lucaspa

Good for you! Fortunately, you've got a good Sticky thread in this forum on the evolution of humans. My contribution is the last post listing some of the transitional individuals connecting species to species in our ancestry.

Before I start, remember I have been saying that creationism is a falsified theory. It is wrong. Mokele: "We're flat-out stating that there is no evidence that supports creationism. None, Nada, zip. None has even been presented. If you want to challenge this, show evidence. " This is where Mokele was not reading my posts. Looking into history, evidence supporting creationism can be found in papers in the period 1700 -1831. Not only that, but Gentry published a couple of papers in Science with evidence that supported a young earth: Gentry, R., 1968, Fossil alpha-recoil analysis of certain variant radioactive halos, Science, 160:1228-1230. Gentry, R., 1970, Giant radioactive halos: indicators of unknown radioactivity?, Science, 169:670-673. Gentry, R., 1974, Radiohalos in a radiochronological and cosmological perspective, Science, 184:62-66. Gentry, R. and others, 1976, Radiohalos in coalified wood: new evidence relating to the time of uranium introduction and coalification, Science, 194:315-318. So, even in recent history, Mokele's claim "there is no evidence that supports creationism. None, Nada, zip. None has even been presented." is false. What we are into now is an argument whether that evidence is valid. Of course, Mokele didn't put that qualifier into his claim. So now anyone using the "there is no evidence" argument against a creationist is bogged down in an endless no-win argument about whether Gentry's evidence is valid or not. Looking back in history, in the 1820s, Buckland and Sedgwick both published studies ascribing surface morrains in Europe to a world-wide flood. In 1695 John Woodward listed the fossil record and sedimentary rock as showing that a world-wide flood had dissolved or eroded the particulate matter of the earth's surface and then redeposited them in general order of specific gravity. (Arbuthnot and Bellers falsified this one 10 to 20 years later.) Silliman in 1823 and Hitcock in 1837 in America noted that surficial deposists were consistent with a world-wide flood. (they were also consistent with glaciation, which became dominant after the Flood was falsified.) Prestwich in 1795 listed several bone-filled fissures and caves and rubble drift deposits on top of raised beaches in southern England and the wester Med as evidence of a post-glacial inundation followed by a rapid elevation. (The features Prestwich listed were later accounted for as periglacial phenomenon.) You can find a more detailed list of all this in the books Genesis and Geology by Charles Gillespie and The Biblical Flood: A Case History of the Church's Response to Extrabiblical Evidence by Davis A. Young. Both are professional geologists. The work of Blythe supported creationism, since he saw selection keeping species constant. Richard Owen, a contemporary of Darwin, wrote papers supporting creationism. Even Lyell supported creationism as applied to species in his Principles of Geology: "Each species 'was endowed at the time of its creation, with the attributes of organization by which it is now distinguished." Only limited variations within a type have ever occurred. Each species, itself immutable, probably takes its origin frmo a single pair, such pairs having "been created in succession at such times and in such places as to enable them to multiply and endure for an appointed period, and occupy an appointed place on the globe." CC Gillespie, Genesis and Geology 130-131. Now, read closely, what matters is the evidence AGAINST a theory. Taken in isolation, the fossils at Dinosaur National Monument are "evidence for" creationism. Why? Because you have animals jumbled together by a flood -- and you could say that this flood was the Flood. if you look only at those fossils in that location and ignore all other data. So, why don't we consider all this "evidence for" creationism today. Because creationism has been falsfied. That is, data has been found that could not possibly be there IF creationism were true! True statements cannot have false consequences and creationism has false consequences. Therefore it can't be true. Not only does the evidence "for" creationism still exist, but the evidence falsifying creationism still exists! Back to Popper and "evidence for" "1. It is easy to obtain confirmations, or verifications, for nearly every theory -- if we look for confirmations. 2. Confirmations should count only if they are the result of risky predictions. 3. Every 'good' scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is. 4. Every genuine test of a theory is an attempt to falsify it, or to refute it. 5. Confirming evidence should not count *except when it is the result of a genuine test of the theory:* and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. "

You're welcome. LOL! you are going from biology you got in Middle School? Just how detailed do you think that could have been? OK, if biology is tedious and you haven't even looked at it since a Middle School class 5 years ago (you didn't take high school biology?), then let me suggest that you lurk and, if not lurking, ask questions? It's OK that you "can't be bothered with biology", we all have different interests. But that attitude severely limits the contribution you can make to a discussion involving biology. Your data was superficial at best, is now half-forgotten, and you aren't seeking more education in the subject.

I would question this. I would need to see some quantitative data on female pelvic girdles. The human population is so large and 200 years so short (10 generations) that I doubt there has been an overall shift in pelvic girdles. Yes, there is sexual selection, no doubt about it. And I would even say that recently men in the West are choosing as you describe. What I question is whether that selection has been strong enough and long enough to shift the mean in female pelvic girdles. Also, the ideal you are describing is in Western civilization. That's a growing segment of the human population, but hardly all humans! It is true that medical/surgical intervention is becoming more frequent, but that has nothing to do with narrower pelvi. Instead, there is a huge number of factors that are coming into play in the West for that: 1. Reimbursement (a surgical procedure can be billed at a much higher rate than natural childbirth) 2. Avoiding malpractice suits (the baby is less likely to have problems with C-section) 3. Convenience for the obstetrician (no waiting for hours while the woman does labor and missing his tee time) 4. The instant gratification and avoidance of pain in modern culture: women sometimes demand C-section so they don't have to go thru labor and can schedule when to have the birth 5. The idea that even one death in childbirth is too many. Therefore we aren't allowing evolution, and natural selection, to take their course.

We can "discard" a theory without it having formal acceptance in a society. "Discard" is simply the consensus that the theory is wrong. Can you please explain what you mean by "It certainly offers considerably more meat than the discredited savannah theory"? It appears that we are not dealing with a dichotomy -- aquatic or savannah. http://en.wikipedia.org/wiki/Savanna_Theory There are other theories out there, such as "mosaic" and a new "littoral" theory on where humans have lived. Also, if the aquatic ape theory is "beginning to garner some support", can you be more specific? Where? What papers have recently been published on it? I find a 1997 paper below, and nothing more recent in PubMed: Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis.Langdon JH. Department of Biology, University of Indianapolis, Indiana 46227, USA. "Conventionally, anthropologists have sought to explain a multitude of unique features of modern humans as the outcome of a single adaptive breakthrough. These "umbrella hypotheses" are aesthetically appealing because they appear to be parsimonious. As internally consistent hypotheses about the past, they are very difficult to prove incorrect in an absolute sense. Anthropology has often rejected them by consensus without developing explicit reasons. This essay explores one example of these models, the Aquatic Ape Hypothesis, the proponents of which continue to argue that they have not received a fair hearing among anthropologists. The hypothesis is troubled by inconsistencies and has not been reconciled with the fossil record. More importantly, its claim to parsimony is false. The numerous "explanations" for individual anatomical traits that it generates constitute premises that are not better founded than competing terrestrial "explanations". The unifying theme of aquatic adaptation is considerably less parsimonious than the assumption that our lineage has always been terrestrial. Finally, the mosaic pattern of hominid evolution demonstrated by the fossil record will not support this or any single cause theory. Most of these criticisms have been previously voiced in one form or another, yet umbrella hypotheses ranging from mainstream science to the paranormal maintain their popularity among students, general audiences, and scholars in neighboring disciplines. One reason for this is that simple answers, however wrong, are easier to communicate and are more readily accepted than the more sound but more complex solutions. Evolutionary science must wrestle with this problem both in its own community and in the education of the public."

Actually, polypeptides ARE proteins. Different name, same thing. And the experiment is just one way to get amino acids to string together to make proteins. It happens at hydrothermal vents. It can also happen in a tidal pool as it evaporates under the sun. Rohlfing, DL. Thermal polyamino acids: synthesis at less than 100°C. Science 193: 68-70, 1976. Syren RM, Sanjur A, Fox SW Proteinoid microspheres more stable in hot than in cold water. Biosystems 1985;17(4):275-80 (protocells at hydrothermal vents) Yanagawa, H. and K. Kobayashi. 1992. An experimental approach to chemical evolution in submarine hydrothermal. systems. Origins of Life and Evolution of the Biosphere 22: 147-159. Marshall, W. H. 1994. Hydrothermal synthesis of amino acids. Goechimica et Cosmochimica Acta 58: 2099-2106. McAlhaney WW, Rohlfing DL. Formation of proteinoid microspheres under simulated prebiotic atmospheres and individual gases. Biosystems 1976 Jul;8(2):45-50 Fouche-CE Jr; Rohlfing-DL Thermal polymerization of amino acids under various atmospheres or at low pressures. Biosystems. 1976 Jul; 8(2): 57-65 SW Fox, Thermal polymerization of amino-acids and production of formed microparticles on lava. Nature, 201: 336-337, Jan. 25, 1964. Hennon, G, Plaquet, R, Biserte, G. The synthesis of amino acid polymers by thermal condensation at 105° without a catalyst. Biochimie 57: 1395-1396, 1975. Heinz, B, Reid, W. The formation of chromophores through amino acid thermolysis and their possible role as prebiotic photoreceptors. BioSystems 14: 33-40, 1981. But it doesn't matter. The experiment has been repeated with several types of non-reducing atmosphere and the results are essentially the same: 1. Kawamoto K, Akaboshi H. Study on the chemical evolution of low molecular weight compounds in a highly oxidized atmosphere using electical discharges.**Origins of Life and Evolution of the*Biosphere 12: 133-141, 1982.

We were discussing the relationship of creationism to science. And yes, I'm talking about science and I haven't posted any "creationist crap". Mokele, you should know that from my other posts. After all, we are discussing mechanisms of evolution in another thread -- specifically genetic drift. Nowhere in my posts do you see any rejection of evolution, do you? Also remember I'm making a much stronger statement than you about creationism. I'm saying creationism is a falsified theory. That is, it is WRONG. You are merely saying creationism is not science. That says nothing about its truth value. So, we are talking science and the philosophy of science. Using ad hominem arguments and closing the thread isn't going to make the data go away. Mokele: "Creationism may have been a theory, but it was never scientific one, since it cannot be tested (since God is *defined* as unknowable) and cannot be falsified (since there's always the 'God of the gaps'). It fails to fulfill these, it's not science, end of story." Notice the source here, Mokele. Kitcher is a philosopher of science and an evolutionist. ""There is another way to be a Creationist. One might offer Creationism as a scientific theory: Life did not evolve over millions of years; rather all forms were created at one time by a particular Creator. Although pure versions of Creationism were no longer in vogue among scientists by the end of the eighteenth century, they had flourished earlier (in the writings of Thomas Bumet, William Whiston, and others). Moreover, variants of Creationism were supported by a number of eminent nineteenth-century scientists-William Buckland, Adam Sedgwick, and Louis Agassiz, for example. These Creationists trusted that their theories would accord with the Bible, interpreted in what they saw as a correct way. However, that fact does not affect the scientific status of those theories. Even postulating an unobserved Creator need be no more unscientific than postulating unobservable particles. What matters is the character of the proposals and the ways in which they are articulated and defended. The great scientific Creationists of the eighteenth and nineteenth centuries offered problem-solving strategies for many of the questions addressed by evolutionary theory. They struggled hard to explain the observed distribution of fossils. Sedgwick, Buckland, and others practiced genuine science. They stuck their necks out and volunteered information about the catastrophes that they invoked to explain biological and geological findings. Because their theories offered definite proposals, those theories were refutable. Indeed, the theories actually achieved refutation. In 1831, in his presidential address to the Geological Society, Adam Sedgwick publicly announced that his own variant of Creationism had been refuted: Having, been myself a believer, and, to the best of my power, a propagator of what I now regard as a philosophic heresy ... I think it right, as one of my last acts before I quit this Chair, thus publicly to read my recantation. We ought, indeed, to have paused before we first adopted the diluvian theory, and referred all our old superficial gravel to the action of the Mosaic Flood. For of man, and the works of his hands, we have not yet found a single trace among the remnants of a former world entombed in these ancient deposits. In classing together distant unknown formations under one name; in simultaneous origin, and in determining their date, not by the organic remains we have discovered, but by those we expected, hypothetically hereafter to discover, in them; we have given one more example of the passion with which the mind fastens upon general conclusions, and of the readiness with which it leaves the consideration of unconnected truths. (Sedgwick, 1831, 313-314; all but the last sentence quoted in Gillispie 1951, 142-143)" Philip Kitcher, Abusing Science: The Case Against Creationism pp125-126 Did you see that, Mokele? Creationism was falsified. It's not "unfalsifiable". Instead, creationism is both falsifiable and falsified. Mokele: "We all know perfectly well what "creationism" means, thanks the the actions of religious zealots in the US." But "creation" and "creationism" are not the same thing. Creation is a theological statement: God created. Creationism is a specific method that God used to create. Theistic evolutionists (such as Charles Darwin, Kenneth Miller, Francisco Ayala, and myself) all believe in creation. We all, however, reject creationism. Lucaspa: "There is evidence for ANY and EVERY scientific theory, if that is what you are looking for." This comes from Karl Popper and the Duhem-Quine Thesis. "1. It is easy to obtain confirmations, or verifications, for nearly every theory -- if we look for confirmations." Karl Popper, Conjectures and Refutations, 1963 p 38. The Duhem-Quine Thesis states that, for any limited amount of data, there are an infinite number of theories to explain it. The corollary for that is, of course, that for any theory there is going to be a limited amount of data that supports it. The examples you gave was simply data that hadn't been found YET. (of course, since Godzilla is an admitted fictional character, it can't be a scientific theory) Mokele: "Philosophy is a waste of time. We outgrew it the moment it gave birth to the scientific method." Mill was stating philosophy ABOUT the scientific method! How do we evaluate theories in order to separate the correct ones from the incorrect ones? That's the problem of the scientific method Mill and others have grappled with. It's called the philosophy of science. Call it "how and why we do science the way we do science". Popper gave another way of evaluating theories: show them to be false. Mokele: "Wrong. A theory without evidence for it is worthless." Most theories start out without evidence. Most get falsified, of course. But some end up earning the scientists who first proposed them Nobel Prizes: "Volume 13, #22 The Scientist November 8, 1999 http://www.the-scientist.com/yr1999/nov/halim1_p1_991108.html Nobel Laureate Ready To Head Back to Lab Author: Nadia S. Halim Date: November 8, 1999 Courtesy of Rockefeller University Nobel laureate Günter Blobel -------------------------------------------------------------------------------- When Günter Blobel and David Sabatini first proposed the signal hypothesis in 1971, the whole thing was simply ignored. There was not a shred of evidence to support it. " The theory was not worthless after all, was it? Another example is tachyons: "1. Tachyons: can we rule them out. The special theory of relativity has been tested to unprecedented accuracy, and appears unassailable. Yet tachyons are a problem. Though they are allowed by the theory, they bring with them all sorts of unpalatable properties. Physicists would like to rule them out once and for all, but lack a convincing nonexistence proof. Until they construct one, we cannot be sure that a tachyon won't suddenly be discovered." Paul Davies, About Time, 1994. There is no evidence for tachyons. Does that make Special Relativity worthless? The point here, Mokele, is that saying "there is no evidence for creationism" is a worthless argument for evolution! This doesn't make creationism correct. Creationism is still wrong even if you use a mistaken argument against it. What saying "there is no evidence for creationism" does is show 1) an ignorance of the history of creationism and how it was falsified. 2) an ignorance of how science is done. 3) ignores the most effective arguments you have against creationism: data that shows creationism can't possibly be correct. Read this and think about it carefully, please: " Creationists make assertions about the world. Once made, those assertions take on a life of their own. Because they do, we can assess the merits or demerits of creationist theory without having to speculate about the unsavoriness of the mental habits of creationists. What we do, of course, is to examine the empirical evidence relevant to the creationist claims about earth history. If those claims are discredited by the available evidence (and by "discredited" I mean impugned by the use of rules of reasoning which legal and philosophical experts on the nature of evidence have articulated), then Creationism can safely be put on the scrap heap of unjustified theories. But, intone Ruse and Overton, what if the creationists still do not change their minds, even when presented with what most people regard as thoroughly compelling refutations of their theories? Well, that tells us something interesting about the psychology of creationists, but it has no bearing whatever on an assessment of their doctrines. After all, when confronted by comparable problems in other walks of life, we proceed exactly as I am proposing, that is, by distinguishing beliefs from believers. When, for instance, several experi-ments turn out contrary to the predictions of a certain theory, we do not care whether the scientist who invented the theory is prepared to change his mind. WA do not say that his theory cannot be tested, simply because he refuses to accept the results of the test. Similarly, ajury may reach the conclusion, in light of the appropriate rules of evidence, that a defendant who pleaded innocent is, in fact, guilty. Do we say that the defendant's assertion "I am innocent" can be tested only if the defendant himself is prepared to admit his guilt when finally confronted with the coup de grace? In just the same way, the soundness of creation-science can and must be separated from all questions about the dogmatism of creationists. Once we make that rudimentary separation, we discover both (a) that creation-science is testable and falsifiable, and (b) that creation-science has been tested and falsified-insofar as any theory can be said to be falsified. But, as I pointed out in the earlier essay, that damning indictment cannot be drawn so long as we confuse Creationism and creationists to such an extent that we take the creationists' mental intransigence to entail the immunity of creationist theory from empirical confrontation." Larry Laudan, "More on Creationism", Chapter 24 in But Is It Science? Edited by M Ruse pp 363-366

lucaspa: "If I remember correctly (and let me check this tonight), the number of generations required for fixation by genetic drift is 2^N/2." OK, I checked and my memory was faulty in regard to the equation. The number of generations required for fixation purely by genetic drift is 4N. N is the effective size of the population -- it is the number of individuals participating in breeding. So, back to "a few thousand" large carnivores. Let's do the minimum of 3,000. That's still 12,000 generations (a lot less than I originally calculated) for fixation by genetic drift alone. However, we have to take the number of years between an individual is born and when it can sire an offspring. For humans generation time is about 20 years. That would be 240,000 years for fixation by genetic drift. Since H. sapiens as a species is, at most, 200,000 years old, that is longer than the lifespan of our species. Lions, cheetahs, tigers, etc. have shorter generation times. For instance, lions reach sexual maturity in about 3 years. So fixation by genetic drift could occur in that species in 36,000 years if the population were 3,000. And yes, to answer questions I'm sure will be asked, if the species is split into demes with smaller N, then genetic drift can take place within the demes within a reasonable period of time.

You are confusing natural selection and evolution. Evolution is, briefly, "descent with modification". Natural selection is a major part of the "modification". Does that help your confusion? We are born with our alleles and our genome does not change during our lifetime. Now, in a population of individuals, each individual varies. So if you plot some character on the x-axis vs the number of individuals who have that character on the y-axis, you get a bell-shaped curve. Let's try just fur length in deer. Say you have the top of the curve (mean) at 1.0 cm and the standard deviation of the curve is 0.25. This means that 2/3 of all the individuals in the population will have fur length between 0.75 and 1.25 cm. 95% of the individuals will have fur length between 0.5 and 1.5 cm. But the fur length of each individual is set by the alleles. Now suppose you have a climate growing colder and, over the next ten years, you have average colder winters that result in all deer below 0.75 cm fur length dying of cold. Now you've shifted the bell shaped curve to the right. The average fur length for the population is now 1.2 cm. In addition, some deer are born with fur length longer than 1.5 cm. These deer do even better over the next 100 years. So they leave even more offsprings and that shifts the curve even more to the right. Coming back 110 years later, you have a population where the average fur length is now 1.75 cm and the standard deviation is still 0.25. So 95% of the deer have fur length between 1.25 cm and 2.25 cm. The population is different from the original First, we don't have to be arbitrary and invent "fitness bonus". Fitness is the ratio of the progeny actually produced to the progeny expected from Mendelian inheritance. You can see that it is going to be a fraction. From that you get a selection coefficient s = 1 - fitness. So s is between -1 and 1 and 0 = neutral. A page you want is http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/Hardy_Weinberg.html You are now talking about polygenic traits. The fallacy you are working under is that relative fitness of alleles is additive when you do a polygenic trait. But remember, it is the trait being selected. So the trait has a selection coefficient. Or even the set of alleles has a fitness coefficient. So the ration doesn't decrease the way you say. In a polygenic trait if a1bcde has s = 0.2 then a1 has s = 0.2. The selection coefficient isn't "diluted" like you are doing. Now that makes your problem go away, doesn't it? It doesn't. Instead, what you do is add more terms to the equation, but the power remains the same. No, because the term "fixation" refers to a specific allele, not a relative term. So we speak of fixation of a1. If a1 is lost, that doesn't say anything about a2, a3, etc. Also, if you use the plural "alleles", you don't have fixation of any of them. Because fixation is when ONE allele only is present in the population. There is no "above/below base chance level" in genetic drift. In genetic drift, the allele frequency changes by pure chance. If you start out with 2 alleles at a locus, by pure chance one allele will be fixed and the other eliminated -- eventually. Of course, if the population is "large", that "eventually" is so slow that the gene frequency of a1 and a2 doesn't change from generation to generation. However, if the population is very small (<50 breeding pairs), then losing just one individual can skew the process. Let's take simple examples. We have 10,000 individuals (5,000 breeding pairs) and the frequency of both a1 and a2 is 0.5 (5,000 individuals each of a1 and a2). So in the next generation one of the a1 dies accidentally so we have 4,999 of a1 and 5,000 of a2. The frequency of a1 is now 4999/9999 = 0.5 BUY, we have 10 breeding pairs (20 individuals) with 10 of a1 and 10 of a2. One of the a1 dies in the next generation. Now we have 9 a1 out of population of 19 = 0.474. The frequency has shifted quite a bit by chance. So the chance that one or the other allele will be fixed by chance alone increases if the population decreases. Extinction lowers a population to a very few individuals right before the end, doesn't it? Founder events are defined as involving 2-10 individuals. No, two alleles with equal fitness will reach equilibrium at 0.5 in a large population. In a small population, they will be subject to genetic drift like any other allele. Genetic drift is independent of fitness.

So you meant DNA, not "polymer"? Now, what did you mean by "express overtime in the population"? You do know there are lots of polymers, don't you? Protein is a polymer of amino acids. To start with the question at the end: No, working with populations is not staying at "arms distance" since it is the characteristics of the population that changes in evolution. Yes, populations are made up of individuals, but individuals stay the same through their lifetimes. Individuals are born with their genome, and that genome doesn't change during the lifetime of the individual. So, from the perspective of evolution, individuals are constant. Populations change. With a directional change in environment, yes, there is a "universal shift". In a climate growing colder, there is a directional shift in the character of the population toward longer fur. Now, that doesn't mean that all deer are born with longer fur. Instead, just as many deer are born with shorter fur as longer fur, but only the longer furred ones survive. Natural selection shifts the population over the course of generation. Any population has characteristics in a bell-shaped curve. In the case of our hypothetical deer, we would have a bell-shaped curve with a center (mean) of 1 cm length of hair (fur). But the range would be from, say, 0.5 cm to 1.5 cm. However, in the colder winter, only those deer with fur 1 - 1.5 cm survive. Thus, the next generation now has a new bell-shaped curve with a mean of 1.25 cm and a range of 0.8- 1.7 cm (you still get some deer born with shorter and longer fur). The next winter is even colder and only those deer with fur 1.1 to 1.7 cm survive. Now the next generation has a bell-shaped curve from 1.0 to 1.8 cm with a mean of 1.4 cm. Do you see how the population is changing over time? Yes, each generation still has individuals with 1 cm length fur, but we've lost all those deer with 0.5 cm and now have new deer with 1.8 cm. What we get at the individual is the variation within the population. And it is the variation that natural selection acts on. Natural selection acts on the individual, and an individual is either lucky or unlucky in the alleles it is dealt at birth. If it is dealt a set of alleles that do well in that particular environment, then that individual is selected. If not, then the individual -- and that set of alleles -- is eliminated. Since mutations are due to universal biochemical and chemical mechanisms, yes, the mutation rates are the same. And yes, the different studies have been done on Drosophila in widely separated locations: the US and Europe, for instance. And the results have been the same. Now, remember that the mutation rate was determined by looking at hundreds or thousands of individuals. Always in biology what you get is a mean ± the standard deviation. For the sake of simplicity, usually only the mean is reported, but don't be fooled. Basically, the mutation rate would be 1% ± 0.1. Which means that 2.5% of individuals will have a mutation rate < 0.98% and 2.5% will have a mutation rate > 1.2% Large changes are, as you say, usually accumulations of small changes. There are exceptions. If you have changes in the Hox genes -- control genes in development, you can have major changes in the organism. For instance, a change in the Manx gene makes a tail. And a change in just one nucleotide in the Ubx gene goes from the multiple legs of the millipede to the 6 legs of an insect. However, we have at least 2 ways of looking at "farther in time" in evolution. One is to look at existing related species and see the intermediate steps of evolution. A recent study looked at the evolution of the placenta and a genus of fish as a series of intermediate steps from species to species within the genus: David N. Reznick, Mariana Mateos, and Mark S. Springer Independent Origins and Rapid Evolution of the Placenta in the Fish Genus Poeciliopsis Science 298: 1018-1020, Nov. 1, 2002. http://www.u.arizona.edu/~mmateos/reznicketal.pdf News article at: http://www.sciencemag.org/cgi/content/full/298/5595/945a Another example is the family of skinks. The entire family is intermediate between lizards and snakes and shows the decreasing length of legs from lizards to snakes. And, of course, there is the fossil record. Sometimes the record is complete enough that there are series of transitional individuals (and enough individuals to do the bell-shaped curves) connecting large evolutionary changes. three such studies are: 5. PR Sheldon, Parallel gradualistic evolution of Ordovician trilobites. Nature 330: 561-563, 1987. Rigourous biometric study of the pygidial ribs of 3458 specimens of 8 generic lineages in 7 stratgraphic layers covering about 3 million years. Gradual evolution where at any given time the population was intermediate between the samples before it and after it. 1. Williamson, PG, Paleontological documentation of speciation in cenozoic molluscs from Turkana basin. Nature 293:437-443, 1981. 1. McNamara KJ, Heterochrony and the evolution of echinoids. In CRC Paul and AB Smith (eds) Echinoderm Phylogeny and Evolutionary Biology, pp149-163, Clarendon Press, Oxford, 1988 pg 140 of Futuyma. This one shows the diverging bell-shaped curves. There are many instances of observed speciation, some with quite large changes in characteristics of the populations. Actually, you do have such mathematical rigidness. The equations of population genetics derived from Mendelian genetics are very rigid and very deterministic. The studies you have read are not "organisms mutation", but natural selection at work. You are thinking of the peppered moth and the Grant study of the beaks of finches on the Galapagos. There you have directional selection within a cycling environment. IOW, you don't have the same environment but an environment that changed one way, and then went back. In the peppered moth the environment changed with industry and the darkening of birch bark with pollution. So natural selection picked the dark colored moths (whether by predation or some other mechanism) and the population shifted from mostly light colored moths and very few dark colored ones to mostly dark and very few light colored ones. Then the environment changed back before the dark color could be fixed and the light color eliminated. So the proportion of light to dark moths shifted back. In the Grant study, it's not as simple as it looks. Looking only at the gross size of the beaks, yes, the population shifted from small to large beaks and then back to small beaks. But looking at detailed measurements of shape, the new small beaks are not the same as the original. Yes, they are small again, but they are different. In experiments where the environment has changed and not changed back, natural selection has shifted the population and it has stayed there. A good example is this study: 1. Case, TJ, Natural selection out on a limb. Nature, 387: 15-16, May 1, 1997. Original paper in the same issue, pp. 70-73 (below). JB Losos, KI Warheit, TW Schoener, Adaptive differentiation following experimental island colonization in Anolis lizards. Nature, 387: 70-73,1997 (May 1) 1a. JB Losos, Evolution: a lizard's tale. Scientific American 284: 64-69,March 2001. Phenotypic plasticity and evolution of Anolis lizards. In this study lizards were introduced to various islands in the Bahamas. These islands had different types of vegetation -- different constant environments. The length of the limbsof the lizards varied from island to island 5 years after the introduction. The limb length varied according to the plant life present on the individual islands. Because the environment is constant, the change is constant.

Which is what I said. That's not fixation, it's elimination. Fixation is defined as EVERY individual in the population has the allele or trait. You are saying that NO individual has it. So, in this case the population genetics doesn't change, does it. The frequency of that particular allele was 0 before the possum was born, and it will be 0 in the next generation. But for the evolution of new traits to occur and populations to permanently change, fixation is required. So the essential part of genetic drift for evolution is NOT the elimination of individuals. After all, the equivalent of that allele or trait will occur again. And again. And again. What matters is whether the allele/trait can become fixed. See below for the odds of that and remember the odds of fixation for an allele/trait under natural selection. Sorry, but "a few thousand" is way to large for genetic drift to have an effect. Mathematics. Futuyma page 393 Kimura and then Li and Gauer derived the probability of an allele being fixed in the population. The probability of fixation of an allele A2 where the fitness of the genotypes are: A1A1 = 1, A1A2 = 1 +s, and A2A2 = 1 +2s is: P = 1 - e^2Nsq/1 - e^-4Nq where e = the base of natural logarithms = 2.718, N = effective population size (breeding pairs), s = selection coefficient, and q = the initial frequency of the allele in the population. For a mutation, q = 1/2N Where s = 0 (genetic drift) then the equation reduces to P = 1/2N. The influence on fixation is obvious. Double the population and you halve the probability. Any N > 50 really reduces P. At N = 50 (100 total individuals), p = 0.01 Now, for "a few thousand", say 3,000, P = 1/6,000! No, for genetic drift to have a chance of having an effect, you need N < 50. And most populations are not even close to that. We are seeing that now with some endangered species. Genetic drift is most likely to happen either at founder events or during extinction. If I remember correctly (and let me check this tonight), the number of generations required for fixation by genetic drift is 2^N/2. Look at this as N increases. For a population of even 2,000, that is 1.07 x 10^301 generations. For large carnivores, let's be generous and say that generation time is 3 years. That's 3.21 x 10^301 years! Since the universe is only 13 x 10^9 years old, it ain't never gonna happen.

At 20 years per generation and 150,000 years since H. sapiens appeared, that's 7500 generations. Quite a few but not all tht many. The problem is that, from a population standpoint, the pelvis isn't that bad -- most women survive childbirth and the survival of the child is even higher. IOW, altho the mother may die, the kid usually comes thru. So this is a tragedy for individual humans -- the woman and her mate -- but it is not a huge selection pressure. And pain in childbirth is an even lower selection pressure. Natural selection doesn't care if the woman is in pain, only that she has the kid. And the sex drive ensures she has the kid. Yes, women who have no pain in childbirth are going, on average, to have more kids. But it's going to take A LOT of generations for that to become fixed.

No. Neandertals and H. sapiens are both descended from H. erectus. We are sibling species, not ancestor-descendent. We, and neandertals, had trouble giving birth for the same reason: large head, small pelvis. From the news article: "The two teams basically agree, within their margins of error, that the evolutionary lineages of Neanderthals and modern humans split somewhere around 500,000 years ago. This fits with previous estimates from mtDNA and archaeological data" See? NOT ancestor-descendent, but two sibling species descended from a common ancestor. Neanderal and sapiens is analogous to chimp and sapiens, except the common ancestor is more recent.

Sorry, but that is not true. See the previous post and the equations therein. Genetic drift only operates if the population size is VERY small. Otherwise the number of generations it takes to fixation is simply way too long -- longer than the lifetime of the species by a couple of orders of magnitude. "neutral gene theory" is something different.

It's simple. It's the individual that is the object of selection, not the individual gene. So it is the package of genes that is the individual organism that is being selected. And that is the genius of natural selection: it can see the totality. As long as it has ANY effect, natural selection will "see" it. The equations of population genetics are very precise, and as long as the selection coefficient has ANY positive value, then the equations guarantee that, eventually, that allele will be "fixed" -- be in every member of the population. Here are the equations and, hopefully, they will help: Remember that, in the absence of any outside influence, such as natural selection, the frequency of an allele does not change from generation to generation. That is, if you have a population of 100 and 10 individuals have allele A and 90 have allele a, the next generation will be exactly the same: 10 A and 90 a. This is called the Hardy-Weinberg Law. Frequencies are symbolized mathematically by p and q. W is the relative fitness value. So we have W(A), W(B), and W(AB). The last is the fitness of the heterozygote in a sexually reproducting population. So, for the first generation the frequency p of A in the population is: p^2 +2pq + q^2. Straight Mendelian genetics. The frequency of p in the next generation after selection is: p' = p^2W(A) + pq W(AB)/p^2W(A) + 2pq W(AB) + q^2 (WB). Now, if W(A) and W(AB) are higher than W(B), it can be seen that p' will increase. You can see all this and a lot more in Chapters 4 and 13 in Futuyma's Evolutionary Biology, 1999. Remember Hardy-Weinberg. The frequency of an allele remains unchanged from generation to generation in the absence of outside influence. Therefore, the fitness of a new mutation is defined as the ratio of the number of progeny actually produced divided by the number of progeny expected by Mendelian genetics. This is going to be greater than one in the case of alleles with a survival advantage. From that we get a selection coefficient such that fitness = 1 - s. Now, doing the math we find that the advantageous allele A increases in frequency, per generation, by the amount delta p = (1/2)spq/(1-q). If you look at the equation, you see that delta p is positive as long as s is greater than 0, even if it is very small. Eventually p will equal 1, which means that every member of the population will have the allele. Thus, a characteristic with even a miniscule advantage will be fixed by natural selection. "Fixed" means every individual will have the allele.

Actually, it's 4 functions required for life: metabolism, growth, response to stimuli, and reproduction. And humans have already "created" entities that do these 4 functions. Or rather, they have discovered the chemical reactions that will make cells that do these. You will want to read Daniel Dennett's Consciousness Explained and Darwin's Dangerous Idea. Dennett does a thought experiment about a robot, which is perfectly plausible with current technology, that basically has free will.

I gave you the citation for your information. How old are you now? Don't you think you should do some library research so that you know what the current data is?

Still untrue. The evidence the scientific creationists used in the 18th and early 19th centuries is still there. It hasn't gone away. So what you still end up doing is getting into a contest with creationists on who can make the highest pile of "data for". Or you end up in a fruitless discussion about whether the evidence is "valid". Adding the word hasn't changed that you are still unconsciously using Mill's concept of "evidence", and that concept is fatally flawed. And thus your statement is fatally flawed as science. As I said, it's just bad science.

Please cite your quotation. I didn't say "explain the how", but hypothesizing a how. Those are 2 different things. Creationists say the "how" is instantaneous appearance in present form. When they say "don't need to explain the how", they mean that they don't need to provide a mechanism for that instantaneous appearance. And they are correct. After all, we don't have a "how" or cause for the Big Bang, the Big Bang is how the universe started. We don't have to "explain the how". Not entirely. Because creationism is a scientific theory. There are some statements science can't address. The existence of deity is one of them. Whether the universe is created by a deity is another. All science can say is: If a deity exists and if it created the universe, then these are the material mechanisms it used."

This seems to be the common ancestor of amphibians, reptiles, and mammals: 2. J A Clack, A new early Carboniferous tetrapod with a melange of crown-group characters Nature 394, 66: 1998 (July 2). 4. H Gee, Relics: The creature from the black lagoon http://www.nature.com/Nature2/serve?SID=64824792&CAT=Corner&PG=Update/update662.html Transitional fossil between amphibians, reptiles, and mammals.

In the sticky thread "Human evolution" the last post is mine tracing our ancestry thru transitional individuals to A. afarensis. There was a hypothesis advanced called the "aquatic ape" hypothesis. The hypothesis tried to account for our relative hairlessness by saying that one of our ancestors after our lineage separated from that of apes lived predominantly in the lakes and streams of East Africa, or in the adjacent Indian Ocean. It does not contradict Darwinism but simply hypothesizes how the species between the ape-human split and A. afarensis lived. The aquatic ape hypothesis has been discarded. It simply did not work and caused more problems accounting for our features than it solved. thanx

It's also a "why". Evolution is "descent with modification". And a "why" of the modification is natural selection. Another "why" is that there is more than one environment, so natural selection is the "why" is there diversity of species: to find designs to exploit the various environments. A third "why" is Mendelian genetics that ensures that characteristics are inherited. Basically, evolution is an inevitable consequence of living organisms. Unless there is only one way to earn a living, there is going to be evolution.

You misunderstood the book. The book was referring to the Miller-Urey experiments that used a simulated thunderstorm to show how amino acids and sugars could form from simpler molecules. One way to get life from non-living chemicals is here: http://www.theharbinger.org/articles/rel_sci/fox.html

Sorry, but that isn't true. As I pointed out, when you say "creation" you must also postulate a how. Depending on the "how", there can be quite a bit of scientific evidence! You have another problem. There is evidence for ANY and EVERY scientific theory, if that is what you are looking for. Yes, even evidence "for" young earth creationism. When you say "there is non [sic]", you are unconsciously invoking the inductivism of John Mill. Mill counted "evidence for" when that evidence could not be explained by any other theory. Unfortunately, Quine showed that, for any limited set of data, there are an infinite number of theories that can explain the data! So Mill's criteria doesn't work. This mantra "there is no evidence for creationism" is just bad science. And it hurts science in dealiing with creationists. In science, what counts is evidence against a theory. So, what you should be saying is: "there is data that disproves/refutes/falsifies creationism". And don't confuse "creationism" with "creation". That's another instance of bad science.

Talk to a Siamese twin and find out! Two brains, remember? From the article "It is the oldest known reptile to suffer from a birth defect known as axial bifurcation. This happens when an embryo is damaged, and some body parts develop twice." Too much retinoic acid at the wrong time during development is one way to do this. So this is not a species, but a birth defect within a species.