The Common Ancestor for the Australian Marsupial Dispersal?

The Common Ancestor for the Australian Marsupial Dispersal?

There are two great things about doing research on the evolution of Australia’s marsupials:
1] When you are wondering where to look for the successor population of a given population, if you are already in Australia, you don’t have to go anywhere else! If you can’t find the fossilized link in Australia, you know you aren’t going to find them somewhere else.

and 2] if you can differentiate the fossil of an extinct line of marsupials well enough, you don’t have far to go to study the genomes of the living successor population. If the fossil comes from a “dead end” population, the current living specie or species may not descend from the “dead end”, but they will at least be “cousin” lineages.

This thread is a review of the basic milestones of research in the radiation and dispersal of the Australian marsupials. In my view, the evidence arrayed in Australia is far more interesting and compelling than what we see in the Galapagos islands. Yes… the Finches there are very nice… but there’s only so much diversity on a set of islands, even isolated ones. While the Finches have diversified to eat different things and live in different ways, the usual YEC complaint is that they are still “just finches”.

However, if one branch of the finches (genetically related) looked and acted like a Bald Eagle… that would be a pretty good example of speciation - - even in the minds of some YECs!

Well, in Australia, we have that kind of radiation and dispersal in the “mammalian” realm of the marsupials. And we apparently owe the existence of all these types of marsupials to a single ancestral population!

Contents
1 Anteater-like
2 Cat-like
3 Groundhog-like
4 Mole-like
5 Rhinoceros-like
6 Panther like
7 Squirrel-like
8 Canine-like
9 Wolverine-like

But we’ll have to chase the rabbit a little bit to get to that “reveal”, because the “mother population” formed outside of Australia! But the branches that we follow within Australia apparently all lead back to that external mother population.

The link below is for an article that’s just 3 years old:
Mammals from ‘down under’: a multi-gene species-level phylogeny of marsupial mammals
by Laura J. May-Collado​, C. William Kilpatrick, Ingi Agnarsson
Published February 26, 2015 PubMed 25755933
.
.


.
.
Figure 1: Summary cladogram of all the analyses showing
support for relationships among major clades within Metatheria.


.
.
.
So, let’s look at the the “mother” of all Marsupials (later postings will “drill down” into the details):

Australidelphia is the superorder that contains roughly three-quarters of all marsupials, including all those native to Australasia and a single species [stranded] in South America. (All other … marsupials [in the Americas] are members of the Ameridelphia.)

Analysis of retrotransposon insertion sites in the nuclear DNA of a variety of marsupials has shown that the South American monito del monte’s lineage is the most basal of the superorder.
[Source: Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions
"Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions" by Maria A. Nilsson, Gennady Churakov, Mirjam Sommer, Ngoc Van Tran, Anja Zemann, Jürgen Brosius, and Jürgen Schmitz
PLoS Biol. 2010 Jul; 8(7): e1000436. Published online 2010 Jul 27. PMCID: PMC2910653 PMID: 20668664 ]

The Tracking Marsupial Evolution article tells us that kangaroos and opossums are the marsupials most closely related to placental mammals, “having shared a common ancestor around 130 millions years ago”.

The Australian branches of marsupials have been lumped together under the name Australidelphians as a continent-wide clade, for which the name Euaustralidelphia (“true Australidelphia”) has been proposed (the branching order within this group is yet to be determined).

‘Tracking Marsupial Evolution (2010)’ is quoted: “Australidelphia is significantly supported by both molecular and morphological data and comprises the four Australasian marsupial orders and the South American order Microbiotheria, indicating a complex, ancient, biogeographic history of marsupials.”

Further: “The four Australasian orders share a single origin with Microbiotheria as their closest sister group, supporting a clear divergence between South American and Australasian marsupials. In addition, the new data place the South American opossums (Didelphimorphia) as the first branch of the marsupial tree. The exhaustive computational and experimental evidence provides important insight into the evolution of retroposable elements in the marsupial genome. Placing the retroposon insertion pattern in a paleobiogeographic context indicates a single marsupial migration from South America to Australia. The now firmly established phylogeny can be used to determine the direction of genomic changes and morphological transitions within marsupials.”

In the first study mentioned above [Mammals from ‘down under’ (2015)] re-affirms the the conclusions from the older research:

“The study also showed that the most basal of all marsupial orders are the other two South American groups (Didelphimorphia and Paucituberculata, with the former probably branching first). This indicates that Australidelphia arose in South America along with the other major divisions of extant marsupials, and likely reached Australia [80 mya while dinosaurs still dominated] via Antarctica in a single dispersal event after Microbiotheria split off.”

More to follow …

2 Likes

This post is just to provide the separate link of the study mentioned above:

“Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions” by Maria A. Nilsson, Gennady Churakov, Mirjam Sommer, Ngoc Van Tran, Anja Zemann, Jürgen Brosius, and Jürgen Schmitz
PLoS Biol. 2010 Jul; 8(7): e1000436. Published online 2010 Jul 27. PMCID: PMC2910653 PMID: 20668664

Notice in the image below, the various branches associated only with South America, and branches associated with Australia, where “radiating” speciation continued, in isolation from the rest of the world.

[Be sure to click on the images to enlarge text to a more convenient font size!]


.
.
This image will be of particular value to us later on, because it creates a convenient grouping of some fairly disparate phenotypes:

While at the top we have “shrew-like” forms, and at the bottom we have “kanga” forms aggregated, in the middle grouping, we have the suggestion that three very distinct groupings share a close heritage:

Dasyuromorphia: the group having most of Australia’s carnivorous marsupials, including
quolls,
dunnarts,
the numbat,
the Tasmanian devil,
and the thylacine.
[In Australia, the exceptions include the marsupial moles and the omnivorous bandicoots.]

Notoryctemorphia: moles, vegetarian

Peremelamorphia: bandicoots & bilbies “the characteristic bandicoot shape: a plump, arch-backed body with a long, delicately tapering snout, very large upright ears, relatively long, thin legs, and a thin tail. Their size varies from about 140 grams up to 4 kilograms, but most species are about one kilogram, or the weight of a half-grown kitten [4 kilograms = 4 half-grown kittens].”
.

Tracking-Marsupial-Evolution-2010-Maria-Nilsson-02
.
.
This is the ideal “research scenario” to see how much genetic change occurs, and how quickly - - according to Evolutionary Theory - - to accomplish divergence into three distinctive “forms” of marsupials!

.
.

.
.
.
More later !

1 Like

Really excellent links and images too. Thanks!

I’m not sure this answers @Revealed_Cosmology’s questions though, does it?

1 Like

Not yet, @swamidass. First I needed to lay the groundwork for the radiating speciation, from a common ancestral population.

And so I found some very good sources of images and narrative for that. To answer @Revealed_Cosmology’s questions, or rather, some of his questions, I plan on drilling down into the genomes of the three central “sub-clades” of the Australian marsupials:
vegetarian moles,
carnivorous alpha species, and
the omnivore bandicoots et al.

This sub-clade (or aggregation of 3 sub-clades, depending on how you use the term) will demonstrate a sample of how much a genome has to change in order to produce shifts in phenotype beyond the trivial like “size” or “color”.

We have here genetically supported shifts in diet, shifts in eco-niches, and shifts in behavioral patterns that engage these other changes.

And we can then, for the sake of comparison, see how well these average shifts apply to the other legs of marsupial radiating speciation… even though these other legs don’t contain as much “shifting” in the phenotypes. It would be interesting if the rates of change are about the same, whether there is dramatic phenotype shifts or not!

SIDE NOTE:
This is parallel to what some young earth creationists propose happened once the animals were released from the Ark in Global version of the Flood narrative: YECs have to explain how we have more than a 1 or 2 million terrestrial species all in the 4000 years since the Great Flood. This is sometimes called Hyper-Speciation… which takes some of the air of the room for those YECs who think speciation of any kind is definitionally impossible!

PostScript: It may be that the best genetic details needed to answer some of Reveal’s questions is still not yet found published. If that should be so … then we will have tightly defined exactly what kind of genetic information is left to be obtained to provide the answers that all of us would find helpful to forecast the future of the study of speciation in general!

1 Like

Just to be clear, are you trying to show him evidence for common descent vs special creation by modification? Wouldn’t both models produce exactly the same data?

@swamidass,

My initial purpose was to develop a “reasonable standard” for how much change in a genome can take you from a generalized marsupial, to one specifically adjusted to a new eco-niche. With three different varieties, we can be sure that at least two of them are specific adaptations not found in the common ancestral population that migrated across the future Antarctica to exploit the future Australia.

As for providing evidence for “common descent”, it seems inevitable that in the process, we are going to learn some interesting things about the “nested hierarchies” embedded in the Australian marsupials, right?

The only defense against “special creation” is the same basic question: Why would God intentionally make his creation look like Evolution if he was going to simply “poof” these varied creatures into existence?

Australia is a great “work set” for multiple reasons:

  1. speciation in Australia has ideal conditions - - where there are no pre-existing tetrapods defending their prior occupany of any given niche. Fruit flies raised in a laboratory do not have the option of wandering around 365 days a year, probing virgin territory for advantages to exploit. The fact that Australia provides this opportunity without any intruders from elsewhere is far better than humans trying to intentionally create new environmental conditions in hopes of promoting speciation. Without such human intention, fruit flies would be no different from Alligators and Crocodiles who have existed for millions of years with very little change (except size).

  2. Australia provides all the evidence necessary to disprove the global flood (or evidence at least as good as the first 10 Egyptian dynasties!).

  3. Australia genome data can also probably provide important narratives for those who think Evolution can only produce “loss in complexity” … and/or that “degrees of complexity” is for the most part impossible to measure in the context of Evolution.

It doesn’t, for all the reasons I stated on the prior thread. I can still appreciate it for what it is, but we honestly have very little to say that there was a single species which the sole common ancestor of Australian marsupials. It’s only “evidence” for that if you already accept that this is what happened in the first place. It is particularly not evidence against the sort of scenario that I ascribe to, that something which is very much like TE was the goal, but this realm couldn’t do God’s will without God’s help. Just like us.

1 Like

@Revealed_Cosmology

I’m not sure you grasp the power of convergent lines of evidence in the defense of Evolutionary scenarios.
There is no other “natural law” alternative, in an Old Earth context, for explaining the diversity of marsupials in Australia.

The one alternative left to you, being one based in miraculous “special creation”, is to counter-argue that God used the basal genome of a Bandycoot-like animal, and intentionally used it:

  1. to “specially create” the appearance of a relationship with vegetarian, marsupial moles,
  2. to “specially create” the appearance of a relationship with carnivorous marsupial Tasmanian Devils, and
  3. to “specially create” the appearance of a relationship with leaping marsupial kangaroos.

How are you going to defend @swamidass’ scenarios if you reject God-guided Evolution, even when the convergence of evidence for the Australian marsupials produces a very persuasive case?

@Revealed_Cosmology,

I would like to point out, again, that if you are Old Earth, and the @swamidass scenarios provide for the Special Creation of Adam and Eve 4000 years ago … what exactly poses any difficulty that God-guided Evolution for the creatures outside of Eden?

Until the Swamidas breakthrough, it was an either/or kind of question. But now… we can have both.

And yet you still set your heals down, saying that speciation is impossible. Unless God is imposing some kind of supernatural force on chromosomes, there is really no way to prevent speciation.

Genetics determine sexual reproductive compatibility. And if 2 or more populations are separated long enough, it is very difficult to imagine that, past a given threshold, changes in the genome in one population won’t interfere, ultimately, with viable reproduction with members of a significantly different population and genome.

That’s why Horses and Donkeys only produce sterile mules… genetic incompatibility.

Do you think God has used his supernatural powers to limit the ability of genes or chromosomes to experience differences that affect reproductive compatibility?

One of our goals: to unify the views of two different camps:

1] one that believes there is too much evidence for Evolution in the fossil history to ignore,
2] while the other believes there is too much Biblical investment in the special creation of humanity to ignore.

You seem to not be in line with this dual-pronged mission…

I do not say that, and correcting your repeated efforts to ascribe that position to me has become tiresome. If you can’t get that, then again describing my more nuanced positions to you will be a waste of effort on both of our parts.

To the contrary, I have the very biblical model which does reconcile these two “missions”. If no one bothers to examine or understand it, that’s not my problem. I’m actually in pretty good scriptural company. My only obligation is to share what has been given to me. Results are in His hands.

1 Like

Hey, @Revealed_Cosmology, that’s a new idea I hadn’t noticed before. If one of the missions is:

to embrace the camp of Christians “…that believes there is too much evidence for Evolution in the fossil history to ignore…”, are you saying you have scripture that defends that mission?

Well, what scripture is that? But I think I must be misinterpreting what you said above. Please explain and I will listen.

1 Like

@Revealed_Cosmology has been pretty clear about this.

  1. He thinks the Scriptural case for a genealogical Adam is strong.

  2. He is unconvinced by unguided evolution and common descent.

  3. He still is not opposed to evolution, and is not going to invest time arguing against it.

Totally reasonable.

For these reasons he is on board with what we are doing here, and occasionally asks questions about evolutionary science.

You have more in common than you think. Give him time to figure things out for himself, and know he still might disagree at the end of the day. Having OECs around is a good thing as it build a bridge to the RTB crowd too.

1 Like

Three passages from my book although I fear it won’t make much sense without the ground work being laid. The text really is describing a middle ground…

"That being said, if ever there was a day and an area of creation in which earth responded without His further intervention it was within this third day. God commanded the land to bring forth vegetation (the “grass” in the King James is misleading) and seed plants and fruit. The earth then did so without it being recorded that God did anything to help the earth do it.

What I am getting at is that plants seem to be more likely candidates for “Theistic Evolution” than creatures of the sea or land, or certainly Mankind itself. God simply produced the initial conditions in which plants could thrive and then commanded that the earth produce plants. That sounds a lot like God simply got things set up right and let the creation itself handle things from there. If any form of life is subject to “macro-evolution” its plants.

Not only that, the Earth could have still continued this process and be continuing it today. God did not need to directly do anything else in order for the Earth to bring forth such plants. He never told the earth to stop bringing forth plants. So it is reasonable to suppose that the earth continued to bring forth different seed plants and fruit plants on days four, five, and six- and that it is still doing so today. "

and

"In theistic evolution God designed the universe to unfold in such a manner that advanced life would be the result even if He never intervened in the natural universe after He created it. That is not what the text in Genesis one describes.

Rather, God intervenes repeatedly after the creation of the universe. He has to create the templates or first examples. Only then can nature fill the seas with creatures of that type in accordance with His directive. To obey God’s command and fill every niche of the seas nature may produce variations within a kind, but they are variations on a theme produced by God. Maybe there is more variation within a kind going on here than a strict creationist would be comfortable with, but there is surely more Divine Creation going on than an evolutionist would be comfortable with.

and

If you have been following along with me, by now you see the pattern. In verse twenty-four God initiates the sixth day by commanding the land, in whatever realm it may be natural or supernatural, to bring forth living creatures after their kind. The land in the supernatural realm, the third heaven, does so immediately and exactly as God says. High Heaven then reports “And it was so.”

But while the land above performs His word completely, we learn in verse twenty-five that in our world God Himself must act in order to fulfill His word. Our natural world can’t seem to get started until God makes “kinds” of land animals. Unlike in the heavenly realm, the earth only brings them forth after God has made the kind, or category, for the earth to work with.

Notice that the word “made” is used here, not “created” as was used on day five. Again, this indicates that God was basing something in this realm off of something which already existed in the realm above. He was working from a heavenly pattern- like the tabernacle on earth was built on a heavenly pattern. When the work was done the natural realm reported that God “saw that it was good.” Maybe not perfect, as in the world above, but suitable and attractive nevertheless.

Ironically, what occurs in the land above sounds a lot like “theistic evolution”. God commands the land to bring forth the living creatures by kinds and the land does so. But it is not our land. It’s the land those who love God will enjoy in the life to come. Down here on earth, creation can’t pull this process off without God’s continued direct intervention. God has to “make” the land animals kind by kind. He puts on the earth patterns of what is heaven and the earth then takes it from there.

In this view of things, the many disputes between those who think life diversified via theistic evolution versus those who believe God used direct creation seem almost irrelevant. Which view is correct? Well, both are correct in their respective realm. On the one hand, in the realm we live in God had to directly make prototypes of the animals by kinds. So that’s divine creation. On the other hand, its only divine creation because this realm doesn’t have it together yet- what happened in the land above looked more like theistic evolution.

According to this passage that is not what happened down here though. God directly intervened and got things going for “the land.” In the record of nature that might still look a lot like theistic evolution, because nature (the land) was working off of a pattern which worked very much like “theistic evolution” in the heavenly realm. In this mixed realm of darkness and light, the land could not pull it off alone. God had to step in and make examples for the land to work with, called “kinds”. So both sides are right and both are wrong. Can’t we all just get along here?

To be a little more exact…

(I think GA shares the correct model of early Genesis, which I call the “Christ Centered Model” which I received independently from looking at the scriptural, not scientific, evidence. I still don’t know if GA within that framework is strictly necessary, but am 100% onboard with the model or framework which GA proposes, and have the synthesis of scripture necessary to support it.)

(As a total explanation. I think it was what nature was trying to do, but could not pull it off without further intervention at some points.)

(Unless provoked)

1 Like

Well, evolution is not a total explanation. So what exactly is the debate about?

Oh yeah…

7 posts were merged into an existing topic: Octopus not an Extraterrestrial

@Revealed_Cosmology (and @swamidass ), you’ll be happy to know that your posts have helped me identify why I have a problem tracking your views.

I earlier posts, you were discussing why you thought Australia’s marsupial evidence doesn’t convince you about Evolution. You see, I’m used to Christians who either favor “Evolution” that God doesn’t guide… or Christians who favor Evolution that God works through constantly - - the so-called “God-Guided” Evolution option.

It never occurred to me that anyone had developed a third option. So @swamidass, make sure you read his prior posting that I’m quoting here. It is a NOT chocolate or vanilla. It’s something completely different.

But before I get to my specific comments on this third option, I should point out that your third option really doesn’t embrace the Evolutionary camp in my “twin-edged” analogy. No… your position replaces that camp. Even though the camp already confesses “God’s Guidance”, it is still inextricably connected to the principles of “Common Descent” and the use of “Natural Selection” by God.

And so what I have been wondering about has been answered. And @swamidass, you should read for yourself why @Revealed_Cosmology’s scenario is neither Milk nor Cream: it is half and half. He thinks the so-called term Macro-Evolution is really more applicable to plants, not animals. And rather than a chain of common descent, he sees a “chain of special creations”, with minor speciation occurring between the events of special creation: "Rather, God intervenes repeatedly after the creation of the universe. He has to create the templates or first examples."

Well, now that I’ve seen how complex your version of serial Special Creation is, we can discuss it out in the open.

Firstly, your Half-and-Half dairy substitute is not going to satisfy the Christians who believe there is too much evidence for Evolution (with Common Descent and Natural Selection) to be ignored. Why? Because you are ignoring the evidence, of course.

How so? Well, let’s go back to the Australia example. It appears that you are either going to say that the Tazmanian Devil, Marsupial moles and Marsupial Bandycoots are either “just variations of a single kind” - - or you are going to agree that they are significantly different, and so God created each template [ by means of special creation ] and evolution can proceed from each template.

I completely reject the first conclusion: I offered Australia as a laboratory set specifically because the three groups of marsupials are clearly and significantly different. You cant compare a ground-sprinting carnivore with a subterranean vegetarian mole and say they are “basically the same”.

And I reject the second conclusion even more energetically. Why would god use a bandcoot genetic template to create a mole? This genetic evidence tells us that either God uses natural selection and common descent as one of his tools for animal creation, or that he is intentionally trying to make us think he does.

So, am I happy now? No. I’m even more distressed than I thought I would be. Because you not only reject the evidence for common descent that unites all the animal phyla, you even propose that once God makes each template [by Special Creation] he then ignores the resulting minor evolution that might happen after each template is established.

This seems as such an utterly un-necessary position - for three reasons:

  1. I can’t imagine a hybrid position more complex,
  2. a hybrid position less supported by the natural evidence, and
  3. a hybrid position less popular with Christians who “adhere to the idea of
    Common Descent because there is no reason not to”.

@swamidass, I’ll leave you two to discuss more if you like. But I’m satisfied that I finally got the explanation that I was seeking all this time.

While @Revealed_Cosmology rejects Common Descent (except in the smallest pockets of species), he actually rejects God-Guided Evolution rather thoroughly - - since in his own words he says God doesn’t really need to do anything once he has made his long chain of Special Creations. The irony here is that he is actually more comfortable with un-guided Evolution, but only if it deals with minor variations - - because the big variations are due to God’s special creations of a sequence of Templates, rather than due to nature’s ability to create dramatic speciation by means of Natural Selection (with or without God guiding mutations and changes in the environment).

I am saying that we lack the controls/info necessary to determine which of those options or a third option actually occurred. Or it could be that they all radiated from a single ancestor as you propose simply using the methods God set up, but gaps bigger than that needed more direct Divine input.

@swamidass

The debate is about a third category of mixing “special creation” with “minor common descent”.

Even your compromise position of your scenario is not a “fit” for his approach.

All you are doing is re-stating the exact two options that I described - - both of which I completely reject.

You are a “third way” that doesn’t fit the natural evidence… but fits your view of the Bible just fine.

PostScript: Natural Selection and mutation (both of which can be influenced by God’s will) are perfectly able to generate the large and the small leaps we see in the fossil record and are consistent with what we see in the genetic evidence. And you reject that analysis, in preference to thousands of separate and specific “special creations”. I see these “special creations” as only occurring in Eden, with a limited number of animals that have already been created outside of Eden by means of God-Guided Evolution.