Instinct in Evolution

I do not consider myself a scientist of any sort... far from it; I am as reliant on layman's terms and dictionary references as a school child is when I come to this site. Please excuse any spelling mistakes, and needless to say, my grammar will not be anywhere near as scholarly as most of you are accustomed to. With that forewarning you may read what little I have to say concerning evolution. (Just to clear some things up: I am not a creationalist by the strict definition of this site, but I do believe in a creator, hence I do not consider evolution as explained within the confines of this website to be accurate.)Some time ago (a few years, if you want to get technical) I started to browse information on evolution. From the beginning I was prejudiced against it, because, honestly, I believed that infallibly, we had to have a creator. I have not had enough time to browse this entire website (would take me years with the time and attention span I have), but from what I have read, I would like to make some comments, and point out a fact, or interesting detail that might give most of you something to ponder.First, to those creationalists that try to read the bible at face value and apply it that way, let me suggest that you read: 1 Timothy 6:3-8... Apply this at your leisure and forget about trying to disprove a science with a book that was not made to debate science, but to talk about God. As for evolution, I should start by stating what I have understood that it means to most people in this site: Evolution is the natural progression of modifications that an organism goes through while adjusting to its environment. These modifications can take much time, or could happen within a few thousand years, but are not apparent in a human's lifespan, but the result over a long enough time span, is that the end product differs in appearance and functionality from the original organism depending on its environment. Yes, I know some will not completely agree with every phrase I said above... finding some inconsistency that they do not agree with because of the way I said it or something, but I am trying to condense a few thousand pages of posts into a sentence... so bare with me.Well getting to my point, I have noticed so many differing theories as to how an animal can make changes from one generation to the next, and how many similarities there are among them. Honestly, I do not know anything about that or how it works, so when you reply to this post, make it as understandable to me as I will make my own text understandable. One mayor point that I have not seem in any post, however, is how instinct plays a role in evolution.Every organism (from what I have understood) seems to come pre-programmed with a set of instructions on how to use every part of their body. There is nothing in evolution that states how those organisms get to have those changes from one generation to the next. Let me try to rephrase what I have just said, and give an example or two:(Pardon me for using complex creatures, but I do not know the workings of the simpler ones) Every year a school of fish travels thousands of miles to the shores of their birth, birds know to fly south, even though they have never been there, little newborn kangaroos and other animals born in pouches (it's embarrassing, but I don’t know what is the term for those) "know" that they have to get to a tit to survive. New born human babies cry for attention or when they are hurt. There is an infinite amount of examples in nature of how animals "know" what to do without having any prior "knowledge" to the fact (needless to say, we all have sexual urges). Even cells and smaller things have an "instinct" that they follow: phagocytes "sniff" out the chemical signatures of certain bacteria or viruses, and engulf them, further breaking them down into usefull components. Even viruses, which are not even considered alive while in their virus form, have a set of instructions that they follow and every part of them serves a purpose: the head to keep the genetic information, the neck to inject it to the host, and in some of them even a landing gear to latch on to the host.This "instinct" present in all animals is something that in the many pages I have read (maybe its explained in another I haven't seen?), no reference is found, or is just plain avoided. When a part in an animal is evolving, does the sperm or ovum also carry the additional information needed to use it? Does the animal carry something within itself that serves no purpose now, but that will help it in the future, and which he will immediately know how to use? Did the horned creatures know as they were gathering their horns that they would have to butt heads to prove genetic dominance over one another? Or did their genetics suddenly give them something to do with the horns that they had for thousands of years.I could go on with several examples. But what I have said should be more than enough to illicit a response from residents of this forum. Replies are appreciated, but I will frown upon those who pick on my lack of knowledge... I already understand I am not as versed as any of you.

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Did the horned creatures know as they were gathering their horns that they would have to butt heads to prove genetic dominance over one another? Or did their genetics suddenly give them something to do with the horns that they had for thousands of years.

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I think this line sort of sums up your argument, so I will focus on it. Your concept of evolution is a bit Lamarkian. Evolution doesn't work by things developing all at once in a full form - virtually everything works either by cooption or enhancement of existing functionality with parallel lines of selection of completely different traits.For example, rhodopsins are used in a number of organisms as chemical "triggers" - they relay signals in a cell to allow one particular stimulus or reaction to cause another. For example, you could have a rhodopsin stimulated by the presence of a nutrient source in the water that has the rhodopsin inhibit swimming. Well, it just so happens that rhodopsins can take forms that are additionally stimulated by light - these are known as photorhodopsins. What if the aforementioned rhodopsin became photoreceptive? Well, it would make the cell stop swimming if it had enough light - in short, it would coopt existing functionality, and now you have a light sensitive cell.Things like horns are no different. In fact, since carnivores of many types often go for the neck, even quadrapeds that are preyed on by such animals that don't have horns often try thrashing their head as a last resort to knock away the predator's lunges. The slow development of a bony crest that elongates and toughens the head would "coopt" this, and enhance its effectiveness; the crest separating into bony "horns" would save bone. Hardened hair projections follow the same selection rules.Other routes that could be taken include having a larger protected area, such as porcupine-style quills or stiff bristly hair that acts as armor, under which certain parts of the body that show themselves to be more at risk (such as the head) start being more protected than others. This then leads to a more proper motion control of the progressively more protected part being selected for at the same time. Note that this last case involves two separate traits - head motion and hair strength/distribution - evolving in parallel. Sexual reproduction makes parallel evolution even easier.Horns also need not have developed solely to ward of predators. If a population is stable and is not having trouble competing with other species, its biggest competition becomes its own species. Thus, species in such environments often begin to adopt flashier colors and other "disadvantages"; surviving with such a disadvantage indicates a high degree of fitness in your other traits. (for example, a bird of paradise's tail). Other species, instead of having traits that show their ability to survive predation, have adapted sparring for mating rights. A species that has already developed sparring, and is not having trouble competing for survival in its niche, can afford to develop biological tools (such as horns and antlers) that give it an advantage in its competition.

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"Illuminant light,
illuminate me."[This message has been edited by Rei, 01-06-2004]

Hi Absent Minded. Welcome to evcforum!Your questions are good ones. I think there's been some discussion on this board at various times, although I couldn't point to a specific thread.I would caution you that your question is borderline teleology. IOW, the way you stated your overall question on instinct reveals that you may be ascribing "purpose" to the non-learned behaviors we observe in animals. It is incorrect - or at least misleading - to say a kangaroo neonate "knows" to climb to a teat, for instance.Be that as it may, the simplified answer to your question is that gene-based behavioral traits (instincts) are no different than any other physical trait. IOW, they are operated on by natural selection working at the level of the individual organism just like any other phenotypical trait. Where things get confusing is how to differentiate between learned and instinctual behaviors, how much the genetic component drives the behavior vs how much the environment influences the behavior, etc. However, the nutshell answer is that instinctive behaviors evolve exactly like any other trait and via the same mechanisms.

Thanks for the welcome Quetzai. Rei, I believe you missed my point, as I was not refering to the method in which animals evolve in my post. Granted, by reading your reference on what is Lamarkian evolution, I see that it is not what is currently accepted. But, you sidestepped my point, and digressed into how animals evolved differing traits, and failed to note that I was talking about a more minute matter of the coding (if I may use the analogy) of this information and how to use it in generations to come. Quetsai was much closer to what I was trying to say and upon re-reading my own post, I realised that I placed more examples than information, but just to really clear things up, this is a little more to the point (and hopefully it will eliminate the guesswork as to what I am trying to get at):1. Each organism performs certain "instincts" that enable it to survive. (ex.: migration, courtship rituals, proper feeding of their newbornes, proper way to copulate)2. Regardless of where the animal is placed, many of these "instincts" still function, which means that it is coded into its DNA.My question stems from those 2 points, even though not by far entirely. Saying that "...gene-based behavioral traits (instincts) are no different than any other physical trait. IOW, they are operated on by natural selection working at the level of the individual organism just like any other phenotypical trait." - Quetsai, is just sidestepping my question as to HOW this is actually managed. IMHO I feel its is much easier to state that over time because of the enviorment certain characteristics, like growing of a horn, or sleakening of a shark happen, than it is to state the same about those types of "instincts", since they don't have the same chemical/biological backing.Rei stated: "... since carnivores of many types often go for the neck, even quadrapeds that are preyed on by such animals that don't have horns often try thrashing their head as a last resort to knock away the predator's lunges. The slow development of a bony crest that elongates and toughens the head would "coopt" this, and enhance its effectiveness; the crest separating into bony "horns" would save bone. Hardened hair projections follow the same selection rules." Is this the same procedure that Quetsai stated is followed when "instincts" are in play? Did birds ever have a different way of feeding their newborns, and over time, because of changes in their eating habits, they had to feed differently? And if so, how was this transcribed to the DNA? Did some of them just come already adjusted and henced survived the next generations? ... I digress.. and have given to much information... which means that some more confusion might arise to what I am stating. I will leave this information here and post again tommorow in response to those who answer. I do thank Rei and Quetsai for their promptness.

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IMHO I feel its is much easier to state that over time because of the enviorment certain characteristics, like growing of a horn, or sleakening of a shark happen, than it is to state the same about those types of "instincts", since they don't have the same chemical/biological backing.

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My apologizes if I misunderstood you; I thought your question was about whether two traits (such as instincts and a physical trait like a horn) can evolve at the same time. Your question appears to be more about whether instincts can evolve at all - am I correct?Assuming that is what you meant, we should look at other cases of complexity from simplicity. First off, are you familiar with flocking and schooling algorithms? (if not, I can provide some references). Basically, they demonstrate examples of how seemingly quite complex behavior can emerge from *very* basic rulesets. They key is just determining the rulesets for a particular desired behavior. Neural nets are exceedlingly good at storing such arbitrary rulesets. The layout and timing properties of such as neural net are coded in the DNA, just as most physical and structural traits are.

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"Illuminant light,
illuminate me."

It most assuredly wasn't my intent to "sidestep" your question - something that I have never done on this forum, at least. I answered what I thought you had asked. Apologies for misunderstanding you.As to the "how it's managed" question, there are quite a few answers, depending on the organism and the behavior in question. Sexual selection, kin selection, optimal foraging strategies or other optimization rules, Muller's Ratchet, social interaction strategies, competition, habitat selection, niche construction, etc, are all natural selection mechanisms which operate on genetic traits that influence behavior. It works pretty much the same way as selection for longer legs. Behaviors vary within a population just like any other phenotypical trait. If a behavior allows the individual organism greater success in survival and/or reproduction than other variants, it will be selected for.One of the better references I have on my shelf which discusses a pretty comprehensive list of models and discussions of behavioral adaptations is Krebs JR, Davies NB 1993 "An Introduction to Behavioral Ecology", Blackwell Scientific Publishers. One of the things that Krebs brings out is the fact that behavior can effect the evolution of morphology by either conserving traits or intiating adaptations to new ecological niches, etc. You might find the book interesting.Let me know if you need more specifics.

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IMHO I feel its is much easier to state that over time because of the enviorment certain characteristics, like growing of a horn, or sleakening of a shark happen, than it is to state the same about those types of "instincts", since they don't have the same chemical/biological backing.

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The neurological system and the skeletal system stem from the same thing, DNA. Instincts, such as natal imprinting or seasonal migrations, are hard-wired into the brain. It is not a learned behavior like tool use or mamallian predation, it instead closer to a reflex but centered more closely to the emotional center of the brain. Someone please correct me if I am wrong, but I believe the Limbic system in the brain is responsible for most behavioral instincts.So, maybe the question to you is, if DNA can code for skeletal structure and muscle development, why can't it code for neural networks in the brain that give rise to instincts? And also, why can't the DNA coding for instincts be open to random mutation and selection like the rest of the DNA molecule? And thirdly, what part of the brain is NOT run by chemical/biological mechanisms like the rest of the body?

I think he's asking what the biochemical basis for behavior is. Basically, how do you get from a gene that codes for an instinct or behavior - like alcoholism or homosexuality in humans, or sexual display in birds - to the actual expression of the behavior by the organism?That's a good question. I imagine the answer is pretty complicated, and involves such biochemical signaling compounds like hormones and neurotransmitters. I doubt that there's a simple, universal answer - how you get from gene to action very likely is specific to each instinct.

Crashfrog brought out the point I was trying to get at. Now that its in terms that you all recognise, I want to make my second point, but not before setting a little basis for evolution once again, since I thought (incorrectly) that Lamarkian Evolution was the accepted type of evolution here. This is what I have understood evolution is:Evolution is a process in which natural selection, random mutation, and chromosomal differences take part in shaping the outcome of the next generation ussually in such a way as to be inpercievable to the naked eye. It is not "purposefull" as genes have no will of their own, but it is continuous so even today it is still ongoing.I understand that this definition is also lacking by most standards in this site... but hey, I am getting there. Please refrase my definition if you feel I am missing something, or if I have phrased something inapproprietely. Let me get then to a few points that came up when I was thinking about the defenition above:1. "how you get from gene to action very likely is specific to each instinct." Crashfrog.2. Mutation seems to be the only way to effectively change a gene, while Natural Selection and Chromosomal differences just move around what is already there.So...3. Behavior should eratic in some members of the population as a result of a "random" mutation on the genes that effect behavior.In fact... and I know I should stop in the above point but... it should be the case that since each generation is only affected by mutation of the genes, that this definition of evolution is flawed, for it only allows for random mutations to add content to the genes while natural selection and chromosomal flips and duplications and whatever other type of interaction, just work with what is already existing. ... I understand that this type of terminology was probably already dealt with here, but please be mindfull that I am not an expert, and I have not been able to browse every subject in these forums.I thank all who have replied till now, and I have prepared my mind to be "royally buttwhooped" by those who have more knowledge than me and are willing to share. :-P

Hi AM:Although it's possible to quibble with the wording, you are substantially correct in your definition of evolution. So I'll content myself with discussing this bit from your post: To quote Paul Ehrlich: "Genes do not shout commands to us about our behavior. At the very most, the whisper suggestions, and the nature of those whispers is shaped by our internal environments (those within and between our cells) during early development and later, and usually also by the external environments in which we mature and find ourselves as adults." ("Human Natures", Penguin Science 2000, pg 7). Although he was talking about our own species, his statement makes a pretty fair point of departure.I'm going to back up a tad here. There are in fact two general types of behavior: instinctive, and learned. The first type consists of acts that every individual of a given species is able to perform without first having to experience them performed by others, and without being in any way guided or instructed in them (a mother rat will build a nest and groom her young even if she is raised in total isolation and has never seen other female rats engage in those acts). Instinctive behavior is the only type directly effected by random mutation (obviously), because it is hard-wired into the genes.The other type of behavior - learned or acquired behavior - consists of acts that appear to be influenced by an animal’s own particular experiences. This type of behavior is where we can see sometimes significant differences in individuals of the same species or even within the same population. Although acquired behaviors may have a basic genetic component, they are in general manifestations of and heavily influenced by the environment in which the individual finds itself.Crash is completely correct. There is essentially a continuum on which both any particular behavior or any particular organism can be placed that runs from "entirely instinctual" to "entirely acquired". To grossly oversimplify: the more complex the behavior, the more environmental influences shape it; the more complex the organism, the larger and more complex becomes the suite of behaviors it has available, and hence the more "learned responses" come to predominate. A honeybee has a very limited set of hard-wired responses to environmental stimuli. A human, OTOH, has a wide and extraordinarily complex suite of possible responses to a given situation - almost all of which are either acquired OR are heavily overlain with acquired response patterns.What is interesting is that, although both types of behavior can be influenced by environmental factors, genetically "programmed" responses can only be changed by natural selection operating over evolutionary timescales - and changes can only be passed on through reproduction. Acquired behaviors can be changed by natural selection - taken in its broadest meaning - in a single individual's lifetime, and can not only be passed on to its progeny, but also passed laterally to other living members of the population/species. The evolution of learned behaviors can be extremely rapid.

That sounds like an accurate description of the process of evolution. I'm not sure what you think is "flawed" about it; there's substantial evidence that a process that combines natural selection pressures on the results of random mutation can give rise to considerable novelty and complexity. There's no need for any other magic process that adds information to genes; random mutation is sufficient. Sure - keeping in mind that it might be impossible to distinguish between the nominal range of "normal" behavior and a truly erratic deviation because of mutation.

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Behavior should eratic in some members of the population as a result of a "random" mutation on the genes that effect behavior.

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Sure - keeping in mind that it might be impossible to distinguish between the nominal range of "normal" behavior and a truly erratic deviation because of mutation.

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Also keeping in mind that most mutations are very minor. Evolution doesn't "leap forth", even during punctuated equilibrium; the most "rapid" evolution still typically takes several thousand generations. It's not like a protein starts to fold differently and suddenly you have twice the visual acuity that your species had before or that a new amino acid gets inserted into a sequence somewhere and an animal suddenly develops with fins and gills. The same holds true with the properties of the mind's development and functionality.That is an important thing to remember. Because evolution doesn't just "leap forward" (that would almost never work - the probabilities are just too low), all evolutionary paths have to be *continuous* - i.e., there must be a progression of tiny steps in which each step leads to a more advantageous result given the current environment that the species is living in. Most evolution results in steady states, or "plateaus", in which, if the niche hasn't changed much, evolution slows or even stops. In such cases, the species simply "run out" of advantageous changes to make. However, every place on Earth is constantly changing, and this forces niches to change - often dramatically. And a change in one small regional area can lead to changes in the balance of other areas as well (as species migrate outward, the environment changes, rivers change their content, etc). Whenever the niches change, evolution begins on the template of the species that came before, with new selective factors - but again, constantly requiring that the changes all be small, with no sudden leaps.Here's an example: picture that you're some sort of immortal animal breeder, and you're trying to breed animals for top speed. You take a group of cheetahs, and only breed the fastest males. After several thousand generations, your cheetahs will be going quite fast; perhaps their legs will be longer, their metabolism faster, their lungs larger, etc. The new cheetahs would do poorly in the wild because of their increased food needs, reduced maneuverability, and the other things that suffered from your new selective factor - but they'll be *very* fast. Eventually, however, they'll stop getting faster, and end up pretty much in a steady state (we've seen this happen, to a large degree, to horses; horse speed gains have greatly slowed in modern times).However, what if you then took an eagle that was slower than the cheetah to begin with, and started breeding it for speed? The eagles would get their best speed while diving, and you'd start getting larger and larger birds that are more fit for diving; before long, you may have eagles that are going as high as 200 miles per hour, far surpassing your cheetahs in speed. The cheetahs had reached the fastest possibilities of *their* evolutionary line given their current "niche" (speed-selective), but they weren't the fastest species possible. Your eagles, which started with a different biological "template", had the capability to reach much higher speeds after selection. Yes, the cheetahs could suddenly go to light-boned, light-bodied feathered animals with enough mutations, but that breaks the critical rule: evolution occurs only if there is a smooth path of small changes for which each is advantageous. To approach being like an eagle, the cheetahs would have to first reduce their land speed, which is selected against.I'm not sure if this helped... I'm just trying to help you get a better grasp on the concept, since you seemed to be having some trouble with it.

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"Illuminant light,
illuminate me."

Very good... now that we seem to have come to a certain understanding as to what evolution is, and many have presented their cases as to what is, and what is not possible, here is my third, and probably final point in this discussion (get paper and pen ready, this is going to do a few flips before it falls):Premise (Evolution) 1. Evolution is a process in which natural selection, random mutation, and chromosomal differences take part in shaping the outcome of the next generation ussually in such a way as to be inpercievable to the naked eye. It is not "purposefull" as genes have no will of their own, but it is continuous so even today it is still ongoing.By addition 2. "There are in fact two general types of behavior: instinctive, and learned. The first type consists of acts that every individual of a given species is able to perform without first having to experience them performed by others, and without being in any way guided or instructed in them (a mother rat will build a nest and groom her young even if she is raised in total isolation and has never seen other female rats engage in those acts). Instinctive behavior is the only type directly effected by random mutation (obviously), because it is hard-wired into the genes." - QuetzaiBy inference and addition. 3. "...genetically "programmed" responses can only be changed by natural selection operating over evolutionary timescales - and changes can only be passed on through reproduction." QuetzaiThen this point comes in.. and at least in my mind, just shatters what has been stated above... correct me if I am wrong.. and please follow my logic:4. "...evolution doesn't just "leap forward"... all evolutionary paths have to be *continuous* - i.e., there must be a progression of tiny steps in which each step leads to a more advantageous result given the current environment that the species is living in. Most evolution results in steady states, or "plateaus", in which, if the niche hasn't changed much, evolution slows or even stops." - ReiFirst of all, I am assuming that Rei's comment is a reflection of the thoughts of most people that have commented so far. As to why I see this comment as a tripping stone for evolution and why I said in a prior post that The current definition of evolution is flawed, here is my logic:1. Behavioral genes are very complex: "...how do you get from a gene that codes for an instinct or behavior - like alcoholism or homosexuality in humans, or sexual display in birds - to the actual expression of the behavior by the organism? ... I imagine the answer is pretty complicated, and involves such biochemical signaling compounds like hormones and neurotransmitters. I doubt that there's a simple, universal answer - how you get from gene to action very likely is specific to each instinct." - Crashfrog2. "There are in fact two general types of behavior: instinctive, and learned. The first type consists of acts that every individual of a given species is able to perform without first having to experience them performed by others, and without being in any way guided or instructed in them (a mother rat will build a nest and groom her young even if she is raised in total isolation and has never seen other female rats engage in those acts). Instinctive behavior is the only type directly effected by random mutation (obviously), because it is hard-wired into the genes." - QuetzaiNow here come a few critical points:Starting from Quetzai's example of the mother rat and her nest: at what point in history did that type of mammal's nest building originate? Note, that I do not mean that it suddenly came about, but what instint, if from an already existing one, got molded into bringing in surrounding materials and using it as incubators for its new-born? How far back do we have to go, to notice that there was a point in which nests were not as they were today, or in which nests did not exist whatsoever, cause the random mutation within the instint had not started.Let me not continue that train of thought up there and move on to another point. If "evolution is continuous", that would mean that every organism, without exception, has vestigal instints (remnants of prior instints that at one point were usefull, but as a result of lack of use, have faded away). More-over, every organism should also have evolving instincts... an array of instints that have no purpose, but that do not hinder them. I am no expert in animal behavior, so if anyone is, please post your thoughts. If vestigal, or evolving instints are not found in nature, then the current concept of evolution, as I said before, is flawed.Due to my lack of time, I will not be able to finish this post today (after all, I am a working man, and I do this when I have a little time), but what I have said so far should get you an idea of what I will be getting at in the examples that I will state when I come back. Any input is welcome, and Rei: I get a handle of things pretty quickly... I just don't remember them too well :-P

Not exactly. How would you detect a vestigal instinct in an animal? How would you detect the presence of an instinct that the animal is ignoring?It looks like you're about to complain about the lack of observation of something you've defined as essentially unobservable.You might have an argument if we knew which genes corresponded to which instincts. But the only way we infer the genetic basis of instinct is through observation of said behavior through an organism's decendants. Therefore there's no way to tell the difference between an organism with "broken", vestigial instincts and an organism that simply doesn't have a given instinct.

You missed a rather key point in your resume of the discussion. To wit, that expressed behaviors in complex organisms are heavily influenced by environmental factors. Indeed, there is no sharp dividing line between instinctive and learned (which is perhaps a bad term — maybe environmentally variable gets the point across better) behaviors.Scientists know by direct experiment that many behaviors are controlled or influenced by hormones. In nest building, for instance, they know which hormones are responsible — estradiol among others (see for example Cheng, M-F., and Silver, R. 1975 Estrogen-progesterone regulation of nest building behaviour in ovariectomized ring doves (Streptopelia risoria), Journal of Comparative and Physiological Psychology, 88: 256-263 and Negatu Z, McNitt JI. 2002 Hormone profiles and nest-building behavior during the periparturient period in rabbit does, Anim Reprod Sci. 72:125-35). They know what genes are responsible (see for example Walton SL, Burne TH, Gilbert C 2002 Prostaglandin F2alpha-induced nest-building behaviour is associated with increased hypothalamic c-fos and c-jun mRNA expression , J Neuroendocrinol. 14:711-23). Finally, they know what environmental triggers change or initiate the expression of these genes (see for example Noirot E. 1974 Nest building by the virgin female mouse exposed to ultrasound from inaccessible pups Anim. Behav. 17:340-349 or V. Patin , B. Lordi , A. Vincent , J.L. Thoumas , H. Vaudry , J. Caston, 2002 Effects of prenatal stress on maternal behavior in the rat, Developmental Brain Research 139:1-8). They have even shown how natural selection can modify behaviors (see for example Sluyter F, Bult A, Lynch CB, Van Oortmerssen GA, Koolhaas JM 1995 A comparison between house mouse lines selected for attack latency or nest-building: evidence for a genetic basis of alternative behavioral strategies. Behavior Genetics 25:247-252). IOW, all of the elements necessary for natural selection to operate on instinctive behaviors are in place: any phenotype — including behavioral phenotypes — that provides a net increase in the organism’s fitness will ultimately (all other things being equal) be fixed in the population as the frequency of genes for the behavior increase in the population over the generations. Since a nest increases the survival (and hence reproductive fitness of the mother) of offspring, efficient nest building is an easily understood evolutionary adaptation. Rats especially, since their neonates are completely helpless and can’t even thermoregulate. Any rat that didn’t have the appropriate nest-building behaviors would of necessity leave less living offspring, and hence a smaller genetic contribution to future generations How far back? Who knows? Behaviors don’t fossilize, so direct evidence is lacking. We can know what and how, but not when. For much the same reason, it is extremely difficult to discern the earliest basis of a behavior (or a physical characteristic that doesn’t fossilize, for that matter). In any event, you’ve missed another key element that I briefly brought up in my previous post: behavior can effect the evolution of morphology. IOW, selection for the genotype can follow selection for the phenotype, at least with behavior. See, for a nice discussion, Murphy SK and Jirtle RL, 2003, Imprinting evolution and the price of silence, BioEssays 25:577 — 588. There is a feed-back loop involved here which leads to speculations of the chicken or the egg kind. Did the behavior come first, or did the genetic basis for the behavior arise and then drive the change in behavior? Impossible to tell: we know we can change some behaviors by changing the genes; we can change behaviors by changing the environment; we can change the genes — slowly — by changing the environment. So which drove what and when is probably impossible to discover. There is quite a lot of research going on now to try and specifically answer that question. For a nice overview of current thinking, see Schneider SM, 2003 Evolution, behavior principles, and developmental systems: a review of Gottlieb’s ‘Synthesizing Nature-Nurture: Prenatal Roots of Instinctive Behavior’, Journal of the Experimental Analysis of Behavior, 79:137—152. The TOE may be flawed, but this is certainly not a valid criticism of it. At best, it could be a serious problem for genetic determinism — a tiny component of the theory which is about as dead as a doornail anyway, given what we now understand about the false dichotomy of nature vs nurture. However, this isn’t my field, so I have no specifics to argue with you about. Tell me, how would you go about identifying or even defining a vestigial instinct? Or for that matter, an evolving instinct? After all, behavioral variance is quite common in natural populations, which is one way mechanisms like sexual selection can lead to evolution. Moreover, not all behaviors are adaptive — especially learned ones in more complex organisms like humans. In fact, some behaviors may be maladaptive if the conditions change. Perhaps you could give some examples of what you would expect to see in a vestigial instinct?Note to Adminmoose: Is that enough referencing, or do you want more?