The discourse system just let me know i have earned another “merit badge” automatically awarded by the System.
I quote the text of the badge below (that particular posting has been accessed by 25 or more non-members).
And below that is the link to the article, on the rather amazing case study of a single population of marsupials (bottleneck count of the population not specified) who arrived on the Australian land mass when it was still connected to the other continents (from South America via Antarctica, before it ended up in the southern polar region).
Because this single population found no rival forms of mammals, more rapid speciation became a temporary norm, with phenotypes quickly diversifying to fill empty ecological niches!
From a single population (verified by modern genomic comparisons), at least three (3) new phenotypes emerged:
marsupial plant-eating underground moles;
marsupial meat-eating predator (similar to the Taz.Devil); and
omnivorous sub-populations collectively similar to bandycoots.
Its wonderful to have an open archaeological laboratory as big as Australia… with living successors available!
Nice Share This badge is granted for sharing a link that was clicked by 25 outside visitors. Thanks for spreading the word about our discussions, and this community.
Not sure what’s going on there, but I don’t see a link or an image. Here’s the link.
I’m also not sure what’s amazing about that case. It’s an ordinary phylogenetic study that shows Australian marsupials to be monophyletic, with the implication that South America is the ancestral marsupial home. Not sure what “unusually closely related” means either.
@John_Harshman It is not an image, it is the bolded text, above, stating that a prior post generated 25 or more hits by organic search from the outside. It means that something that was shared in the past is of interest to folks who are not already a member of the community. MC
I find it difficult to post linkless images with my android… so a picture of the merit badge is not provided by me… but any discourse member can see their own badges by clicking or right-clicking the menu(s) in the upper right corner.
The only link i posted was to the earlier post in another thread… and within that post is a link to the original article.
Sorry. I found the study much more interesting than the badge, and I found the quoted commentary on the study odd. The link I refer to was to the study. What’s a “teo”? Is that a typo or a term I’m not familiar with?
I believe the article itself has a more detailed discussion on genome relatedness for these branches off of a single genetic trunk.
As to the significance of all this, we frequently hear complaints from Creationists that examples of speciation are BORING…because all we have is a bird becoming a bird with slightly different coloring … or a fish with slightly different coloring - - not to mention all the cases of speciation where there isnt even a noticeable change in phenotype!
So here is a classic example where a single population created three distinct anatomies, three distinct life styles in three distinct niches within the Australian ecosystem!
No, it actually doesn’t. It shows that one retroposon unites three orders, which it agrees is weak support. There is no discussion of closeness of relationship, and rare events are a poor way to assess that. “Genome relatedness” and “single genetic trunk” are unfortunate phrasings, but I think I know what you mean.
That’s hardly rare. Plenty of phylogenetic studies do much better than that. Even with mammals, Afrotheria and Laurasiatheria are weirder collections. Not to mention Artiodactyla, which of course includes whales. And what about something as simple as Amniota or Tetrapoda?
1] I vaguely recall the article footnoting a citation for the study (studies) on the actual genetic testings. I am not literate in that kind of discussion. That is more of a @swamidass area!
2] Yes, rare events have their disadvantages. But perhaps it is better to think of the topic as a rare “multi-event” demonstration?
3] If you have an even better demonstration of dramatic changes in phenotype radiating out from a single population, i would certainly love to read up on it!
Don’t all dramatic changes in phenotype radiate out from a single population? Doesn’t every phylogenetic tree arise from a single population? That’s how common descent works. I have mentioned Afrotheria, Laurasiatheria, Artiodactyla, Amniota, and Tetrapoda as more dramatic changes. I’d mention some birds, but let’s face it: to the non-specialist, birds all just look like birds.
Huh? Are you just re-typing what i said and telling me about it?
Most Bird scenarios either lack in drama… or they lack in conclusive genetics.
Australia, except for recent imports, is devoid of placental rivals (bats are a notable exception because they can fly the ocean gap)… and in this case we have three VERY different animals.
They are not just “all kangaroos of different colors”.
As i said, if you have a BETTER case… please share. Im all ears!
Drama is in the eye of the beholder. Personally, I consider the relationship between grebes and flamingos quite dramatic. Not sure what “lack in genetics” means here.
I have already, by my count, shared 5 better cases: Laurasiatheria, Afrotheria, Artiodactyla, Amniota, and Tetrapoda.
Your economy of communication is MOST impressive, but not to be emulated.
Tetrapoda? You think the radiation of tetrapoda is a better case study? It is what we are trying to PROVE… because it is so hard to demonstrate to Creationists.
Amniota? How is that a better case study than my placentals in Australia?
What qualities in the study you cite make it easier to demonstrate to creationists than anything else? I’m interested in what you think would be convincing to a creationist, because I have never been able to convince a creationist of anything using any phylogenetic study at all.
Now, the cases I mentioned are better because the evidence is equally (or more) strong and because the morphological variety is greater within each group, which I thought was what you found exciting.
Are you asking for details because you don’t know them, because you think they don’t measure up in some way, or what? I would like to know before citing anything. For economy. I can’t easily think of anything more dramatic than a group than includes cows and whales (Artiodactyla), or one that also includes horses, bats, pangolins, and lions (Laurasiatheria), or one that includes elephants, dugongs, golden moles, and aardvarks (Afrotheria). I ask again: what about that particular Australian radiation is special to you?
You should read past the first sentence. Artiodactyla includes cows, hippos, camels, whales, and more. Laurasiatheria includes Artiodactyla plus horses, bats, pangolins, cats, dogs, weasels, and more. Afrotheria includes elephants, elephant shrews, golden moles, hyraxes, dugongs, aardvarks, and more. Each of these, of course, originated from a single ancestral species. Each of them tops “1 into 3” by a wide margin. Each of them is supported by much more data than the single retroposon supporting that marsupial radiation.
But with diffuse genetic evidence all over the map.
You are essentially saying:
The most persuasive evidence for common descent on Earth is all the examples of common descent we find in the world.
While true… its a bit circular. I am looking for a good looking BOUTIQUE example of radical changes in phenotype… and you are trying to sell me the wholesale catalog.
You dont really have the aesthetics of this project internalized yet, right?