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Mokele

Dolphin with hind limbs

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Quick, stop it before it evolves any further, crawls onto land, and defeats us with its superior intelligence!

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All hail King Snorky! Very neat little backtrack. Not sure if it's as cool as the toothed chickens, but almost. Yeah. I'm tired.

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Quote from SLC Punk:

 

Mark - "Did you know that dolphin is man evolved? I once saw a half dolphin half man in Greece."

 

I believe him:embarass:

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Quick, stop it before it evolves any further, crawls onto land, and defeats us with its superior intelligence!

"C'mon humans! We've wiped out entire species before! We can do it again!"

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A freak mutation may have caused the ancient trait to reassert itself, Osumi said. The dolphin will be kept at the Taiji museum to undergo X-ray and DNA tests, according to Hayashi.

 

If it's due to mutations, is it still considered evolutionary???:confused:

shouldn't it be like something new??

 

:D

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If it's due to mutations, is it still considered evolutionary???:confused:

shouldn't it be like something new??

 

:D

 

Evolution is change over time. You're confusing evolution with progress (i.e. successive as opposed to fluxuative changes)

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If it's due to mutations, is it still considered evolutionary??

 

Mutations are the raw material for evolution, so in that sense, all mutations are evolutionary.

 

However, the important part here is that it's not just some run-of-the-mill mutation like albinism, but rather that a mutation caused the expression of a hidden ancestral trait that was blocked until now. Essentially, it shows that all dolphins have a genes to build external rear limbs, but only this one has those genes active.

 

Mokele

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Mutations are the raw material for evolution, so in that sense, all mutations are evolutionary.

 

However, the important part here is that it's not just some run-of-the-mill mutation like albinism, but rather that a mutation caused the expression of a hidden ancestral trait that was blocked until now. Essentially, it shows that all dolphins have a genes to build external rear limbs, but only this one has those genes active.

 

Mokele

 

 

Ahhh, I get it (hidden ancestral trait)

thanx guys:-)

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I don't think this dolphins mutation can be written off as a re-asserted ancestral trait. The rear appendages are definitely flipper-like though smaller, but what are they attached to inside the body.

 

This picture of a dolphin skeleton shows that there is almost no pelvis or associated structures. The dolphin would have had to retain the DNA code for all these parts for 30-40 million years of significant morphological change accurately enough that a couple of mutations would allow the whole structure to to take its place in the dolphins body without gross-probably fatal- malformation.

 

I think that an xray of the dolphin is more likely to show a second set of vestigial shoulderblades and forearms due to an embryological accident. A rare event to be sure, but so long as the additional structures were behind the abdominal cavity it is more feasible that a working body would be produced. All the bones, nerves, muscular etc would grow according to the normal DNA instructions but from a starting point further down the spine. The lack of anchoring points for muscles that would normally attach to the ribcage would make the additional arms weak and reduce the flexibility of the dolphins spine and the whole assemblage would be smaller as it is further away from the source of nutrients, growth factors etc.

 

Of course it could be the evolution of a new species of which this is the first we have seen if there were some very strong evolutionary pressure for, say extra manouverability to avoid fishing nets...

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The rear appendages are definitely flipper-like though smaller, but what are they attached to inside the body.

 

The pelvis

 

This picture of a dolphin skeleton shows that there is almost no pelvis or associated structures.

 

That's a drawing, and a bad one at that. Googel image search "Dolphin pelvis". It turns up 27 pages of results.

 

The dolphin would have had to retain the DNA code for all these parts for 30-40 million years of significant morphological change accurately enough that a couple of mutations would allow the whole structure to to take its place in the dolphins body without gross-probably fatal- malformation.

 

There are no genes for arms or legs. Just genes governing bone formation, the formation of limb buds, etc. What determines if limbs form or not is whether these genes are turned on in the right sequence.

 

Some genes make structural protiens and the like, but many others govern what goes where, and most of the genes and regulatory DNA segments are involved in that. Organisms are only made of a few different things; what's important is when and where those materials are laid down and how they're shaped through development.

 

Remember, dolphins already have forelimbs, along with hindlimb vestiges. That means they've got the construction materials, and the developmental tools. On top of that, they develop limb-buds early in development, but the rear ones are terminated. All that needs to happen is for that termination to malfunction, and a good portion of limb development will proceed automatically.

 

If you think this is implausible, google scholar "talpid-2" and "chicken". Chickens with *teeth*. Real teeth. And it gets better: the developmental pattern of these teeth is archosaurian, the same pattern of crocs and, presumably, dinosaurs.

 

Mokele

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How can a dolphin have legs in addition to flippers? I thought a dolphin's flippers were actually modified legs, which is another thing that makes ceteceans different from fish (who have a bona fide tail).

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How can a dolphin have legs in addition to flippers? I thought a dolphin's flippers were actually modified legs, which is another thing that makes ceteceans different from fish (who have a bona fide tail).

 

Dolphins only have front limbs; there's remnants of a pelvis, but aside from this individual, none with rear limbs. They are indeed modified legs: the front legs became flippers, while the rear ones were lost.

 

Fish fins, however, are the same, since they're what limbs evolved from in the first place. Also, both have a tail.

 

 

Oh, wait, I get it, you think the fins at the tip of a dolphin's tail are it's rear limbs, yes? That's not actually correct; the flukes are merely extensions of the tail, not modified limbs.

 

Does that help clear things up?

 

Mokele

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Are there studies showing how experimenting with these mutated genes can benefit or inflict detrimental effects on the dolphins? As in, with their extra hind limbs, will it benefit the dolphins or does it cause the opposite effect? Or nothing interesting would happen. I mean the whole balance of the dolphins will be affected right? Or not since the extra limbs are light and will not make much of a difference. Would appreciate some explanations and clarifications.

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The animal is currently in an aquarium, and experiments are surely in progress as we speak. No doubt many scientists and grad students are slaving over these exact problems. But doing good science takes a while, so it may be a while before the results are published.

 

IMO, the rear legs are likely to be a hindrance due to extra drag, and possibly disrupting flow heading to the tail.

 

Mokele

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well we've seen humans with extra toes and deformations (from the norm), so I doubt this is a new thing on dolphins... There were proly dolphins out there with such disfiguration but we just never saw it...

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