and a model T both have tires made of rubber (something in common), and things not in common (the unique design of their engine). The inference to evolution is like saying, "Well, because we know that hybrids and model T's are related, we can conclude that tires are ancient and inherited by both."

That's an absurd inference.

The real challenge here is to understand how those genes came to work together in coordination -- is there a feasible stepwise pattern from "no placenta" to "protoplacenta" to "mammalian placenta?"

Not yet. Quite the contrary, it looks like there's a sudden switch from universal genes (all of which are still inexplicably coordinated) to species-species genes (all of which are also still inexplicably coordinated). Like noticing that certain elements of different computer models are shared, and certain elements are radically, uniquely, different in a highly coordinated manner.

That inference is also not science. It's an inference. It's the design inference. But it's just as reasonable, if not superior, to the alternative.

The problem with evolutionists is they take perfectly good science, and make ridiculous, unfounded proclamations of "yet more evidence than evolution." The problem's not in the science. The problem's in your interpretation thereof.

ungtss,

Your argument presupposes that every piece of evidence has to support the whole theory all over again. There's at least a couple of problems with that approach.

1) An already established theory is supported by the totality of the relevant evidence, not any one piece thereof.

2) Once the general principles of a theory are established as being well supported by the evidence, it is quite reasonable to regard those principles as being well supported by the evidence.

Henry

By analogy, a hybrid vehicle and a model T both have tires made of rubber (something in common), and things not in common (the unique design of their engine). The inference to evolution is like saying, “Well, because we know that hybrids and model T’s are related, we can conclude that tires are ancient and inherited by both.”

ungtss: From the article: By analogy, a hybrid vehicle and a model T both have tires made of rubber (something in common), and things not in common (the unique design of their engine). The inference to evolution is like saying, "Well, because we know that hybrids and model T's are related, we can conclude that tires are ancient and inherited by both." That's an absurd inference.

"...tires are ancient and inherited by both."

Henry J: ungtss, Your argument presupposes that every piece of evidence has to support the whole theory all over again. There's at least a couple of problems with that approach. 1) An already established theory is supported by the totality of the relevant evidence, not any one piece thereof. 2) Once the general principles of a theory are established as being well supported by the evidence, it is quite reasonable to regard those principles as being well supported by the evidence. Henry

Shebardigan: Any two wheeled vehicles may be shown to be derived from a common ancestor; the material used for the wheel-to-road interface ("tyre") is a contingent detail.

So, yes,

"...tires are ancient and inherited by both."

Any two wheeled vehicles may be shown to be derived from a common ancestor; the material used for the wheel-to-road interface (“tyre”) is a contingent detail.

Faulty, obviously. Paradigm-dependent.

Shebardigan:

ungtss: From the article: By analogy, a hybrid vehicle and a model T both have tires made of rubber (something in common), and things not in common (the unique design of their engine). The inference to evolution is like saying, "Well, because we know that hybrids and model T's are related, we can conclude that tires are ancient and inherited by both." That's an absurd inference.

When I worked in engine electronics engineering at Ford, my desk was less than 100 feet from what had been Henry Ford's old office back when the building was the primary Ford manufacturing facility. The Model T and any hybrid automobile that contains a gasoline/petrol-powered internal combustion engine may easily be shown to be derived from a common ancestor. Any two wheeled vehicles may be shown to be derived from a common ancestor; the material used for the wheel-to-road interface ("tyre") is a contingent detail. So, yes,

"...tires are ancient and inherited by both."

Henry J: What supports a theory is the patterns that occur repeatedly and consistently throughout the relevant evidence, of which nested hierarchy is perhaps the most important. There's also divergence of types over time, lack of types that don't fit in the heirarchy, geographic clustering of close relatives (at least with types that aren't globally mobile). On a side note, as I understand it, the geographic clustering was what initially caused Darwin to reach his conclusion. Without details on what "Intelligent Design" actually says (those do seem to be in short supply), with the simplest interpretation of "life was deliberately engineered" I would expected there to be massive exceptions to all of those patterns (e.g., frequent sharing of technology outside the taxon in which it originally appeared, geographic redistribution of derived species, species that don't fit the hierarchy, DNA differences that don't fit the hierarchy, maybe even species showing up long before several of their presumed predecessors.)

You characterize exceptions to nested hierarchies as a prediction of ID. Yet vehicles, which are obviously intelligently designed, have nested hierarchies. You have “Vehicle,” “Utility vehicle,” “Pickup,” “Extended cab,” “4WD,” colors, options, etc. It is easy to draw a nested hierarchy of automobiles.

Just skimmed this discussion. What ungtss is missing is a lot. Common descent is a fact. It was a theory at one time but that time was over a century ago.

We don't waste time reinventing the wheel each time we design a car.

The evidence is overwhelming.

1. Fossil evidence. These are tangible remains of ancient creatures that don't require theorizing to fit together. The link designating birds as avian dinosaurs was determined from a few fossils. A few more made it stronger. Then feathered dinosaurs were discovered. The hypothesis could have failed, instead it has become stronger and stronger with more data.

And contrary to the lies of the creos, we have lots of transition fossils. And more are discovered on a routine basis. Those gaps just keep getting smaller and smaller.

2. DNA evidence. When common descent was proposed in the 1800s, the mechanism of heredity was unknown. Mendel's dicovery fit right in. DNA was unknown. Nowadays, sequence analysis by machines that 2 decades ago were science fiction makes possible another test of common descent. It passed and we now use DNA sequence to determine the timing and branch points.

ID has been around in one form or another since the ancient Greeks. In >2,000 years it has gone absolutely nowhere and contributing exactly zero to science. These days it is just pseudoscience for religious fanatics from Death Cults bent on destroying the USA.

Richard Simons:

You characterize exceptions to nested hierarchies as a prediction of ID. Yet vehicles, which are obviously intelligently designed, have nested hierarchies. You have “Vehicle,” “Utility vehicle,” “Pickup,” “Extended cab,” “4WD,” colors, options, etc. It is easy to draw a nested hierarchy of automobiles.

It is indeed. However, if you prepare nested trees based on, say, the spark plugs, the speedometer or the seat covers, you will get different trees. In biology, you would get the same tree. Initially taxonomic trees of organisms were thought of in just the same way as you could think of them with vehicles. For example, plants were distinguished on whether or not they had seeds, whether the seeds were borne in flowers, whether the seedlings had one cotyledon or two and so on. However, it became apparent that organisms placed in one group had many different features in common and to a large extent it did not matter what features were used, an essentially similar pattern emerged.

This, basically, was the stimulus for considering common descent.

These days, data can be collected on all kinds of things, for example the exact distribution of the amino acids in proteins with specific functions. The data are thrown into a computer program that has no idea of what outcome is expected yet the resulting trees conform remarkably closely to trees derived from other data.

Richard Simons:

You characterize exceptions to nested hierarchies as a prediction of ID. Yet vehicles, which are obviously intelligently designed, have nested hierarchies. You have “Vehicle,” “Utility vehicle,” “Pickup,” “Extended cab,” “4WD,” colors, options, etc. It is easy to draw a nested hierarchy of automobiles.

It is indeed. However, if you prepare nested trees based on, say, the spark plugs, the speedometer or the seat covers, you will get different trees. In biology, you would get the same tree. Initially taxonomic trees of organisms were thought of in just the same way as you could think of them with vehicles. For example, plants were distinguished on whether or not they had seeds, whether the seeds were borne in flowers, whether the seedlings had one cotyledon or two and so on. However, it became apparent that organisms placed in one group had many different features in common and to a large extent it did not matter what features were used, an essentially similar pattern emerged.

This, basically, was the stimulus for considering common descent.

These days, data can be collected on all kinds of things, for example the exact distribution of the amino acids in proteins with specific functions. The data are thrown into a computer program that has no idea of what outcome is expected yet the resulting trees conform remarkably closely to trees derived from other data.

Richard Simons: It is indeed. However, if you prepare nested trees based on, say, the spark plugs, the speedometer or the seat covers, you will get different trees. In biology, you would get the same tree. Initially taxonomic trees of organisms were thought of in just the same way as you could think of them with vehicles. For example, plants were distinguished on whether or not they had seeds, whether the seeds were borne in flowers, whether the seedlings had one cotyledon or two and so on. However, it became apparent that organisms placed in one group had many different features in common and to a large extent it did not matter what features were used, an essentially similar pattern emerged.

This, basically, was the stimulus for considering common descent.

These days, data can be collected on all kinds of things, for example the exact distribution of the amino acids in proteins with specific functions. The data are thrown into a computer program that has no idea of what outcome is expected yet the resulting trees conform remarkably closely to trees derived from other data.

Henry J:

You have “Vehicle,” “Utility vehicle,” “Pickup,” “Extended cab,” “4WD,” colors, options, etc. It is easy to draw a nested hierarchy of automobiles.

Only by ignoring features of those vehicles that don't follow the same heirarchy. Engineers who design those vehicles are free to swap techniques, materials, or even parts, between all of those vehicle types, or even from other branches of technology. That swapping happens routinely in human technology. In contrast, in biology, afaik, nearly all the "technology" (as well as the DNA) is constrained by the same nest heirarchies, as long as no significant DNA swapping occurs between the species involved. The lack of that kind of swapping (copying verbatim a major feature developed initially in one taxon into a species in another taxon) would be expected if something were engineering the life forms, unless (1) the engineer(s) were deliberately simulating evolution, or (2) if there were something that prevented it or them from importing design information from species other than the one being designed at the moment. In case (1) we'd need some way to distinguish this from known genetic change processes, or else direct evidence of the engineering involved. (Some ideas regarding motivation of said engineers would help as well.) Case (2) looks to me to be very implausible, since any agency able to bioengineer species would be able to look around at already existing species. Henry

Wings appear in insects, mammals, birds, and reptiles. While they are all wings, they function in radically different ways.

Some sharks have live births. Others don’t.

ungtss -

I am not a biologist or scientist of any sort, but even I can spot the flaws in using convergent evolution to try to break biological nested hierarchies. I suspect you could too, if you just allowed yourself to think about it a little more.

Let's take your example of wings. If a bat had feathered wings structured like a bird's, then you'd have a good point and this would be a clear violation of the nested hierarchy predicted by evolution. That's not the case, however. First, bat wings aren't feathered. Second, if you look at the structure of a bat's wing, you see that it's clearly derived from the mammalian arm/foreleg primarily by elongating the finger bones. This is completely different than the bone structure of a bird's wing. In addition to comparing morphologies, you could perform genetic studies of bats and birds and their non-winged relatives to see the genetic pathways convergent evolution took. Again, they would be different as predicted by evolution. You can easily look all this stuff up on google. You can even see intermediates in the dinosaur to bird transition in the fossil record.

Rather than being a problem for evolution, the wing is yet another piece of evidence for it. Why do all bats have wings of one type formed by mutating the genes of their ancestors, and all birds have wings of a completely different type formed by mutating the genes of their own ancestors? Evolution explains why perfectly. All ID can say is "the designer must have wanted it that way". And yet again we see that while evolution makes predictions like nested hierarchies (that must match both morphologically and genetically) that could easily be falsified, ID is completely unfalsifiable.

AFAIK, everything I've written applies to all cases of convergent evolution. Certainly there are times when some simple mutation does result in convergent evolution in the exact same way in species that are only distantly related. Any complicated structure that has evolved more than once, though, is likely to be very different both structurally and genetically in its different incarnations. In every incarnation, however, it will be derived from structures and genes of ancestor species, not of species in other branches of the tree of life.

As I said, I am not a scientist, so hopefully if I've gotten anything wrong somone more knowledgeable will correct me.

A. White: ungtss - I am not a biologist or scientist of any sort, but even I can spot the flaws in using convergent evolution to try to break biological nested hierarchies. I suspect you could too, if you just allowed yourself to think about it a little more. Let's take your example of wings. If a bat had feathered wings structured like a bird's, then you'd have a good point and this would be a clear violation of the nested hierarchy predicted by evolution. That's not the case, however. First, bat wings aren't feathered. Second, if you look at the structure of a bat's wing, you see that it's clearly derived from the mammalian arm/foreleg primarily by elongating the finger bones. This is completely different than the bone structure of a bird's wing. In addition to comparing morphologies, you could perform genetic studies of bats and birds and their non-winged relatives to see the genetic pathways convergent evolution took. Again, they would be different as predicted by evolution. You can easily look all this stuff up on google. You can even see intermediates in the dinosaur to bird transition in the fossil record. Rather than being a problem for evolution, the wing is yet another piece of evidence for it. Why do all bats have wings of one type formed by mutating the genes of their ancestors, and all birds have wings of a completely different type formed by mutating the genes of their own ancestors? Evolution explains why perfectly. All ID can say is "the designer must have wanted it that way". And yet again we see that while evolution makes predictions like nested hierarchies (that must match both morphologically and genetically) that could easily be falsified, ID is completely unfalsifiable. AFAIK, everything I've written applies to all cases of convergent evolution. Certainly there are times when some simple mutation does result in convergent evolution in the exact same way in species that are only distantly related. Any complicated structure that has evolved more than once, though, is likely to be very different both structurally and genetically in its different incarnations. In every incarnation, however, it will be derived from structures and genes of ancestor species, not of species in other branches of the tree of life. As I said, I am not a scientist, so hopefully if I've gotten anything wrong somone more knowledgeable will correct me.

Henry J:

Wings appear in insects, mammals, birds, and reptiles. While they are all wings, they function in radically different ways.

Things that are radically different are not grouped together.

Some sharks have live births. Others don’t.

Yes, some different groups of vertebrates came up with that ability. Merely having an ability in common doesn't put things into the same group unless they got there in the same way. Henry

A. White: I am not a biologist or scientist of any sort, but even I can spot the flaws in using convergent evolution to try to break biological nested hierarchies. I suspect you could too, if you just allowed yourself to think about it a little more.

ungtss: But that’s where common descent is disputed

That’s an absurd inference.

This is not science. It’s speculation, premised on the assumption of common descent, and with absolutely no evidence, novel or otherwise, to support it.

Violations of the nested hierarchies may indeed be explained away by convergent evolution and horizontal gene transfer.

Unfortunately there is no theory of design, no scientific definition of “genetic entropy”.

But convergent evolution is really just an evolutionary explanations for the widespread and common exceptions to the nested hierarchies I was pointing out.

But that’s the point, friend. You said the groupings do not happen at the high levels I was discussing. But that’s where common descent is disputed – not at the local level. Nested hierarchies do not occur at the levels at which common descent is disputed! Also, grouping them by “whether they got there in the same way” is circular reasoning – the issue here is common descent, but in order to prove it, you have to assume that they “got there” by common descent.

Superficial similarities are useless for categorization, whether you believe in evolution or special creation or anything in between.

Ungtss wrote:

"But that’s the point, friend. You said the groupings do not happen at the high levels I was discussing. But that’s where common descent is disputed – not at the local level. Nested hierarchies do not occur at the levels at which common descent is disputed!"

I don't knw where you got this idea from, but it is completely wrong. There is a nested hierarchy of genetic similarity that extends all the way to the deepest branches of the tree of life. In fact, that is how the early branches were first discovered. The nested hierarchy corresponds precisely to the fossil record as well. Common descent is not an assumption of this data, it is a conclusion.

Using terms like "genetic entropy" just makes you look foolish. No such thing exists.

Henry J:

But that’s the point, friend. You said the groupings do not happen at the high levels I was discussing. But that’s where common descent is disputed – not at the local level. Nested hierarchies do not occur at the levels at which common descent is disputed! Also, grouping them by “whether they got there in the same way” is circular reasoning – the issue here is common descent, but in order to prove it, you have to assume that they “got there” by common descent.

Then let me clarify what I meant to say, since "got there" was ambiguous. It's the commonality of anatomy, DNA, and biochemistry that determine nested hierarchy. The fact that entirely different structures wind up performing a similar function is not a violation; biologists don't put species in taxonomic groups by whether they fly, walk, crawl, or swim, but by the structures used to do those things. Henry

I suppose I thought my proposals met the criterion you just cited: anatomy, DNA, and biochemistry. Wings are anatomical structures. Presumably at least some of the information required to construct them is stored in DNA.

A. White:

I suppose I thought my proposals met the criterion you just cited: anatomy, DNA, and biochemistry. Wings are anatomical structures. Presumably at least some of the information required to construct them is stored in DNA.

But the structures are totally different. The DNA is totally different. So how again does this break nested hierarchies?

Ungtss,

For some reason you are under the mistaken impression that classification systems are arbitrary, they are not. Cladistic analysis is based on synapomorphies (i.e. shared derived characters). This analysis yields the same nested hierarchy whether you use DNA or morphology. However, you must use characters that do not display homoplasy, (i.e. convergence or reversal), in order to construct a reliable phylogeny. That is why the hierarchy of plants, based on vascular tissue, seeds and flowers, gives exactly the same answer as the genetic hierarchy and the branching order is consistent with the fossil evidence as well. This is due to common ancestry.

As to how the characters evolve, in general different genes are used for cladistic analysis than those that are important in morphological evolution. This is for technical reasons such as avoiding complications due to selection and homoplasy. However, once a reliable phylogeny is obtained, then an examination of the molecular mechanisms responsible for morphological changes will be much easier since you will already know the sequence of changes and the timing of events based on the phylogeny. This can help to dientify the genes involved in morphological changes.

So, nested hierarchies are based on DNA and they give the same answer as hierarchies based on morphology. You can't compare the genes for making wings in insects and birds because they are not homologous and neither are the wings. Once again, you must compare structures and genes that are similar due to common ancestry, not just superficallly similar.

Of course I'm sure that Henry can explain all this as well.

By the way, snakes did not "develop feet". Cladistic analysis, based on morphology and genetics, clearly shows that snakes are reptiles, which are tetrapods. Limbs evolved in the ancestors of the tetrapods. Snakes evolved from four limbed ancestors and have secondarily lost their limbs. This has occurred many times during evolution and we now know some of the molecular mechanisms responsible.

Nested hierarachies are not consistent with ID, since God could presumably poof any structure into any organism magically at any time. For example, why couldn't some mammals have feathers? Why couldn't some birds have milk production? Nested hierarchies are only consistent with common descent. That's why independent data sets give the same answers.

Nested hierarchies are not "criterion dependent". they are dependent on historical contingency and evolutionary history. They are dependent on the branching order in the tree of life. God is not dependent on these things. If nested hierarchies were "criterion dependent" then the answers wouldn't continually surprise us and we wouldn't have to sequence any genes to find the answers.

If you really want to know the mechanisms of common descent, go back and read the start of this post. The placenta is a beautiful example of how gene duplication followed by divergence can generate novel structures. It is a general pattern observed over and over again in nature.

So, genetics can can not only provide answers to questions concerning the pattern of evolution, it can also provide answers to questions concerning the process of evolution as well.

You can dismiss me as a newcomer to the conversation if you choose, but if you check you will see that I made this exact same point two days ago in the seventh post in this thread.

David Stanton: Ungtss, For some reason you are under the mistaken impression that classification systems are arbitrary, they are not. Cladistic analysis is based on synapomorphies (i.e. shared derived characters). This analysis yields the same nested hierarchy whether you use DNA or morphology. However, you must use characters that do not display homoplasy, (i.e. convergence or reversal), in order to construct a reliable phylogeny. That is why the hierarchy of plants, based on vascular tissue, seeds and flowers, gives exactly the same answer as the genetic hierarchy and the branching order is consistent with the fossil evidence as well. This is due to common ancestry.

As to how the characters evolve, in general different genes are used for cladistic analysis than those that are important in morphological evolution. This is for technical reasons such as avoiding complications due to selection and homoplasy. However, once a reliable phylogeny is obtained, then an examination of the molecular mechanisms responsible for morphological changes will be much easier since you will already know the sequence of changes and the timing of events based on the phylogeny. This can help to dientify the genes involved in morphological changes.

So, nested hierarchies are based on DNA and they give the same answer as hierarchies based on morphology. You can't compare the genes for making wings in insects and birds because they are not homologous and neither are the wings. Once again, you must compare structures and genes that are similar due to common ancestry, not just superficallly similar.

Nested hierarachies are not consistent with ID, since God could presumably poof any structure into any organism magically at any time. For example, why couldn't some mammals have feathers? Why couldn't some birds have milk production? Nested hierarchies are only consistent with common descent. That's why independent data sets give the same answers.

Nested hierarchies are not "criterion dependent". they are dependent on historical contingency and evolutionary history. They are dependent on the branching order in the tree of life. God is not dependent on these things. If nested hierarchies were "criterion dependent" then the answers wouldn't continually surprise us and we wouldn't have to sequence any genes to find the answers.

David Stanton: If you really want to know the mechanisms of common descent, go back and read the start of this post. The placenta is a beautiful example of how gene duplication followed by divergence can generate novel structures. It is a general pattern observed over and over again in nature. So, genetics can can not only provide answers to questions concerning the pattern of evolution, it can also provide answers to questions concerning the process of evolution as well. You can dismiss me as a newcomer to the conversation if you choose, but if you check you will see that I made this exact same point two days ago in the seventh post in this thread.

nested hierarchies are based on gross anatomical characteristics.

Of course, you do have four wheel drive and two wheel drive appear in both passenger cars and pickups – so I suppose the drivetrain must be more “superficial” than the length of the cab.

Suppose I assume that internal or external birth are fundamental.

How did snakes develop feet?

How did reptiles develop the capacity to produce milk?

Those are the questions common descent needs to answer

Just because nested hierarchies are consistent with common descent does not support a conclusion of common descent UNLESS nested hierarchies are inconsistent with ID.

because hierarchies are criterion dependent

sonar

In fact, the argument comes down to selection bias. Scan the 10,000-some-odd ERVs in both genomes, find 1 or 2 in the same place, and conclude common descent.

It all comes down to that same inference -- which is philosophical in nature, not scientific. Nobody's arguing about the facts in front of us. We're all arguing about interpretations of facts that cannot, by their very nature, be directly observed.

But how do you know which characteristics were homology, and which were homoplasy? That depends, fundamentally, in the criteria one begins with.

Why couldn’t some birds have milk production?

ungtss said: Wings appear in insects, mammals, birds, and reptiles. While they are all wings, they function in radically different ways. Did all organisms with wings evolve from a common winged ancestor? Or did wings evolve independently in each of these taxa/clades?

If there was a common winged ancestor, then I guess the earliest mammal was a bat-like creature. But nobody appears to be making that argument. So it would appear that the view of the “scientific community” is that wings evolved independently. That is a violation of the nested heirarchies.

Sonar/radar also violates this rule. Bats and dolphins have it. So are we to believe that the earliest mammal had it and it atrophied in all mammals but bats and dolphins, or that it evolved independently?

As to the “DNA being totally different,” that’s not what nested hierarchies are based on – nested hierarchies are based on gross anatomical characteristics.

Then how do you know which traits exhibit homology, and which exhibit homoplasy?

Suppose I assume that internal or external birth are fundamental. The hierarchy starts to look different. Yet it seems to me that’s a much more fundamental characteristic than the capacity to produce milk.

Nothing about the facts necessitates common descent any more than it necessitates a common designer.

Ungtss,

You seem to be under the mistaken impression that biologists are all idiots and are only out to fool you. That is incorrect and illogical. Why would any scientist care what you think?

Homology is determined based on objective criteria. With genes there are statistical tests that can be employed to determine homology. With anatomy, homologous structures must be the same structure coded for by the same genes and produced by the same developmental pathways. Homoplasy in the data is reduced by careful examination of the characters involved BEFORE the clasdistic analysis is performed. We know the mechanisms of mutation and we know the relative and absolute rates of change for molecular characters. We avoid homoplasy by choosing characters that evolve at a rate appropriate to reduce the probability of convergence and reversal. The reasoning is not circular. The nested hierarchy is the result not the assumption.

As for endogenous retroiviruses (ERVs) or SINE insertions, we also know the mechanisms of transposition. There are literally millions of insertion recognition sequences in eukaryotic genomes. The probability of shared insertions by chance alone is extremely low. There is also no known mechanism for reversal, making this the perfect character for phylogenetics. Insertions persist through speciation events, thus shared insertions are strong evidence of common descent (the alternative being that God copied the mistakes). Now here is the important point, insertions are not only shared between species, but they are shared in a particular pattern, they are found in a nested hierarchy! In fact, it is the same hierarchy that is reconstructed by gene sequences, morphological analysis and the fossil record. Check out the Talk Origins archieve on plagarized errors in the Molecular Genetics section.

The nested hierarchy is exactly what is predicted by descent with modification. It is inconsistent with the hypothesis of a designer. If you insist that it is consistent, then you must explain why the designer created exactly the pattern that would be expected from common descent and no other. Is God trying to fool you as well? If so, you better play along, you know how she gets when she's angry.

Henry,

Thanks for the information. Of course this is just another example of superficial convergence. If the designer was responsible, I'm sure she could have done a much better job.