Hot-blooded crocodiles?

The animal can regulate shunting, increasing it during dives to send more hypoxic blood to the tissues, inducing a hypometabolic state---just the thing when you want to lurk underwater for a good long while.

Many of us see this as further evidence of intelligent design rather than a "weird,... sophisticated engine in low-tech chassis."
The crocodile needs a heart designed to allow it to dive and stay submerged without drowning. Would this not indicate that the presence of two aortas may have nothing to do with its ectothermic metabolism?
See also:
http://www.parentcompany.com/creation_explanation/cx7c.htm

Many of us see this as further evidence of intelligent design

— Jan

Conversely, it would be nice to have some doable test capable of demonstrating that crocodiles did NOT have endothermic ancestors, if in fact they did not. Otherwise, we're just comparing stories.

[PZ Myers=quote]...why do crocodiles have such fancy hearts.

I know PZ did not intend to invoke teleology, and were he to frame the question more carefully, he could dispense with the "why," but it is somewhat interesting (at least to me) that naturalists frequently use such language. Your garden-variety PBS or Discovery Channel programs on evolution are full of teleological characterizations of evolutionary processes. There seems to be something irresistable about explanations in terms of final cause.

Many of us see this as further evidence of intelligent design rather than a "weird, . . . sophisticated engine in low-tech chassis."

Perhaps our cognitive predispostition toward teleological constructions is a byproduct of a more general adaptation.

Conversely, it would be nice to have some doable test capable of demonstrating that crocodiles did NOT have endothermic ancestors, if in fact they did not. Otherwise, we're just comparing stories.

— Flint

I know PZ did not intend to invoke teleology, and were he to frame the question more carefully, he could dispense with the "why," but it is somewhat interesting (at least to me) that naturalists frequently use such language.

There seems to be something irresistable about explanations in terms of final cause

— Michael Finley

I do not know if your proposed test would be possible, attempting to demonstrate the positive [that they did have endothermic ancestors] and failing to do so would accomplish the same result, but from a different direction.

Failure to find evidence for something is NOT the same as finding evidence against. If in fact we can't determine even in principle that crocodiles' ancestors were exo or endothermic, we are telling stories. If we consider the plumbing of the crocodile strong enough evidence of endothermic ancestry, then let's just say so. If not, let's say what we'd need to find to support this hypothesis more fully.

— Flint

Any teleology in my comment is entirely in the mind of the reader. The word "why" is a useful part of the English language with a wide range of connotations; when I see it, I see no implication of purpose.

Re "finding positive evidence [for or against the position] is far better than saying that nothing has been found against, therefore it is true [which, upon reflection, would not be a valid conclusion]"

Unless that "nothing against" is in spite of there being lots of places where something "against" would be expected to be found if the hypothesis is wrong. Or would that be counted as positive evidence in that case?

Henry

Any teleology in my comment is entirely in the mind of the reader.

Though, to be fair, Finley does have a point that goes a little further than the fact that "why" can mean "how does it happen that..." as well as "for what purpose...". Given a biological structure, the genes for which show obvious conservation, "dogmatic darwinists" will usually at least tentatively assume that there is some selective pressure exerted on it - that it's performing some important function. If you ask "why are histone genes so highly conserved?" for instance, in a way you're asking "what critical function is met by these genes?" I think "evolutionists" often use "teleological shorthand" to convey exactly that.

As a biologist who works extensively with crocoilians I may suggest that the concept of an endothermic crocodile is not such a leap of logic at all.

1.First crocodilians genetically are closer to turtles and birds than snakes/lizards. They share much with birds, who shared much with dinosaurs. It is not a thought without merit to say crocodilians evolved an endothermic metabolism but that later it was selected against. Why?

2. Whereas the ancestors of crocodilians were primarily terrestrial predators modern crocodlians are, of course, waters edge predators. Endothermic metabolism is expensive to maintain whereas ectothermic metabolism would be a significant survival skill for an animal who can enjoy the protection of thermoregulation between aquatic and terrestrial environments.

So it is possible that a terrestrial crocodilian found endothermy profitable while after returning to an aquatic lifestyle found ectothermy an advantage. Natural selection simply modified the animal to adapt to a changing environment and new environmental niche for which they are perfect.

What's fascinating is which readers see teleology where it doesn't exist and isn't intended. These same readers see Intention wherever they look. So obvious they can't miss it.

— Flint

again, since teleology has raised its "ugly" head, i give you:

http://plato.stanford.edu/entries/teleology-biology/

just to help inform those who wonder what the argument against using teleological arguments in biology is about.

cheers

There is a single light of science, and to brighten it anywhere is to brighten it everywhere.
--Isaac Asimov

Would "dognatic darwinists" argue that the reason some gene is highly conserved is because lineages that failed to conserve it so highly aren't around anymore? If evolution is a giant game of trial and error and some genes don't change a single molecule in hundreds of millions of years, perhaps we can presume that any changes were exactly the sort of error natural selection corrects.

Russell: yes, it is often used to imply selection as a causative agent. I'm mostly innocent of that reflex, though, because my usual bias is that it is a developmental reason.

perhaps we can presume that any changes were exactly the sort of error natural selection corrects.

Once again an attempt is made to discredit those who reach a different conclusion than the majority here. Perhaps what you see as "silly" is actually something that you are unable to comprehend. You draw your conclusions on the basis of your scientific findings, non of which are conclusive. Obviously you are making a leap of 'faith', but it is what you believe. Let me ask you a question. It is likely that each of you have someone in your life that you love. Could you prove scientifically that you love the person? If not, does that mean that your love does not exist? Certainly you could give evidence of your love and others could conclude that you love, but to prove conclusively would not be possible. Would that mean that you are "silly" to say that you love someone? Life as we experience it here on Earth does not lend itself to being explained completely by scientific discovery. Certainly we can learn much about life and life processes, but to determine origin and purpose are outside of the realm of science. Scientist would do well to state this at the onset rather than be dogmatic and attempt to rule out any discussion or thought of a Designer or Creator who designs and creates with a purpose.

Would "dognatic darwinists" argue that the reason some gene is highly conserved is because lineages that failed to conserve it so highly aren't around anymore?

If evolution is a giant game of trial and error and some genes don't change a single molecule in hundreds of millions of years,

perhaps we can presume that any changes were exactly the sort of error natural selection corrects.

"Could you prove scientifically that you love the person?"

hmm, let's give it the old college effort shall we?

http://www.economist.com/printedition/displayStory.cfm?Story_ID=2424049

Perhaps what you see as "silly" is actually something that you are unable to comprehend.

Obviously you are making a leap of 'faith', but it is what you believe.

It is likely that each of you have someone in your life that you love. Could you prove scientifically that you love the person? If not, does that mean that your love does not exist?

Life as we experience it here on Earth does not lend itself to being explained completely by scientific discovery.

Certainly we can learn much about life and life processes, but to determine origin and purpose are outside of the realm of science.

Scientist would do well to state this at the onset rather than be dogmatic and attempt to rule out any discussion or thought of a Designer or Creator who designs and creates with a purpose.

Certainly we can learn much about life and life processes, but to determine origin and purpose are outside of the realm of science.

— Jan

First crocodilians genetically are closer to turtles and birds than snakes/lizards.

— Bioherper

Obviously you are making a leap of 'faith', but it is what you believe. ...No faith necessary with evidence.

Ahhhh but Flint

One is a rational faith at worst, while the other is completely irrational at best.

"There's probably some happy medium of evolutionary rate at least potentially"

how would you arrive at this "value", and how would it have any meaning?

"normal environmental change" is also a meaningless derivation. no such thing. selective pressures are EXTREMELY relative to the time and place (also remember they include a lot more than changes strictly due to environment as well).

the problem is that the relative level of variability in a given geographic region could (and does) vary widely over time; and periodic catastrophic events probably also play a large role, both on a local scale in a short geologic time frame (like hurricanes), and on a global scale wrt to large-scale catastrophic events (like ice ages).

moreover, as i mentioned, selective pressures don't just include physical processes of environment. often the most important selective pressures are biological.

cheers

Re "evolution of turtles. "

The webpage Amniota ( Mammals, reptiles (turtles, lizards, Sphenodon, crocodiles, birds) and their extinct relatives) shows turtles as branching off first from the Diapsida (the group containing lizards, crocodiles, and birds), but it shows a question mark indicating uncertainty as to the placement of the Testudine (turtle, tortoise, terrapin) clade.

Henry

Uber:

I agree. Absolute knowledge is a snare and a delusion; at some point we must play the odds as best we can assess them. But I like to give the benefit of the doubt, because it helps clarify that people do NOT have certainty, never can and never will. Most people WANT certainty, and most of them seem perfectly capable of pretending they have it. They call this pretense 'faith'. But it's certainly a different species of faith than you have.

Sir-Toejam:

I don't think I communicated with you very well. Let's say I speculate that most types of environmental change are fairly gradual (climate change, elevation change, etc.) and life forms have been able to track this rate of change without much difficulty. Mass extinctions, however, imply that there are at least some environmental changes too rapid for biological tracking to follow.

I think I could in principle arrive at a range of values for "ideal" evolutionary motion, at least as a computer model. No change would spell universal extinction sooner or later. Too much change would leave a good many niches for more conservative life forms to claim and defend. At least in my model. So I also speculate that life "experimented" with these various rates, especially early on, and those at the ends of the curve lost out. I'm not the only one to suspect that the ability to evolve has itself been the target of natural selection.

I don't disagree with anything you say.

"Could you prove scientifically that you love the person?"

I'm going to take some more time to think about it, but i believe you are a bit off here.

"Mass extinctions, however, imply that there are at least some environmental changes too rapid for biological tracking to follow."

indeed, it would also imply that evolutionary bottlenecks might play a larger role in the "evolution of evolution" than any fairly gradual effect.

I don't see how the outcome of a bottleneck would "average" meaningfully with the outcome of gradual change.

do you see what i am getting at?

you might be able to create a mathematical construct that would derive some sort of "average" but how meaningful would that actually be?

"Too much change would leave a good many niches for more conservative life forms to claim and defend. At least in my model. So I also speculate that life "experimented" with these various rates, especially early on, and those at the ends of the curve lost out."

no, in fact what we see is the exact opposite. Have you ever studied r vs. K selection?

the whole argument wouldn't even exist if there was some "average" evolutionary strategy and rate.

Can you see how different rates would be advantageous at different times from your own argument? It predicts divergence, not convergence.

Jan:

Are you the same Jan from whom I am still waiting for answers to questions I posted months ago? Your use of the singular "scientist" in the later post suggests so. If not, or if you forgot me, I happen to believe in design, and accept evolution.

Note that the article you linked is copyrighted 2003, and quotes Denton's 1986 work to support its promotion of incredulity toward common descent. Denton later accepted common descent, and even wrote a well-known book about it, "Nature's Destiny" (1998), in which he corrects his earlier misconceptions. So the article is at best irresponsible journalism, and at worst, willful misrepresentation. Sadly, nearly 100% of pseudoscientific anti-evolution articles published after 1998 make the same glaring omission. In case you forgot, God doesn't like it when people bear false witness.

Denton's acceptance of common descent does not make it necessarily true, of course, but multiple lines of independence evidence do. The authors of your article misrepresent that too. And they reference Patterson liberally. I haven't checked whether they quoted him out of context, but that too is standard practice for pseudoscientific anti-evolutionists. So it behooves you to be as skeptical of such articles as you are incredulous of evolution (or pretend to be).

Once again an attempt is made to discredit those who reach a different conclusion than the majority here. Perhaps what you see as "silly" is actually something that you are unable to comprehend.

— Jan

You draw your conclusions on the basis of your scientific findings, non of which are conclusive. Obviously you are making a leap of 'faith', but it is what you believe.

— Jan

Let me ask you a question. It is likely that each of you have someone in your life that you love. Could you prove scientifically that you love the person? If not, does that mean that your love does not exist?

— Jan

Certainly you could give evidence of your love and others could conclude that you love, but to prove conclusively would not be possible. Would that mean that you are "silly" to say that you love someone? Life as we experience it here on Earth does not lend itself to being explained completely by scientific discovery.

— Jan

Certainly we can learn much about life and life processes, but to determine origin and purpose are outside of the realm of science.

— Jan

Scientist would do well to state this at the onset rather than be dogmatic and attempt to rule out any discussion or thought of a Designer or Creator who designs and creates with a purpose.

— Jan

(On Sir_Toejam's comment about r vs K selection in #25790 above)

I was under the impression that r vs K selection is about reproductive rates, not mutation rates. Basically a tradeoff between producing as many offspring as possible vs. producing a few offspring with low mortality rates.

While "optimal" mutation rates could be different in "r" situations than in "K" situations this would not appear to be immediately obvious.

See the galloping crocs here!

http://www.flmnh.ufl.edu/natsci/herpetology/brittoncrocs/

Read somewhere that leatherback turtles are endothermic - markedly so. Perhaps a diet of jellies is just the thing. Could one tell they're endothermic (if indeed they are) from dissecting a dead one?

hmm, i must admit i no longer have the access i would like to the primary literature that i used to when i was in academia, I seem to recall the argument had been extended to discussions of evolutionary strategies as well as reproductive ones (especially in organisms with short reproductive cycles).

>>"While "optimal" mutation rates could be different in "r" situations than in "K" situations this would not appear to be immediately obvious."
<<

why not? any strategy that ends up increasing fitness in a particular circumstance would be favored. seems to extend naturally in my mind.

in times of large disturbance, organisms favored to evolve quickly, either via rapid mutation rates or rapid reproduction rates would be favored. either would result in significantly lower populations relative to what would occur in more stable conditions by orgnanisms exhibiting lower mutation rates or more "K" selected reproduction rates.

even if we completely eliminate anything but physical disturbance as a selective force, there have been periods and places of relatively constant gradual change in environment, and periods of relatively fast change (let's exclude the bottlenecks for now). so there is room for both mutation strategies to have continued.

IMO, you can see how this naturally extends from the much smaller case examples that are often used to explain r vs. K reproductive strategies. typically, the change in species composition in stable forest clearings are commonly used. In its terminal mode, dense stands of "K" selected trees dominate, but when a tree falls, creating a disturbance and opening up space, we see succesful invasions of r selected species, typically giving way over time to the trees again (barring other outside disturbances, of course).

comparing the analogy, you can see why i would find an "average value" of reproductive strategies between the r and K selected species to be of dubious value.

Am i being at all clear?

cheers

[hmm. sorry if this ends up being posted multiple times. I think the site needs a bit of work on the code or server side.]

hmm, i must admit i no longer have the access i would like to the primary literature that i used to when i was in academia, I seem to recall the argument had been extended to discussions of evolutionary strategies as well as reproductive ones (especially in organisms with short reproductive cycles).

>>"While "optimal" mutation rates could be different in "r" situations than in "K" situations this would not appear to be immediately obvious."
<<

why not? any strategy that ends up increasing fitness in a particular circumstance would be favored. seems to extend naturally in my mind.

in times of large disturbance, organisms favored to evolve quickly, either via rapid mutation rates or rapid reproduction rates would be favored. either would result in significantly lower populations relative to what would occur in more stable conditions by orgnanisms exhibiting lower mutation rates or more "K" selected reproduction rates.

even if we completely eliminate anything but physical disturbance as a selective force, there have been periods and places of relatively constant gradual change in environment, and periods of relatively fast change (let's exclude the bottlenecks for now). so there is room for both mutation strategies to have continued.

IMO, you can see how this naturally extends from the much smaller case examples that are often used to explain r vs. K reproductive strategies. typically, the change in species composition in stable forest clearings are commonly used. In its terminal mode, dense stands of "K" selected trees dominate, but when a tree falls, creating a disturbance and opening up space, we see succesful invasions of r selected species, typically giving way over time to the trees again (barring other outside disturbances, of course).

comparing the analogy, you can see why i would find an "average value" of reproductive strategies between the r and K selected species to be of dubious value.

Am i being at all clear?

cheers

Textbooks portray turtles as the most primitive group of egg-laying animals (amniotes) in existence and extol their virtues as model organisms for primitive amniote organization and physiology. In their report published on page 998 of this issue, Hedges and Poling (1) present an exhaustive analysis of turtle relationships on the basis of DNA data. Their results, which support other recent analyses of protein (2) and DNA (3, 4) sequences, indicate that instead of being related to the anapsid root of the reptile evolutionary tree, turtles nest in the tree crown, within Diapsida. These molecular data thus are partially congruent with morphological characters that also support diapsid (5), rather than anapsid (6), turtle relationships. However, the molecular data conflict with paleontological data as to where exactly turtles fit within diapsids. The DNA data also support a highly controversial relationship of the Tuatara, and it will be a challenge not only to paleontologists, as suggested by Hedges and Poling, but also to molecular systematists to resolve these conflicts. ... Morphological data (5, 12) place the turtles as sister-group of the Sauropterygia, both nested at the base of the lepidosauromorph lineage. This contrasts with all available molecular data, which put turtles on the archosauromorph branch. Although the placement of turtles within Diapsida is the most parsimonious solution on the basis of all data at hand, the statistical support for both lepidosauromorph and archosauromorph affinities of turtles, on the basis of anatomical and molecular data, respectively, may be relatively weak in some cases. This reflects a high degree of independent evolution of morphological similarity (convergence) within anapsid and diapsid reptiles on the one hand, and the impact of a long separate evolution of the turtle branch on molecular characters on the other. However, an as yet unpublished morphological data set (13) places the Sauropterygia at the base of the archosauromorph lineage. The effect of inclusion of turtles into this data set has not yet been explored, but if Sauropterygia exert the same pull as they previously did (5, 11), turtles might end up as archosauromorphs on the basis of morphological characters also.

Could you prove scientifically that you love the person?

— jan

Scientist would do well to state this at the onset rather than be dogmatic and attempt to rule out any discussion or thought of a Designer or Creator who designs and creates with a purpose.

— jan

Thank you, wildlifer.

Jan -

Any features an organism has you can say was intended by an intelligent designer that had the ability to obtain what we observe. This works, because you bury the observations you seek to explain in there existing a completely hypothetical designer with no independent evidence having the goal and ability to create your observations. This can be done with literally anything, from volcanoes to vertebrate eyes, and is completely useless. It explains nothing. The only constraints on the potential intentions and abilities of an assumed hypothetical designer are artificial ones you might put on it - such as religious doctrine.

For further discussion of this concept, see Elliot Sober's paper:

Intelligent Design and Probablity Reasoning.

http://philosophy.wisc.edu/sober/ID&PRword.PDF#search='Intelligent%20Design%20and%20probability%20reasoning'

Sir Toejam,

I'm still not sure if we are communicating. I see what you are driving at, I think, but it wasn't what I was trying to say. Consider absurd extremes: A lineage unable to evolve at all, and another, uh, perhaps "lineage" is the wrong term, where offspring differ from parent so completely that their ability to mate even with siblings is unlikely. I suggest that neither of these extremes would be around for more than a few generations. Instead, what I would expect to be selected for is the ability to evolve reasonably quickly, "reasonably" being considered as capable of adapting to periods of relatively fast change (excluding the bottlenecks).

Let me try a different tack. We see hox genes conserved to a remarkable degree (as an example). Surely (unless you are a closet creationist) these genes in all their complexity didn't appear POOF all at once and nothing first. They must themselves be the product of selection from a broader range of precursors, most of which were NOT conserved. But anyway, back to the crocodiles...

"Let me try a different tack. We see hox genes conserved to a remarkable degree (as an example). Surely (unless you are a closet creationist) these genes in all their complexity didn't appear POOF all at once and nothing first. They must themselves be the product of selection from a broader range of precursors, most of which were NOT conserved. But anyway, back to the crocodiles . . . "

okeedokee. assuming crossed wires... wiping the slate then. let's take this step by step.

so you are arguing that the conservation of specific gene sequences is related to a previous state where non conservation was far more common, is this correct?

er wait. you have a point. let's take this offline and get back to the crocs. email me if you would like to continue.

cheers

Perhaps our cognitive predispostition toward teleological constructions is a byproduct of a more general adaptation.

"So it is possible that a terrestrial crocodilian found endothermy profitable while after returning to an aquatic lifestyle found ectothermy an advantage. Natural selection simply modified the animal to adapt to a changing environment and new environmental niche for which they are perfect". Herperbio, Are crocodiles perfect for their environmental niche? Observing their heart, far from it. It is a patchwork of fixes on former corrections. What other hotblooded animal remade itself to ectothermism when returning to water? Is echtotermism profitable for an animal with long periods of inactivity with sudden burst of intense activity?