Saturday, December 10, 2011

Ancestral relationships

Here is another example of cladists struggling with an ancestral relationship. Keep in mind that cladistics does not recognize ancestral relationships.
"There are currently two primary but competing views of azhdarchoid relationships. The first, presented by Felipe Pinheiro and colleagues in 2011, considers the tapejarids to be a monophyletic clade including the thalassodromines and chaoyangopterines.[4] The second, found by Lu et al. 2008 as well as Naish & Martill 2006, considers the tapejarids to be a paraphyletic [ANCESTRAL] grade of primitive azhdarchoids. All azhdarchoids closer toAzhdarcho than to Tapejara are included in the clade Neoazhdarchia("new azhdarchids").[2]"





If we analyze these two competing views they actually come down to two different conclusions about the ANCESTRAL relationships.
In the first view, Azhdarchidae is the ancestor (which is not acknowledged). In the second view, Tapejaridae is the ancestor (and is acknowledged).
Since cladistics does not even recognize ancestral relationships, the cladists are stymied about how to even think about these ancestral relationships.


  1. I am not claiming to know which ancestral relationship is correct. But (unlike cladists) I recognize ancestral relationships.

  2. Paraphyletic = Ancestral
    "The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic [ANCESTRAL] in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant common ancestor."
    "An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that differs markedly from the ancestral condition, and is thus not considered part of the ancestral group. The ancestral group will not be phylogenetically complete (i.e. will not form a clade), so will represent a paraphyletic taxon".

  3. Here is what I have been saying:
    "Paraphyly is a phylogenetic somewhat disparaging word for what is generally known as ancestors involved in macroevolution, that is, a label for a group from which one or more other groups at the same (or higher) taxonomic rank have apparently evolved. “Para” implies faulty, wrong, amiss, recrementitious, or merely similar to the true form. Evolutionary systematists, however, celebrate that which is presently known as paraphyly."

  4. No, the diagrams do not show that azdarchidae is the ancestor in one and tapejaridae the ancestor in the other. The first states that both Azdarchidae and Tapejaridae are monophyletic sister taxa. Neither are ancestral to each other, but do share a common ancestor. In the second "Tapejaridae" as defined in the first cladogram (i.e. including the Chaoyangopterinae and Thalassodrominae) is not a natural group, but two groups are closer to the Azdarchidae than to the members of the Tapejarinae. "Tapejaridae" in this case is still monophyletic, as explained in the caption quoted- Neoazdarchoidea contains all organisms more closely related to Azdarcho than to Tapejara- in fact that definition applies to both cladograms- they differ as to which groups they include within this taxon- in the case of the upper cladogram Neoazdarchoidea is synonymous with Azdarchidae. In the lower one it is not.

  5. A Nonny Mouse, do you understand what I mean when I say that cladistics does not recognize ancestral relationships?
    Do you understand what the other writer means by:
    "Paraphyly is a phylogenetic somewhat disparaging word for what is generally known as ancestors involved in macroevolution"?

  6. Cladistics is based on the idea of an unspecified common ancestor.
    This makes it impossible for cladistics to accommodate the reality of a real, specified ancestor.
    Cladistics has no way to handle a real, specified ancestor. That is why it leads to absurdities such as saying that:
    "An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that differs markedly from the ancestral condition, and is thus not considered part of the ancestral group."

    In other words, cladistics is forced to the absurd conclusion that an actual ancestor is not considered an ancestor. Because it has no way to accommodate an actual ancestor.
    This flaw is almost impossible for cladists to understand.

  7. Cladists claim that an actual ancestor taxa cannot be determined from the fossil record. But then they depart from this rule and recognize actual ancestors. This shows that cladistics is inherently contradictory. It acknowledges ancestors but then considers them not to be ancestors.

    With the rise of phylogenetic nomenclature, the use of evolutionary grades as formal taxa has come under debate. Under a strict phylogenetic approach, only monophyletic taxa are recognized.[6] This differs from the more traditional approach of evolutionary taxonomy.[7] The difference in approach has led to a vigorous debate between proponents of the two approaches to taxonomy, particularly in well established fields like vertebrate palaeontology and botany.[8] The difference between the statement "B is part of A" (phylogenetic approach) and "B has evolved from A" (evolutionary approach) is however one of semantics rather than of phylogeny. The two both express the same phylogeny, though the former emphasize the phylogenetic continuum while the latter emphasize a distinct shift in anatomy or ecology in B relative to A.

    This expresses the popular misconception. The issue is not just a "semantic" difference.
    Cladistics never allows itself to be pinned down to identifying an ancestor taxa. It is always an ancestor that is never found.
    Evolutionary systematics on the other hand does take a stand. Its proposals can be evaluated. Cladistic proposals, since they never identify an ancestor, can never be evaluated.
    This is a critical difference. It is disingenuous to pretend it is merely a semantic difference.

    The difference between the statement "B is part of A" [a clade labelled "A"] (phylogenetic approach) and "B has evolved from A" [A is an actual identified taxa] (evolutionary approach) is however one of semantics rather than of phylogeny."

    Note the clarifying words I have added.
    The label "A" is a DIFFERENT thing in the two approaches. In the first cladistic case, it is a clade name (representing an UNFOUND* taxa). In the other it is an IDENTIFIED, FOUND taxa.

    * Nobody has ever found a clade-named taxa fossil. It is a theoretical, unreal thing.

  10. The most credible thing is to always express a proposed relationship between taxa in non-cladistics terms. Express the relationship in ancestor/descendant terms.
    And if a relationship cannot be expressed that way, then be honest and say that the relationship is unknown.

  11. For those who wish to understand this subject better, I recommend:

    We can see from this reference that cladistics does not recognize ANAGENESIS.

    "Anagenetic component of evolutionary change is ignored in cladistics."

  13. I had posted earlier:
    "I am not claiming to know which ancestral relationship is correct. But (unlike cladists) I recognize ancestral relationships."

    By this I mean that (like evolutionary taxonomists) I include ancestral relationships (ancestors). I recognize them in the sense that I recognize that they must be included in any valid evolutionary proposal.

    Cladistics does not include them.

    "Ancestor: in this context, an organism, or more correctly a population, lineage, or species, that through evolution gives rise to one or more descendants that generally belong to a distinct taxon or species to itself. The identification of ancestors and descendants is a central aspect of evolutionary systematics. In contrast, cladistics denies it is ever possible to know an ancestor (unless one can actually observe evolution in a laboratory). "No matter how well we understand our group, its taxonomy, paleontology and anatomy, we can never know if one taxon is ancestral to another" (Paraphyly Watch blog - Transitional Fossils, Microbes & Patrocladistics). See also Ancestral group, common ancestor. (MAK)"

    "Ancestral group: I decided to adapt this phrase to refer to any supra-specific taxon or evolutionary grade which gives rise to another group. Examples include pelycosaurs, thecodonts, and condylarths. Ancestral groups are central to evolutionary systematics and often included in spindle diagrams. cladistics denies the validity of ancestral groups (see paraphyly). (MAK)"

    Evolutionary Systematics, also called Gradistic Taxonomy, gives an a dynamic evolutionary slant to the static Linnean system. It is based on a combination of branching and divergence. Most old books on palaeontology were based on this paradigm. Evolutionary Systematics was formulated by such "grand old men" of palaeontology as Ernst Mayr and G. G. Simpson. This approach accepts the Hennigian cladistic methodology as adequate for reconstructing phylogenetic trees, but retains paraphyletic groups (e.g. " Reptilia").

    Also, unlike Cladistics, with it's reliance on a hypothetical Most Recent Common Ancestor that is never actually described or discovered (a missing link that is always missing), Evolutionary systematics gives illustrations of the actual evolution of one species or higher taxon into another (as illustrated by the graphic at the top of the page showing the evolution of fossil horses).

    Admitedly, Evolutionary Systematics suffers from a number of shortcomings. For example the use of several very different criteria (phylogeny, divergence, adaptational level) to define particular taxa, as well as inconsistencies inherent in the paraphyletic approach (e.g. separating Class Aves (Birds) from the Archosauria). This, together with the greater rigour and precion of the and practical and heuristic superiority of the Cladistic (Phylogenetic) approach has meant that over the past decades.Evolutionary Systematics has greatly declined; the result being the rise of the dominant paradigm.

    Apart from my own good self I have only found one defense of evolutionary systematics on the Web - a lone voice in the wilderness, which you can check out if you want: Stanley Friesen explains why I prefer an evolutionary classification.

  16. Another interesting link:

    "Because of a misunderstanding between the respective functions and methodologies of evolutionary systematics (concerned with actual phylogenies in deep time)
    cladistics (concerned with statistically evaluating different phylogenetic hypotheses) it came to be wrongly believed that they were saying the same thing, that evolutionary systematics is a quantifiable result, and cladograms have to describe the actual evolutionary path of life. Such misinterpretations do disservice to both methodologies, but is surely one of the reasons for the decline and fall of evolutionary systematics. Nevertheless, a number of scientists, such as Richard Dawkins, Tom Cavalier-Smith and the authors of Res Botanica, support evolutionary taxonomy, although their criticism of cladistics only applies to literalist cladistics that mistakes cladograms for actual phylogenies. MAK111014

  18. Another valuable reference:

    "The rejection of naming tree nodes is said to be due to the fact that then all branches of a tree would need to be collapsed because a taxon cannot directly evolve from another of the same rank, according the th phylogenetic principle of holophyly. Classification by holophyly (strict phylogenetic monophyly) is artificial and leads to degenerate (as a return to absolutism) non-evolutionary classifications. Holophyly has no ontological basis as a process in nature, that is, it is not refutable and so is not a scientific hypothesis. It is ostensibly used for simplifying taxonomy, but in doing so requires one to lump and split taxa that in any way appear to represent macroevolution in classification. Holophyly clearly eliminates representation of ancestor-descendant evolution in classification. Thus, nodes cannot be assigned scientific names (other than a general and trivial attribution as ancestors belonging to the general group of all taxa distal on the tree). Not naming ancestors gives them an ineffable, metempirical, and recondite substance. It leads to faith-based taxonomy.

  20. The cladist's dilemma is that cladistics does not recognize (does not allow) ancestors, but the cladists themselves in fact do recognize ancestors. (See the examples above).
    Consequently they are forced to disown that ancestral (macroevolution) part of their knowledge and fudge the cladistic results to hide that fact.
    The result is that they are stuck with a "faith-based taxonomy".

  21. See here for an alternative understanding of polyphyly:

    "It has been suggested that paraphyletic groups be clearly marked to distinguish them from clades, for instance with asterisks: Reptilia*. The term evolutionary grade is sometimes used for such groups.[11]"

    I have seen a growing tendency for cladists to forget that the word "paraphyletic" (ANCESTRAL) has been considered by them to be disparaging (and considered invalid) and are slowly starting to accept "paraphyletic" as a valid relationship.
    This is wise but still does not save cladistics, because as long as it has the "ineffable, metempirical, and recondite" imaginary common ancestor idea, it is still a "faith-based taxonomy".

    This might sound odd, but paraphyletic groups are still used as they have a practical value for describing some groups. The most obvious ones to readers here are the dinosaurs. Birds are dinosaurs, that is, they are the direct descendents of an ancestor that spawned the dinosaurs, yet palaeontologists typically refer to dinosaurs while explicitly not referring to birds. Thus one should formally call them non-avian dinosaurs (basically all dinosaurs except birds).
    First off the rhamphorhynchoid pterosaurs (or more properly ‘rhamphorhynchoids’ as the quotes denote it as paraphyletic) which often come up here in my frequent posts on pterosaurs. As with non-avian dinosaurs, the term persists as one of convenience as basically it’s easier to write than “non-pterodactyloid pterosaurs”.

    Note the sleight of hand.
    The author says:
    "Birds are dinosaurs, that is, they are the direct descendents of an ancestor that spawned the dinosaurs".

    In other words, birds did NOT evolve from dinosaurs but rather (according to the author) birds and dinosaurs evolved from some OTHER unnamed common ancestor.
    But the author does not say this. In fact he compares it to the paraphyletic rhamphorhynchoid pterosaurs which is a true ANCESTRAL relationship (an ancestor of pterodactyls).
    He talks as as if they were the same relationship. Of course they are opposites - not at all the same.