This is a companion discussion topic for the original entry at https://biologos.org/blogs/guest/four-amazing-examples-of-historical-science-in-action
This is a companion discussion topic for the original entry at https://biologos.org/blogs/guest/four-amazing-examples-of-historical-science-in-action
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I’ll be available here for discussion. Any comments, questions, or objections are welcome.
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How nice to have these examples summarized and compiled in one place. Bookmarking for future reference. 
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[quote=“Casper_Hesp, post:2, topic:37426, full:true”]
I’ll be available here for discussion. Any comments, questions, or objections are welcome.
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Well, you sure know how to play to my weakness! As you know, Australian fossil evidence has always
been particularly compelling to me.
And so your exhibit sent me right into orbit!
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Let me ask one clarifying question… are you saying that science has already confirmed that all the marsupials we find in Australia (alive or as fossils) can be shown, via anatomical or genetic inquiry, to all originate from a single branch of the marsupial tree of common descent?
Naturally, I always suspected that would be shown - - but I was never brave enough to say that it “probably has been” shown !!!
Wonderful work, @Casper_Hesp - - my enthusiasm for the article is beyond explication (which is why I am using such an awful word like “explication” !) 
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I can answer this:
Yes. Genetic studies have already demonstrated this!
(Like you, George, I find the marsupial data to be among the most compelling. And so does Darrell Falk, which is why it forms the backbone of his Coming to Peace with Science, my go-to lend-out-to-interested-Evangelical-friends book.)
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Thank you, Dennis. I am especially glad to hear that from a biologist like you, given that the parts involving biology are (admittedly) outside my field of expertise. I do work on evolution of the brain in my neuroscience programme, but the “genes” in my evolutionary algorithms are only distantly related to actual genetics. Your evolution/genetics articles on BioLogos have been useful for me, in addition to what I’ve learned in my university courses that touched upon the topic.
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Let me put in a plug for Neil Shubin’s “Your Inner Fish”. He lays out the reasoning that allowed him to narrow in on a small spot of land on the east (if my memory is correct) coast of Greenland as a probably location for the fossil he was looking for. When you consider the odds of just wandering out in the field and finding the one fossil you were looking for you can’t argue evolution isn’t real. It’s like walking up to a hay stack and knowing exactly where to reach in and pluck out the needle.
All in all it is a great little book.
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Thank you for your kind words, George. I was actually thinking about you when writing up the section about marsupials. I agree with you that this example is an often underappreciated success story of evolutionary science!
Genetic data indicate that all present-day marsupial species (in the Americas and Australia) descended from a single ancestral population of marsupials (remember this from the discussion about the single human ancestral population? 
). Also, all marsupials share a unique reproductive system, which is unlikely to have evolved twice separately in that specific form (though if that had happened, we would be seeing that in the genetic data too).
As far as I know, only the precise relationships among very closely-related species within the clade of marsupials are still in flux (especially those that are extinct are difficult to pin down). That variation falls within the boxes in the figure, so it does not affect the overall pattern shown here.
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