A bird builds a nest. A beaver builds a dam. What is meant by calling such complex behaviour in animals “instinct”? Is it to suggest that no significant component of the behaviour is learned?
If so, where are the details stored? It seems incredible that “here’s how to build a dam” is encoded as such in the genes of beavers. But it’s also incredible to imagine Dam Engineering 101 delivered to beaverlings.
What’s the straight dope on instinct?
I am just a layman here but I’ll start the ball rolling. In animals low on the intelligence hierarchy, like ants, it seems to be clear that some behaviors are hard-wired into their genetic material. OTOH, some behaviors that are more complex in primates have been shown to be learned and described as “culture.” Cats in the wild teach their offspring to hunt, and IIRC when wild cats are raised by humans they do not naturally know how to hunt. Beavers and dams may fall somewhere in between.
So there appears to be a spectrum of behavior here. For all I know there may be some genes responsible not for a behavior itself, but for the ability to learn behaviors. You know that human children are just sponges when it comes to learning and are very imitative of adults. No reason to think that this trait doesn’t exist to some extent in other animals.
An instinct is a complex, unlearned behavior. Like anything else that’s passed on, it’s passed on genetically (unless there’s some other, unknown mechanism of heredity).
True. But that’s small beer compared to the multi-generational migration instinct encoded into monarch butterfiles.
So what is the method of encoding these behaviours? How do such things evolve?
Bonus Q - what behaviours in humans are instinctive ones?
We don’t know how hardly any higher behaviors are included in the brain at all. The state of brain sciences is very primitive compared to what most laypeople think it is.
Suckling and gripping, apparantly.
Ooooh, one of the hard questions.
The problem most people have with instinctive behaviours is the problem creationists commonly have with physical structures: they tend to look at it from the perspective of the completed whole, rather than as a process that builds on itself.
The behaviour itself is usually encoded as a series of appetitive behaviours. You know how when you get hungry you go looking for something to eat? You don’t need to consciously need to recall when you last eat or whatever, you simply get a feeling of unease that goes away when you eat something? Instincts seem to encoded using pretty much the same system. In fact you could make a reasonable case that seeking food is an instinctive human behaviour.
I know that doesn’t answer the nitty gritty of your question about how it’s encoded, but the fine details of how appetitive behaviour works is both complicated and largely a mystery (now there’s a surprise in neurophysiology). In simple terms animals are brain with neurons that are grow towards other neurons in such a way that they trigger that feeling of unease when certain stimuli are sensed. Those stimuli can be internal, as in a drop in blood sugar, or they can be external, like the sound of running water.
So how does a complex instinct like dam building evolve? Well it’s all speculative, but you need to accept in the first place that nest building evolved. We can go into how nest building evolved later if you want, but for now we need to accept for now that various rodent species around that worked have all evolved to build nests.
At some point some rodent, probably something like a muskrat, produced a mutation that led it to feel more at ease when it built its nest on the water’s edge. Because being on the water’s edge also meant that predators could only approach it from one direction that mutation also gave a survival advantage and multiplied. Once building near the water became genetically fixed it wasn’t terribly hard for a mutation to occur to build near running water. Why exactly that gave a survivival advantage is speculative, perhaps running water made it harder for predators like foxes and owls to hear the animal entering and leaving the nest, maybe it dispersed the odour, confusing tracking predators.
From there we get a series of similar jumps. Some animals developed mutations leading them to fele uncomfortable with water running into the nest, leading to waterproof nests. When those animals heard running water they built the nest thicker around it. That in turn was displaced to water running past the nest. And of course once you start stoping water running past the nest you have a dam. Building a dam in itself is a survival advantage, so although the original behaviour of stoping water flowing past the nest was an abberation, a displacement of the original function of making the inside of the nest watertight, it was advantageous enough to survive and get passed on.
The thing is I guess that the behaviour itself isn’t any more conscious than your hunger. You are consciously aware that you are hungry but you don’t consciously get hungry. Similarly if a beaver even starts to build a nest on a hilltop will not consciously decide it’s the wrong place to build, it will just get a feeling of unease akin to hunger. That will cause it to stop. When it builds lower down the slope the feeling abates slightly, and only goes away totally when it builds in a flowing stream. Similarly a beaver that hears running water isn’t consciously aware his dam is leaking, he simply feels very uneasy when he hears that sound and that unease is only lessened when he starts poking sticks into the area the sound is coming from. It only stops completely when the sound stops.
That is a debate in itself. As I said earlier we could make the case that seeking food is instinctive. It’s complex behaviour that we don’t need to learn.
But really it all comes down to hair you care to define an instinct vs a reflex versus a pattern of behaviour. Humans instinctively sleep at night, but it’s not strictly an instinct because it’s not complex enough. Infants instinctively trun when you brush their cheek, but it’ not strictly a reflex because it’s not complex enough.
If humans do have instincts they can all be overridden so easily by our conscious brain that it is almost impossible to prove.
If that gibberish is in simple terms you don’t want to know about anything complicated.
“In simple terms animals brains develop via neurons that grow towards other neurons in such a way that they trigger that feeling of unease when certain stimuli are sensed.”
Make more sense?
Not necessarily. Pair bonding, and a lot of the activities that go with it, are very likely instinctual and are very hard to override.
Years ago, I heard a biologist (It think on a Nova or Nature special) admit that when we say such and such a creature performs such and such an act “by instinct”, that’s shorthand for “we have no idea how they know how to do it”.
If they are ‘very hard’ to override it is hard to explain why the vast majority of humans that have ever existed did not form pair bonds. Monogamous pairs are a very, very recent invention. Throughout human history the norm was ploygamy, and often serial polygamy.
As I said, if pair binding is instinctiveit is so easily overridden by the conscious brain that it would be almost impossible to prove.
Smiling when being paid attention is instinctive - babies blind from birth will smile when their parents talks/plays with them.
What about instinctual group behaviour, specifically the tendency of us h.sapiens to organize into hierarchies?
Anybody who has ever cared for a newborn knows that babies instinctively root for milk and latch onto a nipple (although some aren’t that good at it and need some help).
IMHO as a layperson in biology–no, not even a layperson, just an observer–is that self-preservation is a strong instinct in people, as well as seeking sex. Your parents might have to teach you what is dangerous, because most dangers faced by the average person in 2006 are man-made. But people have what is typically called the fight-or-flight response to danger, which is an autonomic physical response, not a learned one. And I guess you pretty much know about sex. 
Thanks for the thought provoking reply. I wonder, though, if we must reach for mutation and genetically encoded “comfort” building near water.
I remember in grade school the old joke:
Bill: You know, Bob, back in prehistoric times women were responsible for caring for the young, clutching babies close to their chest. That’s why girls today in school carry their books in front of them, holding them with both arms. Men, though, were responsible for hunting food, primarily with spears. That’s why guys carry their books one-handed at their side. How do you carry your books, Bob?
Bob: In a back pack.
While I chuckled at the setup/misdirection of the joke, the “explanation” troubled me until I thought through the implications of social inertia. These ideas especially crystalized when considering the experiment with the monkeys, bananas, and the water hose (that I first heard in a motivational seminar at work). The experiment goes like this:
A group of monkeys are comfortably placed in a spacious cage with lots of trees and stuff. In the centre of the cage is a high ramp. Occasionally the experimenters would place a bunch of bananas at the top of the ramp. Eventually Curious George would ascend the ramp and partake of the bananas. Whenever this happened, the remaining monkeys would be harmlessly but uncomfortably hosed down with cold water, while the elevated banana muncher remained untouched.
Eventually the monkeys learned what the deal was. Whenever bananas were placed on the ramp, the gang physically restrained any monkey attempting to climb the ramp. Once it reached a point where the bananas were never touched, the experimenters would take out one monkey and replace it with another. The new monkey didn’t know the “rules” concerning the bananas and would try to climb the ramp when the bananas appeared - getting the monkey juice beaten out of him in the attempt, eventually learning to leave the bananas alone. No hose was required.
The experimenters would then take out one of the original monkeys, replace with another newcomer, wait for this one to be “trained” then repeat. Finally the entire population was composed of monkeys who had never experienced the hose. Nonetheless, they beat up any monkey who tried to reach the bananas - without ever fully understanding why the bananas were bad in the first place.
So, to my point: This provided me with the mechanism of how ancient practices translate into book toting behaviour - not literally, of course - but I wonder how much of this cultural, vestigal inertia is responsible for animal instincts, including in humans.
I wonder how true this is, that instincts can be overridden. Rather, yes it’s true, but I wonder how likely it is to happen in any one individual, or even less likely in groups (nations?) My suspicion (with no evidential basis for saying so) is that many of our instincts play out as rationalizations, i.e. something in us “wants” to do that instinctual thing, but we convince ourselves we (individually, tribally, nationally) that this is the reason we do it.
Back to the beaver: dunno if this is true, but I’ve heard that beavers will push sticks and mud up against a speaker system set up in the bush playing “river sounds.”
Nature’s Call you do realise that the story about the monkeys and the bananas is made up, right? It’s a joke. You were just using it to illustrate the point weren’t you, not as actual evidence?
As for your question “how much of this cultural, vestigal inertia is responsible for animal instincts” we can safely say that inmost cases the answer ins “None whatsoever”. This is very, very easily proved simply by raising a young animal in a cage with no parents. That way they can’t pick up any ‘cultural’ traits whatsoever.
A bee raised in this way for example will still build cells, spiders still spin webs, birds atill build nests and so forth. Quite obviously a creature that has never even see a member of its own species can’t be acting on any ‘cultural’ information. Any behaviour it engages in must be either instinctive or (highly improbably) self-taught.
I don’t know of any experiments involving rasing beavers in isolation in that manner, but I am confident that if you did they would still build dams exactly the same way as beavers have always done.
That might be defensible if there were any universal human actions, but there simply aren’t any. Aside from such broad categries as ‘toolmaking’ and ‘language’ no human action or behaviour has been common to every location and every culture throughout history. So quite obviously people don’t just rationalise there instinctive behaviour. If they have instinctive behaviour many people aren’t engaging init at all, ergo they have overruled the instinct.
If what you suggest were the case then all societies would have the same behaviour, but with different rationalisations. Instead we see that all societies have different behaviours. Therefore we can safely conclude that any instinctive behaviour can be easily overruled, assuming they exist at all.
I have no direct knowledge one way or the other of the truth of the monkey story. The situation it describes, though, is at least plausible - and merely leads me to wonder to what extent “social inertia” plays in what we call instinct.
I find that fascinating. It is without challenge or attempt to refute that I ask: do you have a cite?
I was thinking more along the lines of sex drive, hunger drive, some addictive behaviour, and hierarchical social arrangements. Ants and bees seem instinctually to arrange themselves hierarchically. So do humans. Do we do so as an expression of something “instinctual”?
There are much in common, though - namely the few I mentioned along with the ones others mentioned (e.g. smiling). Again - not arguing with you, just trying to understand.
Point of order: I’m not arguing from any viewpoint - just throwing out thoughts to see what those who know more think about them in an attempt to answer the OP question (perhaps I should have placed this in GD). I have no problem accepting the idea that high-level behaviours are indeed encoded, and the result of evolutionary forces. I just don’t have an internalized understand of how that can be. My limited understanding of genetics suggests that genes contain instructions for protein production - these proteins assemble in ways we don’t fully understand to create an organism. I wonder by what mechanism behaviours of that organism are thus dictated.
This sort of thing is so common that the most basic web search will return enough material to keep you busy for a year.
Those things are not instinct, they are drives. An instinct is a behaviour, not a driver. Thus while all humans have the same hunger drive they don;t behave in any way similarly when attamnptin to satisfy that drive. Some hunt, some gather plants, some eat and kill their neighbours, some milk horses and so forth. The drive may be common but no resultant behviour is common, thus any instinct that is common must be easily overridden.
The vast majority of human societies had no herirachical social arrangements. That is found almost exclusively in agricultural societies. Once again, if such a thing is instinctive it was easily overridden by most of the people who ever lived.
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Smiling is far to simple to be considered an instinct.
That’s about right.
Largely via that actions of hormones. Some of those hormones are proteins, some are assembled by proetins. Hormones cause the neurons in the brain to grow in certain directions and form certain connections. It is largely the connections in the brain that determine bnhaviour.
Looked at that way it’s not so complex in principle.
I’ve read the theory that humans lack instincts because instincts became redundant or couterproductive once we developed advanced enough brains. A bird which, through mutation, lacks the instinct for hunting is SOL, but a proto-human (or proto-cat, presumably) which lacked the instinct for hunting could survive by imitating its parents. At the least, this makes the genes encoding hunting behavior unnecessary, which may be advantageous in itself if it frees genetic, developmental, or mental resources that can be used differently. A brain not hardwired for hunting may require fewer calories to develop, or may be more flexible and useful–which would allow still more instinctive behaviors to be learned if/when those genes mutate.
In humans, an enormous variety of behaviors can be transmitted very effectively and efficiently without instinct, thanks to our intelligence and ability to use language. Furthermore, we can adapt culturally much, much more rapidly than we can genetically. Humans who relied on instinct for hunting could never have learned to use spears, arrows, or shotguns until mutations produced genes for hormones and brain structures that made spear-, arrow-, or shotgun-making instinctively satifying. Given this, it’s easy to see why hominids with strong instinctive behaviors would rapidly lose out to more culture-dependant humans.