Scientific evidence of reproduction urge?

July 11, 2007 3:37 PM

Is there scientific evidence that animals have an innate/instinctual urge to reproduce? Is there scientific evidence that it is the same in humans?

Disclaimer: I'm not well educated in Biology. Or at least as much as I should be.

I've always believed there is, because it was always taught as a given, but I've never actually read any scientific studies to that effect. Is our opinion that all animals have an innate/instinctual urge to reproduce purely based on non-scientific evidence?

This question is sparked because my brother feels that animals actually only have an innate/instinctual urge to have sex and that reproduction is only a by-product, in that it's not intentional, either intellectually or innately/instinctually (and that with humans it's a bit different due to the intellectual aspect of it). I disagreed in that I always thought the urge was to reproduce and that sex was the by-product. I do agree though that I feel with humans it's a bit different due to the intellectual aspect...

I tried to google for some scientific evidence, but any mention of such urge is only in passing or editorial.

I'm fairly certain that I hold the majority viewpoint, so I don't just need people saying yes or no, this is right or that is right (although, viewpoints based on actual knowledge of the field are welcomed). What I'm wondering is if we can scientifically study that these urges exist, and if so, what have been the outcomes of such studies?

Sorry about how long-winded this is, but I just wanted to get this question out there.

posted by defenestration to science & nature (45 comments total)

My sociology professor spoke at length about how humans don't have any instincts, so here's that theory:

Instincts are things that animals do without being taught, and all of the animals of a species do it. The common example is one bird that builds a spherical nest...even if it's raised in captivity and never meets another bird, it still builds the same shape nest. There's no behavior that all humans do without fail and without being taught - from reproduction, to sheltering themselves, even survival and walking upright (as evidenced by feral children) - all are learned behaviors.

I'll see if I can dig out the studies referenced; this is a pretty common sociological theory.
posted by lhall at 3:46 PM on July 11, 2007

Interesting. Would that imply that in animals there is a reproduction instinct?
posted by defenestration at 3:49 PM on July 11, 2007

my brother feels that animals actually only have an innate/instinctual urge to have sex and that reproduction is only a by-product

Your brother's theory doesn't take into account organisms that reproduce asexually. Before animals gained the ability to reproduce sexually, they still had the instinct to reproduce.
posted by rancidchickn at 3:50 PM on July 11, 2007

Think of it in a Darwinian sense. Animals don't know that sex leads to reproduction (and probably for a large part of history, people didn't either), but animals that desire to have sex will leave more offspring than animals that don't, hence more animals will want to have sex. It's the same idea that animals that just happen to have better ability to evade predators or get food (e.g., longer legs for running, longer necks for reaching branches) will survive longer and produce more offspring (who also have longer legs or longer necks).
posted by matildaben at 3:51 PM on July 11, 2007 [1 favorite]

Mammals, birds, and certain species of reptiles and fish devote significant resources toward the care of their offspring. If there were only an instinctual urge for sex, there would be no reason to care for the newly born.
posted by jamaro at 3:51 PM on July 11, 2007 [1 favorite]

It's not an either/or question. There's an urge to mate, and later there's an urge to care for the young (unless were talking about the many animals that don't invest any care at all towards their offspring).

Some animals have sexual behavior that has nothing to do with reproduction--homosexual pairings, or the sexual free-for-all of bonobo social relations, for example.
posted by hydrophonic at 3:57 PM on July 11, 2007

Thanks for the response... keep them coming. These explanations definitely do touch upon some of what I already knew, but for some reason I was having trouble backing up my understanding.

I should read more about biological and evolutionary science. Side question... anyone have any books relating to this discussion that a layman could pick up and enjoy/learn from? Bonus points if it's not ultra-dense.
posted by defenestration at 3:58 PM on July 11, 2007

It is more of a semantic question than a factual one that can be proved/disproved by experimentation. The urge is to engage in behavior that maximizes the chance for reproduction of the animals genes. Everything else is a side effect. I highly recommend The Selfish Gene for an engaging read that lays a good foundation for understanding this.

"no behavior that all humans do without fail and without being taught"

Pulling one's hand away from contact with flame would seem to be instinctual behaviour.
posted by Manjusri at 3:58 PM on July 11, 2007

The Selfish Gene, by Richard Dawkins would give you a fairly good scientific background on which you could base your (correct) argument.
posted by emd3737 at 3:59 PM on July 11, 2007

Two things: 1) Not all reproduction is sexual. 2) Why stop at animals? Think about each of these, and whether it's having "sex" for pleasure. Chimpanzees. Rhinos. Mice. Chickens. Jellyfish. Elm trees. Yeast. Viruses. A few bits of RNA.

They all reproduce. Everything that fails to have a strong drive to reproduce doesn't make copies of itself, and when it dies, the ambivalence dies with it.

We all have a common ancestor: a teeny few bits of atoms that tended to make copies of itself from the environment. The copies were never always perfect, and some self-copying accident results were better at making self-copies than others. Most everything didn't work and died. But, the stuff that lived and made copies, lasts. 2 thousand thousand thousand years later, it led to hummingbirds outside, still making copies of themselves.

Everything that gets in the way of making copies is a hindrance to the survival of that hunk of information. The hunk of information in you, elm trees, rhinos, and viruses has a strong, strong history of giving your very good direction to reproduce.

What we call the act of sex is pleasurable and we do it because, to not do it or find it enjoyable makes us far less likely to pass on our genes. It's continually reinforced, and those who have a stronger drive will create offspring with that stronger drive.
posted by cmiller at 4:02 PM on July 11, 2007

For book recommendations, thirding The Selfish Gene, as well as The Ancestor's Tale, also by Dawkins.
posted by jamaro at 4:03 PM on July 11, 2007

Yeah, Dawkins would explain far better than I could. Fourthing "The Selfish Gene".
posted by cmiller at 4:05 PM on July 11, 2007

I was definitely already aware of non-sexual reproduction... I just forgot to include it in the question.

I'm definitely buying "The Selfish Gene" the next time I'm at a book store. Any more insights and recommendations are welcome!
posted by defenestration at 4:09 PM on July 11, 2007

Soy el hermano. ;-)

All great responses, and much to my satisfaction, it's not a cut-and-dry issue-- especially good point about the distinction between reproductive behavior and sexual behavior (specifically among Bonobos). I tend to agree that it's a semantical question as did my brother, but my main position was a naturalist one which precluded the notion of reproductive "urges" as it seems anthropomorphic. I defended this position by stating that sex was the behavior which led to reproduction, and that this behavior would be selected due to its positive gain. However, the intent to reproduce seemed, IMHO, too clairvoyant to be realistic. How does the Darwinian explanation tackle this?

It made sense to me that reproductive behaviors, like sex, were instinctual, but my position was firm that the behaviors were instinctual not the "intended" consequences.

Caring for young, etc. although not universal is a good argument towards knowledge of what was to come (e.g. building a nest, etc.), and it certainly makes the subject murky. If these animals are choosing to reproduce, then it's not strictly an instinct as we have been discussing.

More naturally, the asexual reproduction is instinctual, and a great point to make. My only concern is there is not intent towards these behaviors, and it's just a process these organism and even insects undergo.
posted by quanta and qualia at 4:12 PM on July 11, 2007

Biological Exuberance: Animal Homosexuality and Natural Diversity by Bruce Bagemihl is fascinating and quite readable by the non-expert.

"Courtship, sex, affection, gathering food, finding a home--they have all been observed among a range of partners, from heterosexual to homosexual to somewhere in between," Bagemihl says. "And there are some animals who don't have sex at all." Although he doesn't claim to know the motivations of animals, Bagemihl says he does know procreation is not always the driving force: "Same-sex couplings occur in the presence of the opposite sex, in and out of captivity, and in and out of mating season."
posted by Carol Anne at 4:21 PM on July 11, 2007

Pulling one's hand away from contact with flame would seem to be instinctual behaviour.

The sudden jerk your hand does when you get it into a flame without realizing it is a spinal reflex, not a "behavior" as that word is usually defined. That reflex can be overcome with attentive effort; some people can hold their hands in flame until all the skin crisps away. (In fact, this ability was used in Frank Herbert's Dune as a test to segregate humans from animals, as it is a fundamentally human ability.)

Understanding the inner life of animals - how they make their decisions, what they are thinking or feeling from time to time - is not a scientific pursuit; it is a philosophical one. The same is true of humans, in fact, and it will continue to be true unless reliable mind-reading technology is developed.
posted by ikkyu2 at 4:26 PM on July 11, 2007

+1 manjusri. If you have urges to engage in behaviors that maximize your reproductive chances, is that different from having an urge to reproduce? Especially if you're an animal with no theory of mind? Seems like a semantic distinction.

Taking care of the young is just one of the ways that sexually reproducing animals maximize their chances. There are all kinds of elaborate, subtle, or surprising ways that animals do this.

One recent news item discussed females in pair-bonding species that will cuckold their males, to get it on with a more genetically desirable male.

In baboon societies, you get dominant males with harems of females as one type of social group, and "bachelor tribes" as the other. When a bachelor tribe happens upon a harem, first the bachelors kill the dominant male. Then the bachelors all duke it out with each other, until only one is left. Then they kill any young offspring, which sends the females into estrus.

Dragonfly males have "spades" on their penises that they use to dig out any sperm left behind by other males when they impregnate females.

And so on.
posted by adamrice at 4:27 PM on July 11, 2007

Humas have all kinds of instinctual behaviour: interest in and generally caring to babies, fear of various large animals, not looking at the sun etc.
posted by fshgrl at 4:42 PM on July 11, 2007

Do some reading on the phenomena of estrus. Estrus is when a female of a species comes into season and becomes interested in mating. Sexual activity outside of estrus is not going to lead to reproduction.

In many species, sexual activity rarely happens outside of estrus. Males tend to live with males (or alone) and females tend to live with females and offspring. There may be one or two males as part of a herd, but they are generally there for the purposes of organization, defense, and protecting the right to mate when females are in season.

The females really don't want to have anything to do with the males in many species when they are not in estrus. That's actually one of the reasons that Pandas are so endangered. They are too cross to fuck. When its not breeding season, they can't stand to be around each other and wander far afield. The period of estrus is pretty narrow in that species, so they have a hard time finding mates when the season is actually right.

Humans (and a handful of other creatures) are novel in respect to estrus. We have what is known as hidden ovulation. It can be difficult to tell when a woman is ovulating and therefore ready to breed. This has a number of ramifications for our social structure and male/female interactions and those consequences are a matter of some debate.

So I would say that all animals have a reproduction instinct. Some animals also seem to have a sex drive that is not intrinsically related to breeding. I think that's a really neat thing about humans, but should not be abstracted to other animals.
posted by afflatus at 4:46 PM on July 11, 2007

The Selfish Gene, by Richard Dawkins would give you a fairly good scientific background on why your argument is incorrect.

Functionally: The instinct/urge is for sex and other behaviours like care of offspring etc., with reproduction as a by-product. Animals (including humans, regardless of what many sociologists think) have instincts which cause behaviours which cause reproduction, so the instincts cause reproduction indirectly. It doesn't make sense that a mouse has sex because it desires the presence of baby mice a few weeks down the line, for that to work the mouse would have to actualy understand the link between sex and birth, and I don't think mice know that, or reason that far ahead. Animals are born with instincts which cause wants and behaviors, not knowledge.

Teleologicaly: Those instincts are only there because they cause successful reproduction. The desire for sex (along with caring for offspring etc.) is an outcome of natural selection (for successful reproduction), so reproduction is the ultimate "reason" for the urge for sex, and indeed every other instinct.

In the life of one animal, sex causes reproduction. Over evolutionary timescales, reproduction causes sex.
posted by Canard de Vasco at 4:49 PM on July 11, 2007

There's no behavior that all humans do without fail and without being taught - from reproduction, to sheltering themselves, even survival and walking upright (as evidenced by feral children) - all are learned behaviors.

This theory is massively amplifying the significance of human exceptions, I think.

For example, lots of people argue that animals are less sensitive to low level environmental radiation than humans. However, the effect of such radiation on humans is actually very subtle, a slight increase in the leukemia rate here, a slight increase in breast cancer there.. It is easy to detect statistically unlikely things in human populations, but very hard to detect the same in animals.
posted by Chuckles at 5:02 PM on July 11, 2007

Humans have plenty of instincts: crying, sucking, fear of large animals, pack behavior, and so on. The urge to have sex is also present in essentially all humans. I would certainly agree with your brother that the urge is to have sex, not to "reproduce", as no animals know that sex leads to reproduction and even in human history this knowledge is rather recent.
posted by jellicle at 5:07 PM on July 11, 2007

The central tenet of evolution:

That which reproduces most effectively in the previous generation is more prevalent in future generations.

Do you think that organisms that lack a desire to reproduce will last for very many generations in the presence of competing organisms having such an instinct?

Non-human animals (and seemingly, many humans as well) don't understand that sex -----> reproduction, hence the desire to have sex is what drives reproduction in animal populations.

Exercise: Consider the question for plants as well.
posted by mharper3 at 5:30 PM on July 11, 2007

I'd like to offer the ostrich as a case study.

In the wild, a male ostrich mates with as many females as he can. He also builds a nest. When his mates are ready to lay eggs, they show up and use his nest, leaving fertilized eggs behind which are (usually) his offspring. Once they've laid their eggs, he chases them away. (Until they show up ready to lay again.)

Eventually he ends up with quite a nest full of eggs, (nearly) all of which are his children. He then sits on them until they hatch, and cares for the chicks until they're old enough to have a decent chance of surviving on their own. And if anything or anyone tries to get near his chicks while he's caring for them -- including the females who contributed eggs to his clutch -- he will chase them away violently.

Which can be pretty violent. A full grown ostrich can easily kill a human with a disembowling kick.

It's obvious that the male ostrich is doing a lot more than just looking for opportunities to have sex with female ostriches.

Another example: the Nile crocodile. A female Nile crocodile climbs up on a river bank, dig a hole, lays her eggs, and buries them. Then she guards the nest until the eggs hatch. Afterwards, the young crocodiles stay near her for protection until they're pretty good sized.

When danger approaches, they hide in her mouth. (Early observation of this completely misunderstood it and assumed that the female crocodile was engaging in cannibalism because she was too stupid to know better. Later research has corrected that misapprehension.)

She doesn't eat while any of this is going on, a period of several months.
posted by Steven C. Den Beste at 5:42 PM on July 11, 2007

The central tenet of evolution: That which reproduces most effectively in the previous generation is more prevalent in future generations.

If there is a central tenet of evolution, that's not it. That might be a good tenet of natural selection though.

How can you study your question scientifically? I think the question is ill-formed. You would need to define how you would know that something is reacting to an urge to reproduce rather than an urge to have sex. And if you want to have a meaningful discussion with your brother on the subject, you'll have to agree on the definitions.

Until you do that, you can't really get a good answer here.
posted by grouse at 6:00 PM on July 11, 2007

"The sudden jerk your hand does when you get it into a flame without realizing it is a spinal reflex, not a "behavior" as that word is usually defined."

Webster's defines behavior as "b: anything that an organism does involving action and response to stimulation." Are you using more of a technical/jargon definition that excludes reflexes?

I'm also a bit puzzled by the original assertion that instincts cannot be overridden. Websters defines instinct as: " a largely inheritable and unalterable tendency", which is a bit vague but implies that there are exceptions.
posted by Manjusri at 6:30 PM on July 11, 2007

My understanding is that humans are born with far less pre-programmed (instinctual) behavior than most other species, but that they certainly do have instincts. Anyone who has ever been around an infant knows that they do not need to be taught to cry when they're hungry or to suckle. There is at least enough instinctual behavior in humans to help them survive infancy.

The instinct to care for infants is probably unrelated to sex, as I see it. Of course, it's likely that it has also been selected for, because the descendants of animals that care for their young are more likely to survive to adulthood than the descendants of animals that don't. But it does seem logical that there was no real way for early humans, or any animal for that matter, to truly understand the connection between sex (especially if they have a lot of it with a lot of partners) and birth (some lengthy period of time afterward).

This book review relates some interesting points on caring for infants, including the idea that at some times, infanticide is the wiser evolutionary choice,
posted by Miko at 7:17 PM on July 11, 2007

My sociology professor spoke at length about how humans don't have any instincts ... There's no behavior that all humans do without fail and without being taught

Your professor is utterly, totally full of shit.

The list of biologically driven behaviors on display by humans is nearly endless. Starting with infants, you have APGAR grimace tests, suckling reflexes, Moro reflexes, the Palmar grasp, Plantar grasp, rooting reflexes, stepping reflexes, tonic neck reflexes, swimming reflexes, etc, etc. These are all things humans do without being taught.
posted by Cool Papa Bell at 8:42 PM on July 11, 2007

Hormones drive the sex when females are "in heat" to use plain terms. However, some mating rituals are taught from generation to generation or females will use selective factors to secure the best mate and thus the best offspring (that's where evolution and natural selection come into play--if you have a gene that's giving you a better chance of mating, then it's more likely to be passed on). For example, peacock's feathers: the bigger and brighter a male's feathers, the more interested the female is; same way for deer when they fight, they fight over females and they know females are in heat by the pheromones and hormones produced.
posted by uncballzer at 8:55 PM on July 11, 2007

Anyone who has ever been around an infant knows that they do not need to be taught to cry when they're hungry or to suckle.

As a three month premie baby, I was born not knowing how to suckle. While 'taught' is probably not entirely accurate given the likely impossibility of teaching anything at that age, it seems at least somewhat true to say that I needed to be taught to suckle.

That said, and so I actually contribute to the thread in this post, it seems to me that 'reproduction' is a bit high level, and what we can observe is an instinct towards activities leading to and associated with reproduction.

As for the issue of asexual reproduction, is there actually anything that reproduces asexually which is complex enough to possess the abstraction of 'instinct'? I can't think of anything, so it seems like a bit of a false issue on this topic. Likewise, plants don't have an instinct towards reproduction because I don't see where they can be meaningfully said to have an instinct towards anything.

Maybe we need to come to an agreed upon definition of what an instinct is here, because it doesn't seem immediately obvious that everyone here is in agreement on this.
posted by Arturus at 8:57 PM on July 11, 2007

Oh, meant to include with the teaching of rituals: some birds will do special dances in front of their potential mates. They will learn these dances from their parents, etc. If performed correctly, a female/male will choose to mate with that bird. If performed incorrectly, he ain't gettin lucky tonight . . .
posted by uncballzer at 9:00 PM on July 11, 2007

"My sociology professor spoke at length about how humans don't have any instincts"

This is apparently a common assertion in introductory sociology texts, but it sounds highly dubious, and perhaps based on differences in use (or misuse) of terminology as Arturus noted.
posted by Manjusri at 10:39 PM on July 11, 2007

The "nature versus nurture" argument is an old one in social science circles, but for many involved it's become politically incorrect to contend that anything is "nature". To even suggest such a thing will land you in hot water. You wouldn't believe the names you'll get called. Just ask Lawrence Summers.

That sociology professor who claimed that humans don't have any instincts was toeing the party line. It would be interesting to know what he'd say about that subject in private, to people he trusts.

It's sad. That's not how science is supposed to be done. This kind of abuse of the process is one of the reasons why the social sciences have fallen into such disrepute in the last twenty or thirty years.
posted by Steven C. Den Beste at 11:34 PM on July 11, 2007

While 'taught' is probably not entirely accurate given the likely impossibility of teaching anything at that age, it seems at least somewhat true to say that I needed to be taught to suckle.

No, it's not really true at all. It's just not at all a valid description of what occurred in your example. As a preemie, you lacked the neurological development at that stage for the reflex to be present in a significant fashion. Given a few more weeks in utero, you'd have been fully cooked, so to speak. Instead, the rehabilitative process included treatments where you were prompted to suckle, and given opportunity to suckle something that provided additional neurological stimulus (i.e. feeling something in your mouth, feeling/tasting nutritional stimulus, etc), in order to hopefully speed along the final neurological development that results in the healthy reflex.

Calling this rehab "teaching and learning" is a misuse of terms that leads to greater misunderstanding. If you lift weights, you are not "teaching" your muscles to grow bigger. If you are frightened by a scary movie, your heart does not "learn" to beat faster.

When sociologists get off the ranch and start ignoring the biology involved, and spread their wrongheaded ideas around, that's when you get an AskMe question with a lot of wrong answers. ;-)
posted by Cool Papa Bell at 11:41 PM on July 11, 2007

Understanding the inner life of animals - how they make their decisions, what they are thinking or feeling from time to time - is not a scientific pursuit; it is a philosophical one. The same is true of humans, in fact, and it will continue to be true unless reliable mind-reading technology is developed.

Such a technology may already exist, at least to a limited extent.
posted by flabdablet at 6:07 AM on July 12, 2007

You wouldn't believe the names you'll get called. Just ask Lawrence Summers.

Sorry for the derail, but Lawrence Summers wasn't in the position of making a scientific point when he proposed that males and females might have different abilities in math and science. He was the president of Harvard which is an administrative position and I assume he had a large influence on who was hired or fired at the University. For a person in such a position to make the proposition he made is completely irresponsible and female scientists had every right to doubt that he would treat them fairly.
posted by afu at 6:15 AM on July 12, 2007 [1 favorite]

I agree that this discussion and what happened to Lawrence Summers are two vastly different things; but not least because there is a difference in saying some few behaviors are instinctual at birth, and that abilities such as skill at math are instinctual at birth. Most scientists are agreed, as noted above, that some behaviors appear spontaneously in humans, but very few, in comparison with other species. Humans have much more learned behavior than instinctual behavior. Suggesting that skill at math is biologically pre-determined by gender shows a reductive understanding of nature and nurture that is embarrasingly reductive and unscientific; Summers' misunderstandings set him up to be a very poor administrator. But it isn't an entirely black-and-white phenomenon (it's all instinctual! It's all learned!) Most human behavior is learned, but nature and nurture interact in complex ways which are not yet well understood.

Cool Papa Bell is right about the preemie argument, as well. In a state of nature, a baby born without the ability to suckle would not be likely to survive. Premature infants are able to survive to the degree that they are in today's world only because centuries of observation, reliable data, experiment, and standard medical practices have created protocols for treating babies like this that enable them to overcome the lack of development at premature birth, which once was almost always a death sentence. Babies who had completely developed in the womb and had the suckling instinct firmly in place would be more likely to survive and thus reproduce. Most babies don't have to be taught - the ones who are able to learn despite developmental delays or early birth are benefitting from the helps of modern medical science which can in some cases counteract a life-threatening biological disadvantage.
posted by Miko at 6:37 AM on July 12, 2007

"My sociology professor spoke at length about how humans don't have any instincts"

This is apparently a common assertion in introductory sociology texts, but it sounds highly dubious, and perhaps based on differences in use (or misuse) of terminology as Arturus noted.

As ikkuy2 pointed out, instinct is generally distinguished from a reflex. An example of instinct would be the elaborate mating rituals of many birds. If you raise a male bird from the time it is hatched and never allow it to see another bird of its species and then expose it to a female at the appropriate age, it will perform a mating dance that is indistinguishable from birds that have grown up around their own kind.

The complexity and variety of instincts lessens with the animal's ability to learn, so mammals in general have fewer instincts that birds or reptiles. A monkey raised in captivity will not know the mating signals of wild monkey, and indeed may never develop any effective mating behaviour at all---my primates prof showed us a picture once of a juvenile male monkey raised in captivity masturbating next to an adult female who was presenting (the monkey signal for 'take me now'). This lack of knowledge about how to mate has been widely observed in monkeys raised in isolation or near isolation. Similarly, apes have little success raising their own first babies in zoos, such that the babies are often either removed for the first few weeks and then returned, or removed and given to an ape who has had experience raising babies (who may then be moved to the same enclosure as the bio-mother so that she can learn parenting skills).

Apes also have enough intelligence to be aware those instincts that they do have. A chimp in captivity was once observed to come across some food that was not enough to share. It began to call out--an instinct for chimps--but clamped its hand over its mouth so as to muffle the sound and eat the food itself. It seems reasonable to suggest that as intelligence increasing allows for overriding and changing instinctual behaviour, instincts will become less selected for.

By the time you get to the intelligence of humans, there do not seem to be any encoded behaviours. Saying that humans do not have instincts IS NOT THE SAME as saying that their biology does not affect their behaviour. If humans had instincts in the way the word is normally applied to animal behaviour, we'd find universals that are far more specific than the list Pinker uses. We'd find really specific things that didn't vary a lot between societies or languages. So, if absolutely everyone in the world, regardless of the language they learned, called out the equivalent of "Hey, look at this!" every time they found a bush with berries on it, that would be an instinct. If all dates followed the same format, that would be an instinct. On the other hand, finding that every society develops music certainly implies something about a biological influence, but a proclivity for music at the level of society is not the same as an instinct. It would be instinct if every person was born knowing the same song.

So, SCDB, it is not actually toeing any "party line" to say that humans don't have instincts. It is using the term in the biological rather than the colloquial sense. Larry Summers didn't say that human's have instincts. He said their were innate differences in genders. Whether that is right or wrong is irrelevant to the question of whether humans have instincts.

Whether desires are instinctual is much harder to determine. You have to use indirect measures, which is tricky. I would separate out a few factors to look at a desire to reproduce: there is the desire to have sex, the desire to have one's own biological children, and the desire to raise children.

In humans, the desire to have sex acts independently of the desire to have or raise children, as evidenced by the number of people who do not want to have or raise children at the time that they are having sex. I don't think we need to look for an instinct to have sex, since there is abundant evidence that animals will engage in pleasurable pursuits when the opportunity arises, and sex for humans is (once you learn how to do it right) generally a pleasurable experience.

The desire to have one's own biological children is a bit more difficult to sort out. On the side of innate desire, there are the people who go to extraordinary lengths to have a child that is biologically linked to them, rather than adopting, or adopting as a final measure only. On the side of not innate, there are/have been many societies where certain social conventions and/or rituals are considered the primary source of relationship, and biology is secondary or unimportant. Further, in the societies where people go to great lengths to have biological children, biological relationships are often considered more 'real' than other relationships, thus complicating whether the desire to have one's own children derives from something innate or a cultural value.

People from every living society seem to have the desire to raise children. Again, it is difficult to determine the role of cultural values in this. In industrial societies we have seen the number of by-choice childless couples increase, but that again could come from cultural values rather than a (lack of) innate desire. Anthropologists have done studies that show people reshaping their desires according to certain principles, which suggests that many desires which might be termed 'innate' in humans are also fairly plastic.

My own feelings, which are based on education in human and primate evolution and human social diversity, but which are not based on some specific study, are that the desire to *raise* children has biological influences, but not in as strict a way as an instinct. The desire to have sex is certainly linked to biology, through the physicality of pleasure. However, I suspect that the 'desire to reproduce' in the specific sense that 'reproduce' implies is a cultural desire formed at the intersection of valuing biological relationships and learning about evolution.
posted by carmen at 7:25 AM on July 12, 2007 [1 favorite]

As ikkuy2 pointed out, instinct is generally distinguished from a reflex.

Okay..

An example of instinct would be the elaborate mating rituals of many birds.

So, instinct implies a fairly complex action, over time.

The complexity and variety of instincts lessens with the animal's ability to learn,

That is a really interesting observation, but.. Well, we need a concise definition of instinct then - draw a line.

it began to call out--an instinct for chimps--but clamped its hand over its mouth so as to muffle the sound and eat the food itself.

Well, comparing the bird to ikkyu2's reflex example.. I have to think the chimps action sounds a lot more like reflex than complex behaviour to me..

I certainly can appreciate that the bird's nest, or spider's web, are entirely more complex than any "instinctual" behaviours humans exhibit. But, reflex doesn't seem to cover enough territory to capture unconscious human flirting displays. Women wear less clothing closer to ovulation, men tend to be more competitive as soon as a woman is around to impress, and so on..

Could it be that the definition of instinct is teleological? Humans do not have instincts, all other animals have instincts, and to maintain this truth as we learn more, the definition is changed. Is there another word for actions which are between instinct and reflex (maybe I just missed it up thread)?
posted by Chuckles at 9:53 AM on July 12, 2007

Women wear less clothing closer to ovulation, men tend to be more competitive as soon as a woman is around to impress, and so on..

These examples do not hold up cross-culturally. While there may be greater or less degrees of interaction between biology, desire, and behaviour going on in these types of examples, it is not particularly meaningful to describe them as either "reflex" or "instinct".

Is there another word for actions which are between instinct and reflex (maybe I just missed it up thread)?

From Primate Paradigms:

One of the ideas fallen by the wayside in the search for a more sophisticated understanding of behavior is the concept of instinct.... The term, instinct, usually referred to a biologically determined drive to perform a specific behavior or specific type of behavior. it was used a great deal in early ethology and psychology to explain what occurs inside the behaving animal....

This idea has become outmoded by a more thorough understanding of physiology and a more sophisticated approach to behavior. There is no evidence for action-specific energies driving and determining particular behaviors....

The word "instinct" has been largely replaced by the term "innate behavior," but this is not merely a matter of vocabulary change. Innate refers only to inherited potential or biological possibilities. This involves an important shift in emphasis from biologcial determinism to biologcial poltential because innate is a relative not an absolute term, and indicates the degree of variability we can expect in a given behavior pattern in different environments. (pgs 29-30)

So, I guess that I was wrong in distinguishing a "biological" from "colloquial" use for instinct: it seems that the only modern uses are colloquial.
posted by carmen at 10:55 AM on July 12, 2007

"As ikkuy2 pointed out, instinct is generally distinguished from a reflex."

Ikkyu2 was asserting a division between behavior and reflex in general usage. However, it appears that reflex is a subset of behavior, and of instinct in colloquial usage.

The technical/jargon usage of instinct seems somewhat muddled, with attempts to shape the definition to reach the conclusion that humans are free from instincts. This article relates some of the history of its usage, and contains the spot-on quote: "In both popular and scientific literature the term instinct has been given such a variety of meanings that it is not possible to frame for it an adequate definition which would meet with general acceptance."

Perhaps the term "innate behavior" is at least partially intended to clarify this. If so, then it is a questionable choice of words as the issue still appears muddled. A quick google didn't turn up much information, but of the three links I found: one asserts that reflexes are a subset of innate behavior. Wikipedia is ambiguous and a thin entry besides, and this definition appears to exclude reflexes.
posted by Manjusri at 12:01 PM on July 12, 2007 [1 favorite]

I may have been wrong in my assertion, actually. I am so steeped in neurology that it's not always clear to me what "general usage" is.

When I think of "behavior" I think of the things that simply don't happen anymore after bilateral frontal lobectomy, as distinct from the lower reflexes (withdraw from pain, patellar tap) which are preserved.
posted by ikkyu2 at 2:47 PM on July 12, 2007

My sociology professor spoke at length about how humans don't have any instincts, so here's that theory:

That's absurd. For one thing, even a single example disproves it. Sneezing, hickups, and sleep, blinking as things are coming close are all instinctual for example. Man, why would a sociology professor know about that anyway?
posted by delmoi at 7:18 PM on July 21, 2007

Could it be that the definition of instinct is teleological? Humans do not have instincts, all other animals have instincts, and to maintain this truth as we learn more, the definition is changed. Is there another word for actions which are between instinct and reflex (maybe I just missed it up thread)?

That seems to be be the problem. After all, "instinct" "reflex" and "behavior" are all general terms thought up by people, not hard and fast rules like you might find in physics. No one would ever confuse gravity with electromotive force, for example.

So the question of where to draw the line can be more complicated. If it's an "instinct" for a chimp to call out when it sees food, how is that different then a person calling out during orgasm, or in pain?
posted by delmoi at 7:33 PM on July 21, 2007

Thanks to everyone who helped clarify (or muddy, I guess, but what can you do) the definitions. Great comments!
posted by Chuckles at 6:36 PM on July 28, 2007