The Opossum Files!: On June 6, philosopher Vincent Torley, one of our Uncommon Descent authors, asked us to consider the opossum as evidence for common descent:
Consider the opossum (a marsupial mammal): the evidence for common descent (Vincent Torley, June 6, 2016):
Remarkably, the recent spate of articles over at Evolution News and Views (see here, here and here) attacking the claim that vitellogenin pseudogenes in humans provide scientific evidence for common descent, all missed the point that Professor Dennis Venema was making, which was not about the existence of pseudogenes, but about the spatial pattern in the genes. The pattern is strikingly clear if we compare chickens with opossums. And since humans belong to the same class as opossums (namely, mammals), any scientific evidence that chickens and opossums have a common ancestor also counts as strong prima facie evidence that chickens and humans have one.
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An overwhelmingly strong scientific case can be made that life on Earth was designed. That alone should be enough to make belief in Intelligent Design reasonable. I believe that we in the ID movement should stick to our strengths. It does our cause no good if we query the very strong scientific evidence for common descent, which in no way weakens the case for Intelligent Design.
Ann Gauger of the Biologic Institute, has replied, disputing the matter:
1. Vincent Torley Thinks I Have Egg on My Face (June 10, 2016)
As a biologist, I see evidence on both sides of the debate. The evidence is equivocal — hence the fact that ID advocates take different positions on the subject. Yet common descent — the idea that organisms descend from one or a few common ancestors — is treated like a sacred cow by many scientists, and even, it appears, by some philosophers. Indignation arises that anyone would doubt it, would even have questions. Scientists take common descent as axiomatic, and accept evidence that is itself interpreted through a lens of common descent as proof of common descent. As a consequence, any evidence against common descent meets opposition and is explained away.
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If all people did was to read Venema’s post [to which Gauger responded ] the synteny would look pretty convincing. That’s unfortunate. Those not trained in science will take his post at face value, and be convinced of VIT1 synteny and its status as a former vitellogenin gene. When the original data is examined, it’s not nearly as convincing. Scientists have a duty to represent data accurately, even other people’s data. Now I may not have access to information Dennis Venema has, so I will give him the benefit of the doubt. But I would be happier if he changed his figures, or revealed his source for any data that didn’t come from the paper he cited.
2. Having a BLAST: The Torley Saga, Cont.(June 14, 2016)
Those who hold to common ancestry accept that, at the very least, each major group of animals is descended from a common ancestor, and some hold that the common ancestry goes all the way back to the first cell. The question at hand then is whether we share common ancestry with chickens and opossums, and by implication, with chimpanzees. What we have been discussing through all these posts is this: How strong is the evidence that we have the remnants of an egg yolk protein, vitellogenin, in our genome? Do we come from an egg-laying ancestor?
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There is definitely more similarity between chicken and humans than the Brawand paper reported. Why they didn’t report the full degree of alignment I don’t know.
Still, despite the increased alignment, this is on the borderline of what is detectable as a match. The fact that things vary from alignment to alignment indicates the match is weak. If there ever was a human vitellogenin gene, there’s almost nothing left of the original gene. Swamidass tells me that given the long time that has passed since our last common ancestor with chickens, this is to be expected. Yes, I know. But there is an alternate explanation — the possibility that a vitellogenin gene was never there to begin with — though I know Swamidass and Torley will vigorously disagree with me.
3. The Opossum’s Tale: The Torley Saga, Cont. (June 16, 2016)
Common descent cannot explain why egg-laying genes were lost earlier in one lineage than another, since it could have happened either way. Or not at all. See above.
From a design perspective, I would say the reason for the difference in apparent inactivation times is because each animal has a different design. How the DNA is used may differ.
So now on to the next and final explosive post. Stay tuned. It’s my riposte to the “explain and predict” test for common descent versus common design offered by Torley. And I am done with talking about egg yolk proteins.
4. The Placenta Problem: How Common Descent Fails (June 17, 2016)
Convergent design is clearly observable across biology but has no evolutionary mechanism. There are proposed reasons for it but no demonstration. I can hear in my head the arguments of evolutionary biologists: intrinsic constraints, canalization, living in similar environments or ecological niches, you have no demonstration either…
So then maybe the answer comes down to probability.
In considering these alternative explanations, ask yourself, how likely is it that a retrovirus would infect, invade the germ line (the cells that make eggs and sperm), then insert itself at random in locations in the genome that are expressed in the developing embryo or primitive uterus at the proper time, then promote fusion of membranes to permit the formation of a placenta, with all this happening at least six separate times in the six lineages tested so far? We should also make clear, expressing a syncytin by itself is unlikely to be enough to make a placenta, which is a complex organ requiring interactions between mother and embryo, and the ability to exchange nutrients and oxygen.
Readers? And over to Torley!
Fun: The cat wins, of course. Cats are unabashed creationists, as no creature could precede a cat in principle: