borbor@cuisun.unige.ch (BORIS Borcic) (06/25/91)
In a previous post, Larry A. Moran said : => =>Boris Borcic said, => => "As for justifying my statement that there is a bias towards the => molecular view, *without* assuming knowledge of biology other than => what is according to you, it is logically sufficient to note that => biologists [TM Moran] mean "evolution of molecules of lifeforms" => when they say "evolution of lifeforms". => Whether this bias is reasonable is all together a different question... => =>The word "bias" is insulting. To be accussed of bias is to be accussed of =>holding an UNREASONABLE or IRRATIONAL prejudice. Thus, there is no such thing =>as "reasonable bias". => =>When you accuse all biologists of bias [...] Well, sorry, I did not mean to be insulting. I did not "accuse" all and every biologist of bias, but the set of *present day* biologists *as a population*. Besides (and this seems to be a language problem) I intended "bias" very much the way you use the word "prejudice" above, that is, apparently, a word which does not in itself carry judgment about the attitude. See, in French, rationalists would tend to feel insulted if you accuse them of "prejuges" but would feel much more comfortable if you claim that the view they hold "temoigne d'un biais caracterisable". So, if it makes you more comfortable, swap "prejudice" for "bias" in all I have written. Better still, use "marked preference" (I can't convince myself that "prejudice" is not negatively connotated). On another hand, what I like about "bias" as I understand it is that it does not carry (meta-level) prejudice about the origin of the (base-level) prejudice. Do English speakers use "cognitive bias" or "cognitive prejudice" ? How is it in statistics. Does one speak of a "biassed estimator" or of a "prejudiced estimator" ? See, to me, saying that your viewpoint has a bias is like saying that your window has a location. Now you might live in the penthouse and enjoy a superior view, but that doesn't mean that you can see all I can see from my 3rd floor apartment's window. And unless this is the case, you can't deny my view is a possible source of useful information. Anyway, it is a pity that you won't discuss the existence of bias in biology. I am convinced there is much of interest to uncover. For instance, it is a matter of logic that a (scientific) world-view based on a quantity of factual knowledge should be independent of the order in which the bits of the knowledge have been acquired. On another hand, it is not clear at all that this is indeed the case for individuals, and even less so in the case of communities where the knowledge has accumulated in the course of generations, giving rise to heated debates and various schools of thought linked to specific subsets of the knowledge now available -- debates and schools whose traces very much condition the standards of communication of today. So the independance of the world-view from the order of acquisition can't simply be assumed without examination. In the case of genotype vs. phenotype, I would underline that for decades the genotype was the mystery, while the phenotype was by definition observable. Elementary problems given in introductions to genetics emphasize the notion that the phenotype is the given of the problem and that the genotype is the key to its solution, the real information, what you need to know to predict the outcome. An interesting thing about the phenotype is that it implies some form of observer (pheno- prefix means "to shine"). You may dismiss the view of the amateur who puts too much attention on phenotypical traits as an under-informed view, but doing so with too much emphasis you tend to bring in shadow the fact that the phenotype is a real participant to evolution in its own right, being what the environment distinguishes and selects (hence my reference to an "ecological process"), and not simply Mendel's puzzle. As a concrete (and well known) example, note how the prejudice towards a morphological definition of a species' identity is not confined to the eye of ignorant amateurs, but occurs also in the eye of predatory birds picking their preys among butterflys. What you dismiss as a stupid artifact in the eye of the human you have to take into account as a key feature of the process in nature. Furthermore, even if the (inheritable) phenotype is a deterministic function of the actual genotype, it is *not* an insignificant assumption that you could actually derive arbitrary phenotypical traits from the perfect knowledge of the genome - as your exclusive choice of genome-related variables (e.g. frequencies of genes in the population) in your *exclusive* model of evolution seems to imply. => =>Let's review the history of this exchange. You said that lack of morphological =>change is evidence that evolution has not occurred. I responded that evolution =>can occur at the molecular level and that morphological change does not have =>to be evident. I pointed out that the scientific definition of evolution is a =>molecular one. You responded by accusing all biologists of a bias towards a =>molecular definition! NO. You must be confusing me with the original poster who started the chain about "Coelacanth and evolution" - which would also explain that you replied to my two posts "Molecular vs. Ecological Evolution (was Re:.. " and "Convergence (was Re:..." resisting evolution in "Subject:" lines and restoring them to the original form. Almost the whole of our exchanges was included in the post you reply to, including the part I first reacted on with "...but isn't this a bit too dogmatic" when I thought I saw you state that morphology was irrelevent to evolution, that the only true measure of evolution is molecular and that evaluating evolution by the amount of morphological change is by consequence an error in all cases. To calm the flames, I can say that I fully agree with the formulation you now give to your statement, e.g. that evolution can occur at the molecular level without evident morphological change. =>Nobody accused YOU of bias ! No, not as an individual. "It is a common misconception among non-biologists..." I got a little heated at your throwing "hubris" at "amateurs who seem to assume they have (useful) insights" ... I don't know what "hubris" means except that it might sound like "you Boris", so I took this as an "ad nominem" attack even though it was not part of a reply to me :-) => =>I made a well-meaning attempt to educate you in an area with which I am very =>familiar and you are not. You respond by claiming that you are right and I =>am biased. There doesn't seem to be any point in continuing. I'm sorry that =>you react so negatively to criticism. => See above. By the way, the original poster you seem to be confusing me with did not _claim_ a position, he was _asking_ a question. My intervention, even as an antagonist to your response to him, cannot take the sense of a claim that the position in the original post was right, since there was no truly decided position in it. => => [...] Boris said, => => "I guess Peloxyma palustris is also easy to grow in the lab ?" => =>No, it is impossible to grow in the lab. The organism dies within a short time =>of being removed from its normal environment. There are only a handful of =>different samples that have been described. (Is there a point that you were =>trying to make?) => Not conclusively. But now I am really surprised, since I can't imagine an environmental condition that can't be reproduced in the lab in the volume of a couple centilitres that would seem largely sufficient to grow any single-celled organism. Unless, perhaps, it belongs to this famous hot water sulfur chain of the bottom ocean, or if it is a highly specialized parasite of some larger organism... but neither case seems to fit what "palustris" suggests... ? =>Boris goes on to say, => => [...] Hummingbirds and => Sphingidae. Adults of these two very specialized and extraordinary families => - as compared to their respective phylogenetical neighbors - display => a striking similarity in shape, size, locomotion, nutrition, and, => to a limited extent, thermoregulation and migrating practice. [...] => Now one is a bird and the other is an insect. What was their closest => common ancestor like ? How do their molecules compare ? => => If your model of evolution implies a state-space for species such that => common factors like the one between Sphinxes and Hummingbirds cannot be => evidenced, I'll say it is incomplete. => => If you tell me that such a model is the only one serious biologists would => consider (which I do not believe), I will say that biologists are not true => to observation." => =>The common ancestor of chordates and arthropods probably lived about 700 =>million years ago. It was likely a seqmented worm-like creature but it could =>have been unicellular. The DNA and protein sequences of birds and insects =>confirm that they separated about his time. In other words they are fairly =>closely related on an evolutionary scale. => (Thanks for the info) Depends on how you calibrate the distance; let me propose you one that, although baroque, is not completely unnatural -- and also topologically equivalent to your own, I believe. Divide the number of species that descended from the closest common ancestor (minus one) by the total number of species. Maximum distance is 1, minimum 0. Let me add to this that I agree that the amount of evolution in the early ages should not be underestimated, even if it left no trace -- and that the billion years it took are all together a good measure of it. One could say that half the distance was covered when sexual reproduction was first installed. But how to you define the frequency of a gene before the time of gene pools ? How do you define a gene before the genetic code was established ? Your definition of evolution implies both. =>Boris, in good faith, I do not understand your statments about "state-space" =>and convergence. Do you see convergence as a major problem for biology? =>If so please explain why. As far as I know the modern theory of evolution =>would not have any trouble with the example that you quote. => Do you define "trouble" by amount of gene sequencing yet to be done ? :-) Hmmm... Please admit for a second than this is indeed the way you define trouble. Then my belief is that the amount of trouble depends on what you want to show. If what you want to show is that the existence of phenotypical features common to *ONLY* Sphinxes and Hummingbirds is deducible from similarities in their genetic code, I think you are in a lot of trouble. I see convergence as a real problem, not so much for biology as a whole, but for the biology of evolution when *reduced* to the population-genetics model you advocate. In the case of Hummingbirds, there is evidence of an information flow going from insects to birds by which some birds inherited from insects characters they share with no other birds. The carrier of the information is not confined to the gene pool - the flow occurred well after the gene pools became separated. The carrier is the ecological interaction with flower plants. (And as far as flower plants are concerned, the Hummingbird is a late form of pollinating insect) (but not so, say, an owl). The state space. I guess the simplest population-genetics model one can imagine would abstract the gene pool to a single locus with two alleles. You would describe the dynamics of the pool using a single variable, say u, that expresses the relative proportion of the two alleles, varying with time t. The state-space is the set of possible (u,t) values, isomorphic to [0;1]x[0;T) -- T being the time at which the species disappears and the relative frequency of its genes becomes undefined. This is what comes to my mind when you define evolution as a change in the frequency of genes. Please correct me if I'm wrong. Now there is no way you can capture the fact of the common niche and adaptation of adult Hummingbirds and Sphinxes in a *single* mathematical model such as the one above using only genetic variables. On another hand, you might display the common niche with a careful choice of phenotypical traits variables that can be defined on both types of animals - and that are directly related to their common mode of interaction with flowers. =>-Larry Moran => => Regards, Boris Borcic - borbor@divsun.unige.ch