quote:Mammary glands are the organs that, in mammals, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and give mammals their name. The mammary glands of domestic mammals containing more than two breasts are called dugs.
This is logical as sweat could be licked by young, and this would provide liquids and result in stimulation to sweat more to fulfill the purpose of sweating. A feedback cycle ensues.
Laugh!
One should always be careful of laughing first and thinking second. Especially when what you posted does not challenge or even address the issue that Mr. Jack raised for how the molecules work.
The origin and evolution of lactation, Anthony V Capuco and R Michael Akers
Yep, I just googled it and found the source. They go on to discuss the evolutionary history of lactation and where it fits in the tree of descent from common ancestors:
quote:Lactation appears to be an ancient reproductive feature that pre-dates the origin of mammals. A cogent theory for the evolution of the mammary gland and lactation has been provided by Olav Oftedal [1]. The features of current mammals were gradually accrued through radiations of synapsid ancestors, and the mammary gland is hypothesized to have evolved from apocrine-like glands associated with hair follicles (Figure 1). Oftedal suggests that these glands evolved from providing primarily moisture and antimicrobials to parchment-shelled eggs to the role of supplying nutrients for offspring. Fossil evidence indicates that some of the therapsids and the mammalia-formes, which were present during the Triassic period more than 200 million years ago, produced a nutrient-rich milk-like secretion.
It's just classic creationists, quote mining from the introduction of a paper in which the authors attempt to define the problem that they wish to discuss. The structure of the paper is:
Yes, the fact that original ideas may not be correct in details, and that later evidence and increased knowledge can result in revisions of such ideas is an integral basal concept in science that seems to escape some people.
The last laugh is that evidence of lactation evolving shows added information
Hi Kaichos Man
Message 56: You, and Mr Jack, and RADZ, fail to see the point of the humour. It's not that Darwin got it wrong. It's that this scientist decided to make an editorial point about the theory and used, as it turned out, a very poor example to do so.
I don't know if you're old enough to have been exposed to Monty Python, but it's in the same vein as:
"They said I was mad to build a castle in a swamp, but I built it anyway- just to show them!...it sank into the swamp...
Curiously, Monty Python does not qualify as biological information to support a position, which leaves you looking like the Black Knight.
Actually, I find it quite amusing that all you can do is make a poor attempt at mockery rather than present even half of an argument or evidence that actually would support your position. That was the implication of my subtitle - in case you missed it - he who laughs first is not going to be the one who laughs last, and in this case it appears you have egg on your face.
Oh dear. He's got the proto-mammal suckling an egg on her hair follicle.
Curiously, you don't seem to be aware how permeable egg shells are, especially non-avian eggs. The mammal egg shell is just a semi-permeable membrane during pregnancy. The eggs of monotremes are more like reptile and amphibian eggs - also semi-permeable membranes.
quote:... The eggs develop in utero for about 28 days with only about 10 days of external incubation (in contrast to a chicken egg, which spends about 1 day in tract and 21 days externally).[37] After laying her eggs, the female curls around them. The incubation period is separated into three parts. In the first, the embryo has no functional organs and relies on the yolk sac for sustenance. The yolk is absorbed by the developing young.[47] During the second, the digits develop, and in the last, the egg tooth appears.[48]
The newly hatched young are vulnerable, blind, and hairless, and are fed by the mother's milk. Although possessing mammary glands, the Platypus lacks teats. Instead, milk is released through pores in the skin. There are grooves on her abdomen that form pools of milk, allowing the young to lap it up.[3][36] After they hatch, the offspring are suckled for three to four months. ...
Gosh, there's those skin pores becoming mammary glands used for lactation again ... and amazingly these pores are inside the brood pouch for these animals. Who could have predicted that!
"Appears to be". Uh-huh.
Yes, that is what the evidence shows: mammals have mammary glands, marsupials have mammary glands, monotremes have mammary glands. The evidence at the cellular level shows that these are of similar development, developed from the same basic cells, rather that convergent evolution with other types of cells being adapted for this purpose. The evidence of the molecules (as pointed out by Mr.Jack in Message 40 and unrefuted by you) is that the same molecules are adapted to produce the lactose. The article also states that "disaccharide lactose (galactose β1—4 glucose) is contained in all milks, except for those of some marine mammals." This argues for common ancestry of all these organisms, and thus one can logically conclude from the evidence that "Lactation appears to be an ancient reproductive feature that pre-dates the origin of mammals."
Oh dear, an hypothesis.
Yes, an explanation for the evidence. In science you start with evidence, and then form a logical hypothesis based on the evidence, and then move on to testing that hypothesis. An hypothesis that has been tested is called a theory, so in this instance he is clearly stating that this is an untested explanation of the facts at this time.
Oh good. Cogent. We can relax. Cogency alert! Let's hope it's cogent.
-adjective Appealing to the intellect or powers of reasoning; convincing: a cogent argument. See Synonyms at valid.
(American Heritage Dictionary, 2009)
In other words logical and supported by evidence, rather than an ad hoc comment with little real information. Unfortunately, I have not been able to find an example of a cogent comment in your posts to use here, as they seem to be information free. Instead I have to look at posts like Message 44 for a good example:
A man who didn't know about genes, didn't know about the molecular basis for tissue differentiation, didn't know about the existence of control genes, or how they work, didn't know about the chemicals involved in lactation - and so ad nauseum - didn't get his ideas about the details right? I'm staggered.
Notice the reference to evidence and the things that we now know about evolution in general and lactation in specific.
Amazing! 200 million year old fossils, and not only can they tell that they secreted stuff, they even know what was in it!
Yes, it is amazing what you can deduct from the evidence, rather than just pretend to know. For instance, the same article goes on to discuss just the 200 million year old fossil evidence that supports this conclusion:
quote:The evolution of the casein family of milk proteins in particular would provide calcium, phosphate and protein to hatchlings. Fossil records suggest that caseins were present during the Triassic, because the extensive bone and tooth development evident in the relevant species at stages before independent feeding would have required delivery of ample calcium. Given this evolutionary scenario, the composition of mammary secretions during early lactation in monotremes and marsupials is likely to be similar to that of the primitive milk of mammalian predecessors
Bold for emphasis.
Hmm. You know, I'm starting to like Darwin's version more and more...
Curiously, reality in general, and lactation in particular, are completely unaffected by your opinion, or your likes and dislikes.
So Darwin was right? And the evolutionist scientist I quoted was wrong?
They could both be wrong.
Darwin could be wrong about the evolutionary beginning of the mammary gland ("evolved from cutaneous glands that were contained within the brood pouches in which some fish and other marine species keep their eggs") rather than later in the process of descent from common ancestors (ie within a subclade of tetrapods that were ancestors to mammalia), while being essentially correct about it being developed from skin glands (of which we now know there are several types) and from the first appearance inside brood pouches (although the evidence for this is not clear).
Likewise the scientist could be wrong about it not evolving inside a brood pouch (again the evidence is unclear on this), but being essentially correct that the mammary gland did not evolve from a pouch as a whole.
It also does not matter who is right or that either is wrong about this specific issue, as the fact remains that lactation evolved as a means of improving the survivability of the young, and thus would be selected, nor does this alter the fact that the modification of molecules to be able to produce the chemicals in milk show the presence of information not existing in previous ancestral fossils (teeth and bone development) or in other species that have descended from more ancient common ancestors.
In science it is not important WHO is correct, as WHAT is correct is the important part. What is correct is that lactation has evolved from chemical modification and adaptation of skin glands.
Thus when you focus on who is wrong you are not addressing the issue of what is correct. What is correct is that information has been added.
What fossil records "suggest" is that caseins were present.
Curiously, once again you display a flair for disingenuous clutching at straws that turn into smoke when one looks further:
quote:Casein (from Latin caseus "cheese") is the predominant phosphoprotein (αS1, αS2, β, κ) that accounts for nearly 80% of proteins in cow milk and cheese.
So whether it was developed enough to be called "milk" is irrelevant to the fact that the primary ingredient in milks in this day and age is casein, and that this protein was not available for the growth and development of young prior to this, as demonstrated by the fossil evidence.
That they were present in mammary secretion is pure conjecture, or to use your own words:
No, not pure conjecture, pure conjecture would not be based on evidence.
or to use your own words:
an untested explanation of the facts at this time
And because it explains the known evidence it is not pure conjecture.
But don't worry. It'll soon turn up in a biology textbook near you as "fact".
THAT is pure conjecture. Notice the difference? Lactation supported by evidence, your assertion supported by nothing but your opinion.
Curiously, reality in general, and lactation in particular, are completely unaffected by your opinion, or your likes and dislikes.
Yeah. Ain't it the truth.
And amusingly, you keep eagerly demonstrating the truth that your opinion is worthless in discussing reality.
We still see that the evidence shows that lactation evolved in the mammalalia lineage, and that prior to this evolution casein was not evident in the growth and development of young.
Thus lactation provided a benefit from modification of molecules and adaptation of existing elements for a new use. This means that either (a) information was added to the genome or (b) the concept of "information" is useless in describing what can and cannot occur through evolution.
The thesis of this thread is thereby demonstrated.
But disproving that there can be no net increase in information does nothing significant to disprove evolution as a whole.
The IDist argument about increase in information is born from the old creationist argument about changes in species only showing loss and decay from the original created "kinds" due to the introduction of disease and death after the "fall" -- ie a purely religious origin -- taken as the basis for a pseudoscientific position (ie pure conjecture). The argument comes full circle when religious FUNDIE/s (fundamentalists under numerous delusions involving evolution) take the ID position as a new gospel.
The fact that there is so much evidence of loss and recovery that it becomes virtually self-evident that either gain in information does occur, or that the concept of information used by the IDcreationists is useless in predicting any restriction on evolution.
Polyploidy in plants, on the the other hand, occurs very often.
And result in virtually instant speciation. One known example in mammals is (not really a) rat in Argentina:
quote:Polyploidy is much rarer in animals. It is found in some insects, fishes, amphibians, and reptiles. Until recently, no polyploid mammal was known. However, the 23 September 1999 issue of Nature reports that a polyploid (tetraploid; 4n = 102) rat has been found in Argentina.
Re: The last laugh is that evidence of lactation evolving shows added information
Hi again Kaichos Man, finally an argument?
Because faith hangs on. And make no mistake about it, atheism is a faith.
I suggest you read both my signature and Pseudoskepticism and logic before you go making unfounded assumptions. The topic is closed now, so you won't have a chance to provide your input. If you are lazy you can read my summary of the topic Message 562. Let's not try to pretend that atheists are your only adversaries in this debate.
RADZ, let's discuss reality.
Indeed: reality as in the many types of faith that have no argument/s with evolution, and reality as in knowledge supported by the evidence.
1. The creatures were too young to feed themselves.
Which is NOT what the article said, so this argument is based on a misrepresentation, and is just a straw man, rather than reality.
In deciding whether a creature is old enough to feed itself, size is not an issue. The smallest herbivor can graze, the smallest carnivore can hunt small prey. The main consideration (particularly in a fossil) must be the development of teeth and bones.
The main consideration is the level of development of teeth and bones in comparison to earlier fossils and to fossils of other closely related (similar homologies) organisms living at the same time, it isn't just some arbitrary decision. The article points to one place in the fossil record:
This is evident from the article, as it points out that at this one point in time the development of teeth and bones in this group of organisms was faster the previous fossils or related fossils -- they apply to any organisms in the cynodontia clade and not to organisms outside the cynodontia clade. They point to one place in the fossil record in one lineage of fossils to identify where this happens.
... The smallest herbivor can graze, the smallest carnivore can hunt small prey. ...
But not enough to grow at the rate that these animals grew (bone size). In many mammals today, they are not able to support their own life by self feeding when they are deprived of their mother.
... Given that these creatures had well-developed teeth and bones, why did the scientists decide they were too young to feed themselves?
This question is based on your misreading of the article. Let's go back and read again what the article said:
quote:The evolution of the casein family of milk proteins in particular would provide calcium, phosphate and protein to hatchlings. Fossil records suggest that caseins were present during the Triassic, because the extensive bone and tooth development evident in the relevant species at stages before independent feeding would have required delivery of ample calcium. Given this evolutionary scenario, the composition of mammary secretions during early lactation in monotremes and marsupials is likely to be similar to that of the primitive milk of mammalian predecessors
(bold for emphasis again).
It's not that they are "too young to feed themselves" but that the could not eat enough, feeding on their own, to grow at the rate of growth that is observed in the fossil record, in this lineage, at this point in time.
2. The bone and tooth structures suggested an abundance of calcium.
The bones and teeth in these fossils show the accumulation of calcium at an increased rate compared to other fossils which indicates a new source of calcium is used, one that is not used by organisms that are not in the cynodontia clade.
As a minor diversion involving the cynodontia clade, we'll review a previous (mistaken) comment of yours (Message 66):
"disaccharide lactose (galactose 1—4 glucose) is contained in all milks, except for those of some marine mammals." This argues for common ancestry of all these organisms
And must therefore, logically, argue against common ancestry for those marine mammals.
This is poor logic at best, as this would only be true if this occurred at the same time as the evolution of lactation. The marine mammals are still within the cynodontia clade, and membership in the clade is based on common ancestry, which is based on having homologous traits, one of which is the production of certain proteins. Any one of these homologous traits can be lost or further modified by later evolution, and the cladistics of marine mammals show that they diverged from mammals much more recently than the beginning evidence of milk in the fossil record. These mammals are also still characterized by being milk producing and milk feeding organisms, just ones without this one protein.
Marine mammals are also still members of the therapsid clade, the mammalia clade and the eutheria clade/s. If you want to discuss/learn more about clades I suggest Clades and Kinds.
Well developed teeth and bones certainly suggest an abundant supply of calcium, but why does it need to be in the form of caseins? A lot of eggs are primarily composed of calcium, after all. If calcium can be used to build the egg, why not the teeth and bones of the creature inside? Baby crocodiles don't recieve caseins from mammary secretion. Do they exhibit underdeveloped teeth and bones?
They don't exhibit the rate of growth of mammals. Even if the egg shells are consumed rather than abandoned, there is only so much calcium in the egg shells, certainly no enough to support months of growth.
3. The abundance of calcium suggested the presence of caseins.
The increased rate of growth suggests a new source of calcium not present in previous ancestral organisms or in later organisms that are not members or descendants members of the cynodontia clade.
4. The presence of caseins suggested mammary secretion.
Which are casein rich secretions. All members of the cynodontia clade show patterns of increased rates of growth of young in excess of the rate of growth for non-cynodontia clade members, and all living mammals show that this is due to the presence of caseins in milk. Further, the rate of growth in modern mammals is similar to that of the early fossils.
Now you may ask why trained scientists would draw the far-fetched conclusion of "mammary secretion" based on such dubious evidence.
Oops. So much for argument not based on opinion. You have failed to demonstrate that the logical conclusions supported by the evidence are "far-fetched" in any way, and instead just asserted it as fact. This, of course is a well-known result of cognitive dissonance:
Some common first attempts to resolve this conflict involve denial of the evidence, ridiculing the concept, or claiming there is some vast conspiracy involved. People mock what they have trouble understanding, or make up fantasy scenarios to explain (to themselves) why other people could argue for the contradictory evidence, or even (shudder) find the contradictory evidence more compelling than your opinion.
But to do so is to fail to understand the evolutionary paradigm.
The theory must be supported and explained. Lactation exists, therefore it must have evolved. It is the duty of every scientist to explain how evolution took place.
That's why in evolution, unlike any other field of science, alternative hypotheses are discarded solely on the basis that they don't support the theory. The theory validates the facts, not vice versa. If the facts are at variance to the theory, then they can't be facts. There is no better example of this than the 110 years during which the ToE was soundly falsified by the fossil record, until Gould and Eldredge came up with the theory of Punctuated Equilibrium.
Sadly for you, once again we see that your opinion of how science works is amusingly at odds with the reality of how science works. All science looks for answers to how things work the way they do, and when something is not explained they acknowledge that it is unexplained. Because {X} is not explained does not mean that theory {Y} is false, it just implies that either (a) the evidence, (b) the application of the theory or (c) the explanation of the current theory is incomplete.
Fascinatingly, theories in science -- in all sciences - are only discarded when they are falsified, not when there is evidence that is not explained. This is especially so of theories that explain piles of known evidence.
The theory must be supported and explained. Lactation exists, therefore it must have evolved. It is the duty of every scientist to explain how evolution took place.
That's why in evolution, unlike any other field of science, alternative hypotheses are discarded solely on the basis that they don't support the theory. The theory validates the facts, not vice versa. If the facts are at variance to the theory, then they can't be facts. There is no better example of this than the 110 years during which the ToE was soundly falsified by the fossil record, until Gould and Eldredge came up with the theory of Punctuated Equilibrium.
Whether you agree with punctuated equilibrium or not isn't the point. Why wasn't the theory dropped during those 110 years?
Amusingly science does not work like creationism, starting from a premise and then searching for evidence to support it while discarding contradictory evidence along the way.
Curiously, punctuated equilibrium was also suggested by Darwin, as he talked about different rates of evolution. Fascinatingly there is bountiful evidence of gradualistic evolution as well as rapid evolution: the evidence is that the rates of evolution can change in different circumstances. If you want to discuss this topic it is better suited to the ongoing discussion on Stasis and Evolution.
Amusingly another one of the early ways to deal with cognitive dissonance is to try to change the subject away from the issue where dissonance is getting bothersome. The whole issue of punk eek has absolutely nothing to do with the evolution of lactation.
And thus, at the end of the day, we still have (1) evidence that lactation began ~200 million years ago in the basal group for the cynodontia clade, (2) evidence that lactation exists in all descendents within the cynodontia clade, albeit in later modified form in marine mammals, (3) lactation does not exist outside the cynodontia clade, either before cynodontia or in other clades, and (4) this process results in rapid growth of the young, a selectable evolutionary benefit, and finally (5) the information for this process is not evident outside the cynodontia clade. Again, if you want to discuss/learn more about clades I suggest Clades and Kinds.
Lactation demonstrates a new feature in members of the Cynodontia Clade that evolved through the adaptation of an existing feature to a new use. Either this adds "information" to the genome, or the concept of "information" is useless for discussing the relative possibility of new features evolving.
Suffice it to say that while not all evolutionists are atheists, it's a safe bet that all atheists are evolutionists.
Nope. False logic again. Rather atheism and sciences are not necessarily related.
Further, if we look at the religious people that find evolution objectionable we see that they are subsets of some religions, particularly fundamentalist sects, while other sects of the same basic religion have no argument with evolution. Logically this says that the disagreement lies in the fundamentalist camp/s, and not in the rest of the population.
We know little about cynodontia's diet (that isn't conjecture, no matter how reasonable) and even less about their eating capacity and metabolism. All we know is that the juveniles were well supplied with calcium. Comparison with earlier "relatives" or contemporary homologs is not valid, as we see wide variety in diets/eating capacities/metabolisms in closely related species today.
What we see is a more rapid rate of growth in the cynodontia clade consistently from that point to the present. Outside that clade we do not see this rate of growth.
Why? It's very simple logic. If the presence of disaccharide lactose argues for common ancestory, then its absence must, ipso facto, argue against it. Therefore if the author wanted to argue for common ancestory, he chose a pretty weak premise on which to do so.
I understand that it is simple logic, I'm just pointing out that it is false to assume that the trait was not lost long after the original gain, especially when there are (a) numerous other homologies that unite marine mammals with terrestrial ones, (b) other homologies with terrestrial mammals that marine mammals have lost, (c) losing traits is not uncommon in evolution, and (d) they still posses mammary glands and feed their young milk, just milk without this one protein -- the other milk products are homologous with other mammals.
Are you really trying to argue that marine mammals are not related to other mammals based on one milk protein? I have a nephew who was not able to digest mother's milk - does that make him not-mammal?
The 110 years during which evolutionists retained the ToE while knowing that the fossil record comprehensively contradicted the theory is probably history's best example of cognitive dissonance.
Again, this is a falsehood: Darwin talked about punk-eek. You must have missed it on the Stasis and Evolution thread where Modulus posted chapter and verse (Message 36):
Chapter 10, On the Origin of Species (first ed):
quote:Species of different genera and classes have not changed at the same rate, or in the same degree. In the oldest tertiary beds a few living shells may still be found in the midst of a multitude of extinct forms. Falconer has given a striking instance of a similar fact, in an existing crocodile associated with many strange and lost mammals and reptiles in the sub-Himalayan deposits. The Silurian Lingula differs but little from the living species of this genus; whereas most of the other Silurian Molluscs and all the Crustaceans have changed greatly. The productions of the land seem to change at a quicker rate than those of the sea, of which a striking instance has lately been observed in Switzerland.
and
Chapter 15, same (though I think this particular quote was added in a later edition):
quote:Only a small portion of the world has been geologically explored. Only organic beings of certain classes can be preserved in a fossil condition, at least in any great number. Many species when once formed never undergo any further change but become extinct without leaving modified descendants; and the periods during which species have undergone modification, though long as measured by years, have probably been short in comparison with the periods during which they retained the same form. It is the dominant and widely ranging species which vary most frequently and vary most, and varieties are often at first local--both causes rendering the discovery of intermediate links in any one formation less likely. Local varieties will not spread into other and distant regions until they are considerably modified and improved; and when they have spread, and are discovered in a geological formation, they appear as if suddenly created there, and will be simply classed as new species
Punk-eek is more a fabrication of media hoopla than a new concept, Dawkins and many others dismissed it as nothing new when it first came out.
Look, I obviously haven't made my point clear. I understand that evolution is dealing with events that happened a long time ago, and for which scant physical evidence now exists. I understand that because of these limitations, in most instances inference is the best scientists can hope for, and for that reason they must phrase their hypotheses in appropriatly careful language.
This is typical of all science. Nothing is taken as truth, empirical evidence is assumed to be due to reality, and all theories are tentative explanations of the evidence.
What I object to is the fact that many scientists are treating the difficulties incumbent in studying the deep past as a license to make any claim they like, and present it as "evidence".
For example, your authors use phrases like: "records suggest that...", and "is likely to be similar to..."
and yet you are perfectly comfortable in asserting:
Lactation demonstrates a new feature in members of the Cynodontia Clade that evolved through the adaptation of an existing feature to a new use.
Not a suggestion. Not a likelihood. A fact.
Fair enough: the evidence shows a clear point at which a new source of calcium was used, because there is an increase in the rate of growth of young organisms within the clade. The increased rate of growth is completely consistent with the rates of growth in mammals today, which is due to the calcium content of milk/s. It is also completely consistent with the rates of growth in marsupials and in monotremes, which is also due to the calcium content of milk/s. This consistency extends into the fossil record back to the time of Cynodontia, a fossil clade known to be a population that these lineages descended from due to the homologies in their fossil structures. In addition, the milk products in all three lineages contain homologous proteins, one in particular. Thus the evidence of increased growth in all three lineages is best explained by the emergence of lactation in general, and that one protein in particular, at one time - in Cynodontia.
It is a fact that Cynodontia exhibit this increased growth rate.
It is a fact that milk products in mammals, marsupials and monotremes share basic proteins that are homologous, one in particular.
If you disagree with this argument then you need to supply a different explanation for the facts.
I suggest you read the article again. The presence of the milk protein in all three daughter clades - eutheria (placental mammal), metatheria (marsupial mammals) and monotreme (egg laying mammals) - is indicative of common ancestry. Further development or loss of a feature after that ancestral point does not invalidate the ancestry, and marine mammals are a branch of placental mammals, well after the divide between eutheria, metatheria and monotreme .
What's to say Cynodonts weren't mammals? As far as I can tell from the research (correct me if I'm wrong) we can't even prove they laid eggs. They had a couple of extra bones in their jaw. Does that mean they weren't mammals? Are there rules a mammal has to abide by in order to be a mammal?
For example, can a mammal be egg-laying? Can a mammal be poisonous?
The Platypus is both.
If Cynodontia were mammals, all arguments about their evolution of lactation become moot.
They weren't mammals, they are ancestral to the eutheria clade, the metatheria clade, and the monotreme clade - they are older than the divisions between these later clades of animals, and this is marked by the jaw development that was completed in the mammaliforms. iirc. The platypus is a (venemous, male only) monotreme. All of these fossils also have the same developing jaw bone homologies which was completed before mammalia iirc, before becoming mammals per se and the division into the three clades. The platypus also has teeth during fetal development but loses them as they mature and their soft bill forms.
The development of the jaw\ear bone structure from a reptilian 3-bone jaw + 1 attached earbone, to a mammalian single bone jaw and detached 3-bone ear occurs during the evolution from therapsida to mammaliform, including several with two jaw joints, transitional between the two basic structures.
So the increased use of calcium likely occurred well before the division of the daughter clades, and their homologies in milk forms, jaw forms and other structures argue for common ancestry..
Enjoy.
Edited by RAZD, : corrections per bluejay (thanks)
False Logic again: the ear development is sequential
Hi Kaichos Man,
It is a common mistake that creationists make, to assume that several mutations must occur at once. Of course, it is part of creationist propaganda (falsehoods), rather than actual fact.
It's such an attractive idea, isn't it? You can just see the animation; the malleus and incus falling back, shrinking down as the dentary gets bigger and bigger, and then the two small bones eventually disappear into the ear, to play a brand new role there.
But if this actually happened, let's consider for a moment what is required in terms of known evolutionary mechanisms.
For each small, incremental step in this process:
1. At least three simultaneous mutations must occur, two to diminish the malleus and incus, one to enlarge the dentary.
2. The mutations must be perfectly complementary, i.e. the shrinkage of the malleus and incus must be perfectly offset by the growth of the dentary, otherwise a misshapen jaw will result- clearly a survival disadvantage.
3. A survival advantage must be conferred, significant enough to reach fixation.
Remember, these requirements are for each incremental step.
Curiously, what the fossil record actually shows is sequential development, so your basic assumption is false. First the dentiary bone extends into more of a jaw bone, then a second hinge forms before the mallues, stapes and incus move away to form an independent ear structure.
http://genesispanthesis.tripod.com/fossils/rept_mam.html
[quote]Fortunately, however, there are also a number of skeletal differences between reptiles and mammals. For one, reptiles have a mouth filled with several teeth which are more or less uniform in size and shape; they vary slightly in size, but they all have the same basic cone-shaped form. By contrast, mammals tend to have teeth which vary greatly in size and shape; everything from flat, multi-cusped molar teeth to the sharp cone-shaped canines. In reptiles, the lower jaw is comprised of several different bones, which hinge on the quadrate bone of the skull and the angular bone of the jaw. In mammals, however, the lower jaw is comprised of only one bone - the dentary, which hinges at the quadrate of the skull. In mammals, there are three bones in the middle ear, the malleus, incus and stapes (also known as the hammer, anvil and stirrup). In reptiles, there is only one bone - the stapes.
Colbert and Morales (1991, p. 127) describe the transitional nature of the tritylodonts in particular:
[indent]"In many respect[s], the tritylodont skull was very mammalian in its features. Certainly, because of the advanced nature of the zygomatic arches, the secondary palate and the specialized teeth, these animals had feeding habits that were close to those of some mammals . . . . Yet, in spite of these advances, the tritylodonts still retained the reptilian joint between the quadrate bone of the skull and the articular bone of the lower jaw. It is true that these bones were very much reduced, so that the squamosal bone of the skull and the dentary bone of the lower jaw (the two bones involved in the mammalian jaw articulation) were on the point of touching each other." [/indent]
Flank (1995) writes:
As Arthur N. Strahler puts it, "A transitional form must have had two joints in operation simultaneously (as in the modern rattlesnake), and this phase was followed by a fusion of the lower joint." (Strahler 1987, p. 414) ... Not only is this explanation not 'merely wishful conjecture', but it can be clearly seen in a remarkable series of fossils from the Triassic therapsids. The earliest therapsids show the typical reptilian type of jaw joint, with the articular bone in the jaw firmly attached to the quadrate bone in the skull. In later fossils from the same group, however, the quadrate-articular bones have become smaller, and the dentary and squamosal bones have become larger and moved closer together. This trend reaches its apex in a group of therapsids known as cynodonts, of which the genus Probainognathus is a representative. Probainognathus possessed characteristics of both reptile and mammal, and this transitional aspect was shown most clearly by the fact that it had TWO jaw joints--one reptilian, one mammalian."
"Probainognathus, a small cynodont reptile from the Triassic sediments of Argentina, shows characters in the skull and jaws far advanced toward the mammalian condition. Thus it had teeth differentiated into incisors, a canine and postcanines, a double occipital condyle and a well-developed secondary palate, all features typical of the mammals, but most significantly the articulation between the skull and the lower jaw was on the very threshhold between the reptilian and mammalian condition. The two bones forming the articulation between skull and mandible in the reptiles, the quadrate and articular respectively, were still present but were very small, and loosely joined to the bones that constituted the mammalian joint . . . Therefore in Probainognathus there was a double articulation between skull and jaw, and of particular interest, the quadrate bone, so small and so loosely joined to the squamosal, was intimately articulated with the stapes bone of the middle ear. It quite obviously was well on its way towards being the incus bone of the three-bone complex that characterizes the mammalian middle ear."
Next in the reptile-to-mammal transitional sequence are the cynodonts. Pictured here is Cynognathus, a classic example of the cynodont reptiles. Of course, when faced with a specimen such as this, one is forced to wonder if it can truly be called a "reptile". The skull appears basically mammalian, the hip structure seems basically mammalian as well, but with very distinct similarities to reptiles as well. Also notice that the grastral ribs and vertebrae seem to be forming a primitive breast-bone (sternum) - and strikingly resembles the gastral ribs/vertebrae of the earliest mammals from several orders. The gastral "floating" ribs have been reduced to almost nothing, and they are completely absent in mammals, yet very large in reptiles. This animal isn't quite a mammal, but it isn't quite a reptile either. This animal truly appears to be reptile and mammal. It is a perfectly intermediate form. [/quote]
Thus we see a sequence of changes as the jaw shifts from reptilian to mammalian, with the bones that form the mammal inner ear being freed up to specialize in hearing (rather than doing double duty in reptiles).
No multiple mutations needed, just a simple "step by step slowly he turns" process, typical of evolution in general, and the development of the mammalian ear in particular.
Remember, these requirements are for each incremental step. Anyone feel up to doing the maths? The probability would obviously run into the trillions-to-one against, but that shouldn't be a problem
As long as there were trillions of therapsids.
Who needs to do fictional maths when there is evidence that absolutely refutes the base assumption of multiple mutations? Not only is there a clear transition from one stage to the next, but there are a number of other discrete mammalian characteristics also showing development in stages.
An overbite or underbite, severe or not, is never going to be a survival advantage.
Okay, if you say so.
One can also compare the variation within a population to show that they could seesaw back and forth as one grew and then another shrank. These minor variations would be seen at the population\species level, while the overall trend is visible in the tree of descent.
We also have the evolution of the teeth going on at about the same time, so this may be what drives the change in the jaw bones - making room for the new kinds of teeth that are more fit for consumption.
Enjoy.
ps - could you (or a mod) reduce the picture sizes or stack them? I can't see the right side of the page.
moving on ... Foraminifera as a confirming example
Hi Kaichos Man,
You will know when I believe my argument has received a mortal blow (or been manoeuvred into apparent deadlock) because I'll probably stop talking about it and change the subject.
Thanks for admitting that you were wrong on the lactose and jaw evolution.
In the overall battle between Creationism and evolution, this could be termed retreating and attacking on another front.
In the overall battle between learning and denial, this would be true only if the "attacking on another front" does not consist of making the same uninformed arguments that have been refuted. Curiously, my experience is that this is the "declare victory and run away" defense of creationsts, similar to the Monty Python "run away run away" scene/s. The evidence on this thread thus far shows that your ability for "attacking on another front" is limited to repeating previous statements.
Agreed. But you seem to have left out the most important reason- that the majority of variation evident at the molecular area is in the functionally less important areas, namely junk DNA. One of Kimura's 5 principles is:
"(ii) Functionally less important molecules or parts of a molecule evolve (in terms of mutant substitutions) faster than more important ones."
Kimura's take on the macroevolutionary process is illuminating:
quote:(i) A population is liberated from the preexisting selective constraint. (ii) There is a sudden increase or boom of neutral variations under relaxed selection. In this stage, gene duplication in addition to point mutation must play a very important role in producing genetic variations. Needless to say, their fate is largely determined by random drift. (iii) The latent selection potential of some of the neutral mutants is realized. In other words, some of the accumulated neutral mutants (at the phenotypic level) turn out to be useful in a new environment, which the species then exploits. (iv) Intergroup competition and individual selection lead to extensive adaptive evolution, creating a radically different taxonomic group adapted to a newly opened ecological niche.
(normal quote formatting added)
Now let's look at an example of that kind of situation in the fossil record and see what it shows:
quote:Some scientists have theorized, but never been able to demonstrate, that in the absence of competition, an explosion of life takes place. The evolution of new species is greatly accelerated, and a profusion of body shapes and sizes bursts across the horizon, filling up vacant spaces like weeds overtaking a pristine lawn. An array of new forms fan out into these limited niches, where crowding soon forces most of the new forms to spin out into oblivion, as sparks from a flame. ... As revealed by the ancient record left by the foram family, the story of recovery after extinction is every bit as busy and colorful as some scientists have long suspected.
"What we've found suggests that the rate of speciation increases dramatically in a biological vacuum," Parker said. "After the Cretaceous extinction, the few surviving foram species began rapidly propagating into new species, and for the first time we're able to see just how this happens, and how fast."
As foram survivors rush to occupy their new habitats, they seem to start experimenting will all sorts of body shapes, trying to find something stable, something that will work, Arnold said. Once a population in a given habitat develops a shape or other characteristic that stands up to the environment, suddenly the organisms begin to coalesce around what becomes a standardized form, the signature of a new species.
As the available niches begin to fill up with these new creatures, the speciation rate begins to slow down, and pressure from competition between species appears to bear down in earnest. The extinction rate then rises accordingly.
This scenario, Arnold says, suggests that the speciation process is sensitive to how fully packed the biosphere is with other species, not the number of individuals. Ecologists, in referring to a given environment's ability to sustain life as its carrying capacity, generally mean the natural limit, in sheer numbers, of individual organisms that any environment can support, as opposed to the number of different kinds of organisms.
"This is an intriguing concept -- a species carrying capacity, so to speak," Arnold says. "This implies that the speciation process is sensitive to how many species are already out there."
In other words, exactly what Kimura suggested is recorded in detail in this fossil record, a fossil record that is nearly complete:
quote:Drs. Tony Arnold (Ph.D., Harvard) and Bill Parker (Ph.D., Chicago) are the developers of what reportedly is the largest, most complete set of data ever compiled on the evolutionary history of an organism. The two scientists have painstakingly pieced together a virtually unbroken fossil record that shows in stunning detail how a single-celled marine organism has evolved during the past 66 million years. Apparently, it's the only fossil record known to science that has no obvious gaps -- no "missing links."
"It's all here -- a complete record," says Arnold. "There are other good examples, but this is by far the best. We're seeing the whole picture of how this organism has changed throughout most of its existence on Earth."
It's interesting that Kimura sees natural selection as an essentially conservative force, from which "liberation" is required before evolution is possible (step i). This is relevant to the parallel discussion on stasis.
Which is, of course, your opinion about how Kimura sees natural selection and not fact based on statements from Kimura. Once again we see that your opinion is not a good predictor of reality.
Biologists talk about levels of selection pressure. This pressure always exists, but it varies from high to low, depending on the complete ecology. When selection pressure is high, the organisms are constrained by that pressure from passing on any extraneous features, but when selection pressure is low, the organisms are less constrained by the need for survival and reproduction, and thus are able to engage in some extraneous features.
The difference between this and what you said, is that evolution under high selective pressure can be actively changing a population rather than conserving it.
And then he answers it:
quote:It is generally believed that, in contrast to the neutralist view of molecular evolution, evolutionary changes at the phenotypic level are almost exclusively adaptive and caused by Darwinian positive selection. However, I think that even at the phenotypic level, there must be many changes that are so nearly neutral that random drift plays a significant role"
Emphasis added. Carefully worded, but I think we can all (if you'll excuse the terrible pun) catch his drift.
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The amazing thing is that you think this is surprising or revolutionary. Selection that does not involve death or incapacity of the individual due to genetic misinformation occurs at the level of the individual, and this selection is based on the phenotype. The genotype has had it's say, now it is the job of the individual at the phenotype level to survive and reproduce, or all the selection at the genetic level is for naught.
Now the question is whether every trait expressed in the phenotype leads to selection. When you see patterns of coloration that are virtually ignored and that play no effect on survival or sexual selection, then it should be fairly obvious that traits too can be neutral (or nearly neutral) to selective pressure.
ie - evolution with natural selection adapts species to changes in habitats, while evolution with genetic drift provides variations within populations that over time can change a population into a different species.
An example of this is provided by the fossil record of Pelycodus:
The numbers down the left hand side indicate the depth (in feet) at which each group of fossils was found. As is usual in geology, the diagram gives the data for the deepest (oldest) fossils at the bottom, and the upper (youngest) fossils at the top. The diagram covers about five million years.
The numbers across the bottom are a measure of body size. Each horizontal line shows the range of sizes that were found at that depth. The dark part of each line shows the average value, and the standard deviation around the average.
The dashed lines show the overall trend. The species at the bottom is Pelycodus ralstoni, but at the top we find two species, Notharctus nunienus and Notharctus venticolus. The two species later became even more distinct, and the descendants of nunienus are now labeled as genus Smilodectes instead of genus Notharctus.
As you look from bottom to top, you will see that each group has some overlap with what came before. There are no major breaks or sudden jumps. And the form of the creatures was changing steadily.
Here you see a gradual increase in size in the population resulting in several species classifications as they move the population out of the range of the previous population. If natural selection were "conservative" as you claim, then this lineage should be vertical from P. ralstoni to N. nunienus, so you get a double whammy here: genetic drift accumulating into gradual increase in size, and lack of "conservation" by natural selection.
Natural selection would not constrain this evolution as long as each population was able to survive and mate at each level of the progression.
quote:The second is the "conservative nature" of the changesi.e., functionally less important molecules, or portions of molecules, evolve faster than more important ones
Which does not make it a conservative force to maintain the population in stasis as you claimed. You have mixed two meanings of conservative, the fallacy of equivocation. You still have changes.
I notice you did not respond to the rest of my post, so you must agree with that yes?
Message 167 You will know when I believe my argument has received a mortal blow (or been manoeuvred into apparent deadlock) because I'll probably stop talking about it and change the subject. In the overall battle between Creationism and evolution, this could be termed retreating and attacking on another front.
So anytime you fail to answer we can take this as your accepting that your argument has "received a mortal blow (or been manoeuvred into apparent deadlock)" ... where the "deadlock" is that you cannot figure a way to reply that isn't already answered.
Re: moving on ... Foraminifera as a confirming example
Hi Kaichose Man,
I have changed my position on mammalian jaw evolution, as a result of my own research into hox genes Dlx5&6. You can claim some credit for forcing me to undertake this research.
Thanks, but I am more interested in your learning things than in taking credits.
As for lactation, that remains one of the worst examples of an evolutionary "just so" story I've ever come across.
Again, this is just your opinion, and nothing you have said has come close to challenging the explanation provided that covers the facts.
It's not good science, RAZD.
Not all science is top shelf stuff, it just needs to explain the evidence, as this does. No paradigms are shifted by this knowledge, and the conclusion is not even much of a surprise, given what we know about mammal evolution and the common ancestry of the three clades of mammals.
Kimura wrote:"What I want to emphasize is that relaxation of natural selection is the prerequisite for new evolutionary progress'. -ergo- If natural selection is not relaxed, evolution will not progress.
First off, your logic is false because evolution proceeds regardless of natural selection. You have equivocated "new evolutionary progress" with ALL evolutionary progress.
Secondarily, "new" evolutionary trends would proceed when new opportunities open up that did not exist before, either by discovery of a new ecology or by extinction of organisms around a species making more opportunities available in the current ecology.
Thirdly, natural selection is not constant, it is in flux as a response to climate change, season change, change in the balance between predator and prey, etc etc etc.
Fourth and finally, the appeal to authority is a logical fallacy. Kimura is an authority on molecular biology, but he is also a person with opinions. The evidence speaks louder that Kimura's words and way louder than your half-informed attempts to wield them into an argument to falsify evolution.
The facts show evolution occurs. The facts show that hereditary traits change in populations from generation to generation, as a result of added variation provided by mutations, the spread of neutral traits by drift, and the selection of traits that benefit individual survival and breeding, changing the frequency of hereditary traits in descendant populations.
The facts show that evolution adds information to the population genome of evolving species. The facts show that traits exist in new populations that did not exist in ancestral populations.
-ergo- Stasis.
Another invalid conclusion based on poor logic and an uninformed opinion.
Yes, the fact that the Lucy fossil is only ~40% complete means that several parts need to be added to flesh out the full skeleton. When the parts of Lucy are mirrored (bilateral symmetry) this increases to ~60%.
However this is not "adding traits" to the fossil, so you are equivocating on the meaning of adding if that is your intent. Such poor logic is rather humorous (a) as an attempt at an intelligent response, and (b) because once again, the rest of the picture is fairly complete when we add in the bits and pieces from other known fossils of the same species.
quote:Australopithecus afarensis is an extinct hominid which lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A. afarensis was ancestral to both the genus Australopithecus and the genus Homo, which includes the modern human species, Homo sapiens. The most famous fossil is the partial skeleton known as Lucy.[1][2]
Cast of the remains of "Lucy"
Compared to the modern and extinct great apes, A. afarensis has reduced canines and molars, although they are still relatively larger than in modern humans. A. afarensis also has a relatively small brain size (~380-430cm) and a prognathic (i.e. projecting anteriorly) face.
The image of a bipedal hominin with a small brain and primitive face was quite a revelation to the paleoanthropological world at the time. This was due to the earlier belief that an increase in brain size was the first major hominin adaptive shift. Before the discoveries of A. afarensis in the 1970s, it was widely thought that an increase in brain size preceded the shift to bipedal locomotion.
However, there are also a number of traits in the A. afarensis skeleton which strongly reflect bipedalism. In overall anatomy, the pelvis is far more human-like than ape-like. The iliac blades are short and wide, the sacrum is wide and positioned directly behind the hip joint, and there is clear evidence of a strong attachment for the knee extensors. While the pelvis is not wholly human-like (being markedly wide with flared with laterally orientated iliac blades), these features point to a structure that can be considered radically remodeled to accommodate a significant degree of bipedalism in the animals' locomotor repertoire. Importantly, the femur also angles in toward the knee from the hip. This trait would have allowed the foot to have fallen closer to the midline of the body, and is a strong indication of habitual bipedal locomotion. Along with humans, present day orangutans and spider monkeys possess this same feature. The feet also feature adducted big toes, making it difficult if not impossible to grasp branches with the hindlimbs. The loss of a grasping hindlimb also increases the risk of an infant being dropped or falling, as primates typically hold onto their mothers while the mother goes about her daily business. Without the second set of grasping limbs, the infant cannot maintain as strong a grip, and likely had to be held with help from the mother. The problem of holding the infant would be multiplied if the mother also had to climb trees. The ankle joint of A. afarensis is also markedly human-like.
quote:The Woranso-Mille site is located in the Central Afar region, about 325 miles northeast of the capital Addis Ababa and 25 miles east of a small town called Mille. The multidisciplinary and multinational team focuses primarily on finding early human fossil remains dating back millions of years. The team has thus far collected more than 40 fossil specimens of early humans, including one partial skeleton and 1,900 fossil specimens of other animals representing more than 30 species useful in reconstructing the ancient environment in which our early ancestors lived.
The fossils collected at Woranso-Mille have been dated to between 3.5 and 3.8 million years ago. Little is known about early human fossils from this time period, sandwiched between two early species of human ancestors known as Australopithecus afarensis (the species of Lucy) and Australopithecus anamensis. New discoveries within this timeframe are critical to understanding both the relationship between these two species and the larger story of human origins. All of the collected fossil specimens from the Woranso-Mille study area are currently being curated for analysis and subsequent publication.
quote:Inhabiting eastern Africa between four and three million years ago, Australopithecus afarensis was a long-lived species that may have given rise to the several lineages of early human that appeared in both eastern and southern Africa between two and three million years ago. For its antiquity, A. afarensis is one of the better known species of early human, with specimens collected from over 300 individuals. It is a species that exhibits many cranial features which are reminiscent of our ape ancestry, such as a forward protruding (prognathic) face, a "U-shaped" palate (with the cheek teeth parallel in rows to each other similar to an ape) and not the parabolic shape of a modern human, and a small neurocranium (brain case) that averages only 430cc in size (not significantly larger than a modern chimpanzee).
The specimens recovered have given representative examples of almost all of the bones of the A. afarensis skeleton. From this, it is clear that there are many significant difference between A. afarensis and its ape predecessors, one of which is crucial to later human evolution, bipedality.
Putting these many parts all together and mirroring ones missing from one side we obtain this composite Australopithecus afarensis
Notice how few places are not taken by brown (indicates Lucy fossil bones) and white (from other fossils and mirrored parts), and that this shows how complete our knowledge of the composite skeleton is. This then becomes the frame on which a 3-D Full size fleshed out reconstruction is made, using known sinew, muscle and skin patterns, and this is compared to how people walk and how this skeleton matches the evidence of footprints left in stone:
quote:Computer simulations using dynamic modelling of the skeleton's inertial properties and kinematics have indicated that A. afarensis was able to walk in the same way modern humans walk, with a normal erect gait or with bent hips and knees, but could not walk in the same way as chimpanzees. The upright gait would have been much more efficient than the bent knee and hip walking, which would have taken twice as much energy.[5][6] It appears probable that A. afarensis was quite an efficient bipedal walker over short distances, and the spacing of the footprints at Laetoli indicates that they were walking at 1.0 m/s or above, which matches human small-town walking speeds.[7]
A reconstruction of a female Australopithecus afarensis
Note that this museum display puts the reconstruction with the Laetoli footprints, more fossil evidence of bipedal walking:
Species: Australopithecus afarensis Age: 3.6 million years Date of Discovery: 1974-1975 Location: Laetoli, Tanzania Discovered by: Mary Leakey
The gait and length of stride match the fossil reconstruction, the footprint pattern matches the foot bones of A. afarensis.
Evidence does not lie. Multiple bits of evidence makes mistaken interpretations less and less likely. You are the one who is kidding yourself if you think this reconstruction is a gross misrepresentation of reality, when the validity is demonstrated by many multiple and overlapping fossils from many individuals that have already been uncovered. More evidence will only serve to "flesh-out" the skeleton further.
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