Did We Have "Reptilian" Ancestors?

Science

(John Harshman) #121

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.


(Robert Byers) #122

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.


(Timothy Horton) #123

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.


(Timothy Horton) #124

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:


(Herculean Skeptic) #125

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?


(Timothy Horton) #126

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.


(Greg) #127

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.


(Mikkel R.) #128

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.


(S. Joshua Swamidass) #129

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


(Timothy Horton) #130

You’re not. Behe’s claims are trash pseudo-science where he cherry-picks data points and ignores the large amount of evidence which contradicts his assertions. Science has known for over a century evolution works by modifying existing structures. Older structures “break” or are co-opted for new functions when the environment changes and the older functions no longer provide a selection advantage. This is not news but the way Behe spins it makes it seem like some grand discovery. Behe is the worst kind of Liar For Jesus, an educated man who deliberately misleads the lay public in order to push his religious agenda.


(John Harshman) #131

Think of it this way. The Texas sharpshooter is a fine analogy. The sharpshooter shoots at the side of a barn, hits some spot, and draws a target around that spot. The probability of hitting that target (i.e., anywhere on the side of the barn) the first time is large. But the probability of hitting that same target on the next shot is small. Getting some sort of leg the first time is not so improbable, especially since the animal is starting out with a fin that has all the right bones. But the same leg a second time, from scratch? Unlikely.

Note also that the leg is not a new organ. It comes from a fin, and that fin itself has a long prior history, starting (apparently) as a simple fold in the body wall.


(John Harshman) #132

That’s not fossil evidence. It’s just the most parsimonious inference from a phylogenetic analysis, assuming that loss and regain are equally likely. A lot of biologists think that multiple losses are more plausible than multiple (though fewer) re-evolutions.


(Mikkel R.) #133

I really don’t think Behe is knowingly telling falsehoods, and it isn’t necessary to invoke that kind of explanation for why a man of his education says wrong things. Some times people can really just be genuinely mistaken, or have been misled (or even have misled themselves for reasons of well-known cognitive biases that affect us all from time to time), for all sorts of reasons that have nothing to do with intentional malice or hucksterism.


(Timothy Horton) #134

I respectfully disagree. DI stooges like Behe, Meyer, Axe have been corrected by other scientists way too many times to not know what they are pushing is pseudo-science garbage. I’ve never seen any of them address and correct their grievous errors. To me the biggest tell is their refusal to publish in the primary scientific literature and instead write popular press books. If they honestly thought they were doing good science why the constant end runs around professional vetting?


(Herculean Skeptic) #135

Hey Tim, don’t people here know people who could see this get done? Can people (here and elsewhere) offer to help so that a conversation (rather than no conversation, like now) ensues? It seems to me that the “stooge” and “pseudo-science garbage” comments make it much more difficult to progress. There’s so much pride among professionals in this arena that it’s easy to see how a bad situation would get worse and worse. Eventually, someone is going to have to step up and invite them in. Can this be done, or are we simply to expect endless mudslinging until the end of time? Or is it your contention that their position is hopeless and they are simply pandering to a different, uninformed audience and, as such, they do not care about peer review?

If the latter is the case, then we’re all still doomed to revisit these conversations again and again, because they are winning the war of words with the public. They are articulating a message that the public understands. In that case, speaking poorly of the authors and their work will only encourage the public to disengage more with the science community. The only way to win this, or even just improve it so that everyone can see the entire landscape at the same time, is to engage with them, not against them.

Really, the issue is not one of correctness or incorrectness, it is one of perception.


(Timothy Horton) #136

But the “message” is based on provable lies. I see no point in coddling proven liars who are out to undermine scientific literacy in my country. I’ll actively fight them as long as I am able.

Remember British PM Neville Chamberlain returning from Germany in 1938 with his “peace is at hand” declaration? How did that work out?

That’s exactly what I think they are doing. Lots of other science professionals think so too.


(Herculean Skeptic) #137

Thanks John, for your patience in explaining. I don’t mean to belabor in order to argue, but I’m still struggling with this question that I have regarding parsimony and its role in an evolving species. What I’m gathering from what you have said is that, when one observes an organism that has a function that is not fully developed, that the assumption (based upon parsimony) is that this function is vestigial or the recurrence of a function that had formed earlier in the historical lineage of that organism. Is this basically correct?

If so, it seems to me that every function that formed over time (legs, fins, organs, etc.) would also fall under that same rule of parsimony. If a new function or feature rarely forms, and every feature or function was once new, then it seems that you would always be looking for new functions, because every function formed newly, once at least, in the past. Let’s say that the earliest common species for several classes of animals was a worm-like animal that had some sort of skeleton. (Maybe a very simple snake would be a better example.)

Since, from that snake, creatures with limbs, complete with upper and lower legs, knee joints, feet, toes, tarsals, etc., would have descended, it seems like we should also be looking for (and expecting to see) this process continuing today. As you said, this does not occur instantaneously, but rather over a long period of time. But if parsimony leads us to believe that new functions (features) are rarely added, we must have overcome that rule many times over.

That it is easier to recycle an existing function (feature) into something novel makes sense. That parsimony would apply also makes sense. That the diversity of function that we see, much of which was once novel, overcame that obstacle (parsimony) does not make sense to me.


#138

because we had a discussion about whales first. so i want to stay in focus.


(Herculean Skeptic) #139

There’s nothing about “coddling” in the peer review process. The point is that there’s two ways to fight. One is to work to prevent their message, and the other is to work to get their message through the peer review process. If the information presented does not stand up to scrutiny, they need to return to the computer and work on it.

Chamberlain lied. And you will know the truth, and the truth will set you free. This is always the case. The truth is self-evident. I think you are missing the point. By trying to assist them to get their works properly reviewed, it seems that one of two things will happen.

  1. They will have been welcomed to the process publicly and will avoid participating, or,
  2. They will participate in the process and their works will be reviewed.

It seems like your goals would be met in either case, and that you would not suffer in terms of public opinion.


(Timothy Horton) #140

The DI stooges know it too. That’s why they don’t submit their garbage fro proper peer review. They know it will never pass muster.

It’s not up to me or anyone in science to get the DI’s garbage through peer review. That is THEIR job. All we can do is call them on it when they refuse to follow proper scientific processes.

Do you honestly think the DI is interested in bringing their nonsense up to proper scientific standards?