Did We Have "Reptilian" Ancestors?

Because I see no explanation for this to occur from ancestry alone that seems probable. Perhaps you do.

So you pull out the evolutionist “all the overwhelming evidence canard” to battle the creationist canard. Your level of certainty is not warranted and only due to your commitment to the paradigm.

You have yet to support this claim by clearly describing an objective test that would reject the hypothesis in one case and accept it in another.

Based on the working assumption that all Tetrapoda share a common ancestor.

Thanks, that’s interesting. If parsimony rules, when would we expect (or how would we determine) that an incomplete appendage was some new feature that was under development rather than an old feature fading away. (I’m certainly using the wrong technical terms, so please extend a little grace here.) It would seem that if one were to go back in time, they would find an ancestor that had to go through a similar process of growing legs or fins, for instance.

Finally, are there any species alive now about which scientists are able to point out new features that are developing (as per my initial question?)

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It’s unclear what you mean by “from ancestry alone”. Do you mean that you think gene loss doesn’t happen? Does it mean that the same gene can’t be lost in two different species independently? Does it mean that you think it can’t happen as often as required by phylogeny?

How would you know? You’ve never looked at the evidence, despite my having sent you to it many times.

That’s true with most statistical tests. You can either reject the null hypothesis or fail to reject it. You can’t accept the null hypothesis. In this case you can consider “no tree” as the null hypothesis, and in the cases at hand we can with high confidence reject it in favor of the particular tree supported by the data. Now go back and look at the papers to find the statistical tests performed in them.

Based on the masses of data showing that all Tetrapoda share a common ancestor. Again, have you ever looked?

That’s a technical question, hard to answer except with pictures of trees and complex character coding. But if the ancestor had legs, and they resemble in detail the new appendage we find on that occasional whale, to suppose that it’s a completely new feature would require that all those details arose coincidentally rather than being retained, unexpressed, from an ancestor. Too many coincidences are unparsimonious.

There’s rarely anything in the history of life that’s a completely new feature. Most new features arise from changes to old features. And how would you recognize an incipient new feature to distinguish it from a minor variation? How can you tell if a new feature is going to develop any further? This really isn’t something that could be recognized except in retrospect. I could show you plenty of new features in retrospect, but I don’t know how to show you one that’s happening now.

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A post was split to a new topic: Greg On The Odds of Macroevolution and Vegas

Thanks for your response… I know that the example being discussed here was the whale, but I meant the question to be less specific, so feel free to answer it in general if this is not a good example. I often hear of specific items of interest (functions) being referred to as vestigial, but I never hear of these kinds of things being discussed in terms of being newly evolved functions.

That make sense, so you look back at the predecessor to see if it possesses a similar feature or function, if so it can be said that it was likely to have inherited the function or feature from that earlier species?

We all know that, assuming common descent, that every function or feature was once new. How did parsimony come into play earlier on then? It seems to me that as we look further back in time, we see species develop from much simpler species from which a library of functions and features were not available to contribute to the newer species.

It seems as though novel features came about, initially at least, in an environment where there were there was very little prior work from which to draw (changes to old features, as you have described), and further that parsimony did not seem to come in to play as it does now.

I realize that my questions and scenarios are gross oversimplifications, but I would imagine that scientists in your position must wrestle with these questions also, if they don’t already have good answers for them. I welcome other scientists to chime in, also. This is one of the ‘stumbling block’ areas for me as I try to wrap my brain around how evolution can explain the breadth of species that existed over time.

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So you’re looking for something that looks the same as a vestigial organ but is instead newly evolved? I don’t think new functions begin as vestigial organs.

Roughly, though of course we can never say that this predecessor is an ancestor. We reconstruct ancestral states based on the phylogenetic tree.

It’s surprising how rarely anything truly new happens. Of course it does sometimes, but even then it’s hard to recognize it as new. Lungs, for example, likely began as just a section of the pharynx with a few more capillaries than usual, then as a depression in the pharynx that increased the vascularized area, then as an outpocketing. Enough little changes, and you have a new organ. But where’s the new bit? It’s just a combination of pharynx and capillaries. Do we then have to go back to the origin of the pharynx and of capillaries? But they come from prior parts too. There’s so rarely anything that’s fundamentally new in evolution.

Not sure what that means.

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In addition genetic studies show all extant cetaceans (and sirenians and pinnepeds) have the functional but unexpressed Tbx4 genes for hind limbs in ther genomes. Atavisms occur when an occasional mutation reactivates all or part of the leg forming genes.

Sequence Variation in the Tbx4 Gene in Marine Mammals

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Look over there Bill! It’s a shiny thing!!

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Thanks again, John. I didn’t mean that exactly. I was referring back to the example in this thread. There was a whale that have vestigial hind limbs. Those limbs were referred to as being leftovers, so to speak, from the predecessor. These “hind limbs” were said to be remnants from a four-legged land animal from which the whale evolved. So, my question was regarding why, when we see something like the remnant of a hind limb that is not used by a whale, it is assumed to be a remnant from the past rather than something developing for the future.

The reason for asking this question is because of the next point that I make… namely, that if you go back far enough in time, you will find very simple animals. From that point forward, all of the functions or features that we see in the more complex animals are, in essence, new.

So, if we say that very early, very simple animals had “tissue” and “skeleton” for instance, then I guess you have the ingredients that you need for “tissue” to become “trachea” and then “lungs.” But, while one can look back in retrospect to see that lungs were merely tissue, once, the entire process still seems to go against the rule of parsimony. It seems that all of the function that did evolve over time should not have been expected to have done so.

This is interesting. So in the whale example above, there seems to be naturally occuring hind limbs, but they are not fully developed and are described as vestigial. These “limblets” seem to be normal (I know nothing about whales, but the thread above seems to indicate such.) So what is the difference between the vestigial limblets shown above and an animal where an atavism occurs? Are you saying that a fully formed limb, rather than a limblet (sorry, my silly term) would be there? Would it be a whale with a true hind leg, flesh and all? Is there a picture of anything like this that can be seen?

Again, because of the history of the lineage. Also, things don’t develop “for the future”.

You might think so, but it rarely works that way. Like the lungs.

I do not understand what that means.

I agree that we have no way to predict what will happen, if that’s what you mean. If that’s not what you mean, I don’t know what you do.

None. It is in fact an atavism, and most whales of that species lack those vestigial limbs.

You’ve lost me now. “Would be there” under what circumstances? Nobody says that any such thing has happened.

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As a yec who insists whales did come from a landloving origin the vestigial bits are important. My fellow yEC who don’t agree whales came from the land will say the hind leg bits have a function in sex. So not legs that have atrophied. Biologists also say they are used and thats why they didn’t evolve away.
still its excellent evidence for once having legs regardless of how now used. Indeed I understand fiull legs or something very often grow in some…
Marine mammals are great cases for important bodyplan morphing but not for the mechanism and its rarity is damming evidence against evolutionism.

The “limblets” in the photo are an atavism, a rare re-emergence of a feature on an individual animal The gene which produced them is vestigial and found in all whales. There is more than one gene involved in producing an entire functioning leg with feet and digits. What normally happens with an atavism like the one show is only some or one of the vestigial genes gets expressed due to a mutation. That means you only get a part of a hind limb, not the whole thing.

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Here’s one example. There are insects called leafhoppers, closely related to cicadas, known for having all sorts of strange protrusions called “helmets” on their backs. The helmets function as mating display, camouflage, predator defense. A few years back genetic studies showed the helmets were actually a modified third set of wings growing from the insects’ thorax.

Body plan innovation in treehoppers through the evolution of an extra wing-like appendage

Evolution never sleeps. :slightly_smiling_face:

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Thanks @John_Harshman and @Timothy_Horton for the clarification. I misunderstood and thought that the atavism (the “limblets” above) existed naturally. It was a genetic defect, so to speak. This caused confusion over your comment regarding parsimony, which is why my questions did not make sense.

It still seems to me that it is fairly gratuitous to believe that new developments are a rarity, though. I can see how one can claim that at a certain point a trachea becomes a lung, but it seems as though the same rule of parsimony that was called upon in the earlier example, would also be an obstacle in this case (and all other new developments) too. If evolution is so economical or conservative that it would normally preclude a limb, which had readily evolved previously, from evolving again in the same way, why would it not also apply the first time?

Why would the evolution of the limb be easy and assumed the first time, and yet parsimonious and unlikely the second time? Do you see a conundrum here, too?

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For a feature like a limb to re-evolve in a lineage a second time would require a duplication of the original environmental selection pressures, a duplication of the available ecological niches, etc. The chances of such conditions being duplicated is vanishingly small. There is at least one known instance of something like that occurring however. In the lineage of stick insects (order Phasmatodea) there is fossil evidence the lineage evolved wings, lost them, then re-evolved them, possibly more than once.

Loss and recovery of wings in stick insects

The evolution of wings was the central adaptation allowing insects to escape predators, exploit scattered resources, and disperse into new niches, resulting in radiations into vast numbers of species. Despite the presumed evolutionary advantages associated with full-sized wings (macroptery), nearly all pterygote (winged) orders have many partially winged (brachypterous) or wingless (apterous) lineages, and some entire orders are secondarily wingless (for example, fleas, lice, grylloblattids and mantophasmatids), with about 5% of extant pterygote species being flightless. Thousands of independent transitions from a winged form to winglessness have occurred during the course of insect evolution; however, an evolutionary reversal from a flightless to a volant form has never been demonstrated clearly for any pterygote lineage. Such a reversal is considered highly unlikely because complex interactions between nerves, muscles, sclerites and wing foils are required to accommodate flight. Here we show that stick insects (order Phasmatodea) diversified as wingless insects and that wings were derived secondarily, perhaps on many occasions. These results suggest that wing developmental pathways are conserved in wingless phasmids, and that ‘re-evolution’ of wings has had an unrecognized role in insect diversification.

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I am really impressed with your vast amount of knowledge. Reading this i admit i might be misunderstanding a bit but this soundbite seems to be justifying Behe’s claim of devolution where in time a species will lose adaptative traits needed for survival for them to never be regained-all countering neo darwinian theory. Prior to this statement you seem to give evidence for evolution but this seems very opposing…again, if i am understanding correctly.

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You have to understand that when legs first evolved they didn’t suddenly spring from the body. The first true tetrapods evolved from shallow water fish. So what happened was that the fins of the fish gradually evolved into legs. That means there was already a functional structure there with a clear adaptive benefit. The fish could swim with their fins, and even “stand” on them and support their body weight when in very shallow waters.
Here’s a nice video that shows “walking” fish that live part of their life on land:

Compare how they walk by wiggling their body side to side, to how this salamander walks:

The shallow water environment like a beach area or flood delta where mudskippers live, provided the originating selective pressure that turned ancestral fins into legs.

But for the whale being born with a rare atavistic throwback, it has an effectively nonfunctional lump of tissue hanging from it’s body. That lump of tissue has no function or adaptive benefit, and the whale lives in the open ocean, not in a beach area or other terrestrial-aquatic transition zone, so the whale has no use for such an appendage. Whales born with such appendages are no better at finding food, escaping predators, or finding a mate. They probably just impart some additional aquadynamic drag on the whale.

But an organims that lives in the right environment actually just might have an advantage. If the whale lived in a shallow marine environment and had to balance and support it’s body weight on land some times, in order to escape predators, or find food, then those appendages might actually be useful. The environment determines what, when, and where some particular attribute is adaptive.

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Wow, just wow. That is a really amazing set of videos. Thank you.

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