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View Full Version : How do wild animals avoid incest and inbreeding?


astro
09-15-2005, 01:02 AM
Just curious. Humans have complex social arrangements and to prevent this. How do animals manage to avoid incest and inbreeding?

As a second question, beyond animals in general, specifically how do the great apes prevent this?

FlyingRamenMonster
09-15-2005, 01:09 AM
Generally, animals that live in groups prevent inbreeding by kicking out the young males once they reach breeding age.

Simple and effective. A bit harsh, but hey.

CynicalGabe
09-15-2005, 01:43 AM
Generally, animals that live in groups prevent inbreeding by kicking out the young males once they reach breeding age.

Simple and effective. A bit harsh, but hey.

Why do you think kids get sent off to college?

lorinada
09-15-2005, 02:23 AM
A lot of them don't. In fact, it would be my WAG that most of them don't. I know the fish in my fish tank don't care, and cats don't care. I hear dogs are the same way.

HPL
09-15-2005, 02:42 AM
My mother used to live in an apartment complex with her cats, who went outside. One of them was a female, whose father was the big tomcat on the block.

Well, apparently the big tomcat gets to have his way with all the females, because he impregnated my mom's cat, several times. One cat turned out to be extremely anti-social, if not mentally damaged, but lived with her anyway. Another litter had all the kittens eventually die, mostly due to the imbreeding. I wasn't there to see it, but I was told that one kitten couldn't move it's back legs at all for weeks before it died.

So it implies that cats don't care at all. But since the inbred ones end up dying pretty quickly anyway, it doesn't really matter. Kind of like I've heard that the Ancient Egyption royalty used to marry brother to sister. Any kids who were obviously defective got a retroactive abortion.

Rhubarb
09-15-2005, 02:50 AM
Having been raised on a dairy, I can tell you there are a lot of bulls out there having mad bovine sex with their daughters and grand-daughters. Although in these days of AI (artificial insemination), chances are good that the bull and most of his offspring have never met.

Smeghead
09-15-2005, 03:39 AM
Obviously, the answer is going to vary widely between species, ranging from complex social arrangements to a simple "they don't".

WonJohnSoup
09-15-2005, 03:48 AM
Heh, one of the few things I remember from high school bio: cheetahs are so inbred that they're almost all identical.

http://lynx.uio.no/jon/lynx/cheetahg.htm

Some other links were talking about how it probably came about because of two big population crisis'.

Blake
09-15-2005, 05:23 AM
Generally, animals that live in groups prevent inbreeding by kicking out the young males once they reach breeding age.

I'm not at all certain that this is generally true. Amongst the great apes for example the norm is for the young females to be 'kicked out' and go an live with the family of unrelated males, and the human branch of the great ape family is generally no exception to that rule.

In addition to that type of arrangement we have the situation where the males and females live essentially separate lives and only come together briefly for mating as is the case for elephants, and the situations where the individuals of both sexes are essentially solitary by nature as is the case for most cats. Then of course there are numerous cases such as found amonst wolves where neither male nor female young are more likekly to be expelled.

In short I'd have to see some sort of evidence before I'd accept that animals generally expel the young males. Intuitively I'd say they generally don't.

Having said that I suspect that the general principle is sound. Most animals have some form of dispersal mechanism that more or less gurantess that inbreeding won't continue for generations. The consequences of inbreeding are not as dire as people generally assume and usually only become seriously problematic after continuous line breeding for several generations. So long as some sort of dispersal occurs to bring in fresh blood periodically it's not really a problam.

So a gorilla may well mate with his own duagther, but he will also inevitably mate with unrelated females from neighbouring tribes. That ensures that fresh blood is constantly being added to the tribe and through pure chance within a few generations the dominant male will be one of his progeny from an unrelated female and hence inbreeding will have ended. In fact such a process will be accelerated as soon as inbreeding produces any detrimental effects since only males not suffering from the defects will rise to dominance. As a reuslt inbreeding will be at worst a nusiance.

The same priniciple applies to cats, where a tom will only win out in fights for mating rights with his own daughters/granddaughers for a few generations before an unrelated rival wins his territory and so on for the various other arrangements.

IOW so long as some animals are moving away form their own family members and so long as competetion for mates exists there is automatically a mechanism to prevent inbreeding.

BTW, there is more involved in human avoidance of inbreeding than social customs. People put great selective value on mates that are not deemed to be close relatives and the selection seems to have little to do with culture or even conscious choice. It's entirely possible that similar instincts exist in other animals.

micco
09-15-2005, 09:08 AM
The Ngorongoro lions (http://ntz.info/gen/n00443.html) are an example of a group that is significantly inbred because of their small numbers and isolation from other groups.

Annie-Xmas
09-15-2005, 09:22 AM
Woman is afraid her female cat has a tumor, so she has the vet make a house call. Vet informs her the cat is simply pregnant.

Woman: That's impossible. She never goes out.
Vet: Isn't that a male cat on that chair?
Woman: But that's her brother!

rainy
09-15-2005, 11:52 AM
I can't find a cite now, but I've always heard that straight line breeding (fathers impregnating daughters) doesn't produce the defects that brother sister crosses do. So with dominate males getting most of the 'rights' and with short lifespans of lots of wild animals, it (the bad interbreeding) may just not actual happen very much.

-rainy

Colibri
09-15-2005, 12:29 PM
A lot of them don't. In fact, it would be my WAG that most of them don't. I know the fish in my fish tank don't care, and cats don't care. I hear dogs are the same way.

You can't base anything on the behavior of domestic animals, or animals in captivity. If animals don't have a choice, or don't have much of one, most will mate with offspring or siblings.

Research has demonstrated that some animals, in particular some rodents, are able to recognize kin (apparently through olfactory signals) and avoid breeding with them. One example is here (http://wits.ac.za/apes/Pillay/Pillay2002.pdf ). (Warning: pdf) Many others can be found by googling "inbreeding avoidance mate choice."

As has been said, in many animals, whether social or solitary, one sex or the other typically disperses from the social group or the territory in which they were born. This is probably the most common mechanism for incest/inbreeding avoidance. However, other mechanisms exist for kin recognition and the avoidance of inbreeding.

Teter
09-15-2005, 12:34 PM
You can't base anything on the behavior of domestic animals, or animals in captivity. If animals don't have a choice, or don't have much of one, most will mate with offspring or siblings.

Amish???

RandomLetters
09-15-2005, 01:37 PM
Amish???
A better example might be middle eastern cultures, which have high levels of cousing marrying - in Saudi Arabia, for example, 41% of people (http://ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9230979&dopt=Abstract) are married to their second cousin or closer relative.

astro
09-10-2010, 04:54 AM
You can't base anything on the behavior of domestic animals, or animals in captivity. If animals don't have a choice, or don't have much of one, most will mate with offspring or siblings.

Amish???

It may not be incestual inbreeding, but limited mate selection and a small population leads to a raft of genetic diseases (http://cbsnews.com/stories/2005/06/08/60II/main700519.shtml) that affect the Amish.

Der Trihs
09-10-2010, 06:38 AM
Research has demonstrated that some animals, in particular some rodents, are able to recognize kin (apparently through olfactory signals) and avoid breeding with them. One example is here (http://wits.ac.za/apes/Pillay/Pillay2002.pdf ). (Warning: pdf) Many others can be found by googling "inbreeding avoidance mate choice."Another possible example would in fact be humans; women can according to some studies detect how similar the major histocompatibility complex (http://en.wikipedia.org/wiki/Major_histocompatibility_complex) of a man is to that of her father by scent, and tend to find (http://en.wikipedia.org/wiki/Major_histocompatibility_complex#MHC_and_sexual_selection) the scent of males with highly similar MHCs a turn off.

Leaffan
09-10-2010, 08:32 AM
My mother used to live in an apartment complex with her cats, who went outside. One of them was a female, whose father was the big tomcat on the block.

Well, apparently the big tomcat gets to have his way with all the females, because he impregnated my mom's cat, several times. One cat turned out to be extremely anti-social, if not mentally damaged, but lived with her anyway. Another litter had all the kittens eventually die, mostly due to the imbreeding. I wasn't there to see it, but I was told that one kitten couldn't move it's back legs at all for weeks before it died.

So it implies that cats don't care at all. But since the inbred ones end up dying pretty quickly anyway, it doesn't really matter. Kind of like I've heard that the Ancient Egyption royalty used to marry brother to sister. Any kids who were obviously defective got a retroactive abortion.

I can't agree with any of this.

Surely inbreeding is something that limits the gene pool over many successive generations, and doesn't at all mean that an entire litter will die because of "inbreeding." Limiting the gene pool potentially makes offspring more susceptible to disease, or malformations, if a gene or set of genes is missing. It's not an instant killer.

Sailboat
09-10-2010, 08:39 AM
and with short lifespans of lots of wild animals

What would this have to do with it? Either the animal lives long enough to propagate or doesn't; once the animal has propagated, dying won't undo the genetic legacy.

md2000
09-10-2010, 09:09 AM
I remember reading once about the cultural result of kibbutz life in Israel; some psychologist observed that guys were less interested in the girls they were raised with than with strangers. Unrelated children are raised in an almost communal lifestyle as close as brothers and sisters - and the theory was that there's an instinctive desire for strangers instead. (Of course, like any human urge, the rule is never 100%).

For solitary wandering animals, the general pattern of dispersal probably helps prevent long-term inbreeding. For harem-pattern breeding and expelled males, the requirement that the dominant male come from the outside (old enough) and defeat the current dominant male helps ensure that the male is healthy and that there is a decent chance it is a stranger to the herd. I guess it depends how far the solitary males wander.

For giant flocks, schools, whatever - sheer population size and random pairing would ensure that the odds are low that any incest would be more than a single occurence.

Tom Tildrum
09-10-2010, 10:16 AM
Given that my (female) dog will occasionally hump my leg, I don't think animals have very complex notions of how sex works or when it might be a bad idea.

Annie-Xmas
09-10-2010, 10:39 AM
Do zombie animals hump their own relatives?

Ike Witt
09-10-2010, 12:01 PM
Surely inbreeding is something that limits the gene pool over many successive generations, and doesn't at all mean that an entire litter will die because of "inbreeding." Limiting the gene pool potentially makes offspring more susceptible to disease, or malformations, if a gene or set of genes is missing. It's not an instant killer.

Doesn't inbreeding sometimes happen when a population becomes isolated, and sometimes lead to speciation?

flano1
09-10-2010, 03:29 PM
http://lynx.uio.no/jon/lynx/cheetahg.htm[/url]

Some other links were talking about how it probably came about because of two big population crisis'.


Lynx links! Love it.

Arrogance Ex Machina
09-10-2010, 04:49 PM
I remember reading once about the cultural result of kibbutz life in Israel; some psychologist observed that guys were less interested in the girls they were raised with than with strangers. Unrelated children are raised in an almost communal lifestyle as close as brothers and sisters - and the theory was that there's an instinctive desire for strangers instead. (Of course, like any human urge, the rule is never 100%).

The obligatory Wikipedia link. (http://en.wikipedia.org/wiki/Westermarck_effect#Westermarck_effect)

It seems we don't really need those complex social mores that much - as long as the siblings are raised together, nature will take care of things. Of course if that's not the case, well ... another obligatory Wikipedia link. (http://en.wikipedia.org/wiki/Genetic_attraction)

Chefguy
09-10-2010, 06:36 PM
The Ngorongoro lions (http://ntz.info/gen/n00443.html) are an example of a group that is significantly inbred because of their small numbers and isolation from other groups.

African Wild Dogs are endangered. One of the theorized causes is that they are all descendents of a small surviving and incestuous pocket from an ice age era. They are very susceptible to disease.

09-10-2010, 08:13 PM
I can't find a cite now, but I've always heard that straight line breeding (fathers impregnating daughters) doesn't produce the defects that brother sister crosses do.In horses, that is referred to as linebreeding for father-daughter or mother-son crosses, vs. inbreeding for brother-sister crosses. Many hoirse breeders claimed that linebreeding was OK, but not inbreeding.

But from what I know of genetics, I don't see that there is any difference between them.

BigT
09-11-2010, 01:40 AM
Another possible example would in fact be humans; women can according to some studies detect how similar the major histocompatibility complex (http://en.wikipedia.org/wiki/Major_histocompatibility_complex) of a man is to that of her father by scent, and tend to find (http://en.wikipedia.org/wiki/Major_histocompatibility_complex#MHC_and_sexual_selection) the scent of males with highly similar MHCs a turn off.

I was going to mention that. But you left out the most interesting part. Similar studies show that, when it comes to visual cues, both women and men tend to pick people who look more similar. It seems we have two competing urges.

I have no idea if this applies to other animals.

naita
09-11-2010, 03:57 AM
Just curious. Humans have complex social arrangements and to prevent this. How do animals manage to avoid incest and inbreeding?

As a second question, beyond animals in general, specifically how do the great apes prevent this?

Through chance.

kimera
09-12-2010, 03:33 PM
As Blake mentioned, most great apes have a female dispersal system, although, in practice, both sexes disperse. Most intelligent primates recognize kin and avoid mating with them, although how they do this, we don't know. Among the capuchins I studied, males disperse, but sometimes the alpha male will remain in a group after his daughters grow. His daughters never solicit him for sex and he shows no sexual interest in them.

Shekinah
01-10-2011, 11:44 PM
Hey! Here's a suggestion--perhaps animals who tend to be predatory kick out the females, whereas animals who tend to be prey kick out the males when they come of age. Horse herds for example kick out the males, whereas great apes as has already been stated tends to kick out the females. My guess is that a group of young female prey animals would have a far smaller chance of survival in the wild than a group of young males would; on the other hand, males of more predatory groups tend to rule the roost over females in a way which does not happen nearly as often among prey animals [if at all, fuzzy on the details I just remember my generalities from my "Kratt's Creatures" phase]. Thus the males of predatory groups would be less likely to leave, especially because a young group of female lionesses, for example, would have a much easier time of it trying to survive than a group of young does or impalas or even zebras would.
Just a suggestion--but a sound one, don't you think?

RadicalPi
01-11-2011, 01:40 AM
It may not be incestual inbreeding, but limited mate selection and a small population leads to a raft of genetic diseases (http://cbsnews.com/stories/2005/06/08/60II/main700519.shtml) that affect the Amish.

To say nothing of the Hapsburgs:

From http://en.wikipedia.org/wiki/Inbreeding

The most famous example of a genetic disorder aggravated by royal family intermarriage was the House of Habsburg, which inmarried particularly often. Famous in this case is the Habsburger (Unter) Lippe (Habsburg jaw/Habsburg lip/"Austrian lip"), typical for many Habsburg relatives over a period of six centuries. The condition progressed through the generations to the point that the last of the Spanish Habsburgs, Charles II of Spain, could not properly chew his food. (See mandibular prognathism.)

Besides the jaw deformity, Charles II also had a huge number of other genetic physical, intellectual, sexual, and emotional problems. It is speculated that the simultaneous occurrence in Charles II of two different genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis could explain most of the complex clinical profile of this king, including his impotence/infertility which in last instance led to the extinction of the dynasty.

Blake
01-11-2011, 08:21 AM
Hey! Here's a suggestion--perhaps animals who tend to be predatory kick out the females, whereas animals who tend to be prey kick out the males when they come of age. Horse herds for example kick out the males, whereas great apes as has already been stated tends to kick out the females. My guess is that a group of young female prey animals would have a far smaller chance of survival in the wild than a group of young males would; on the other hand, males of more predatory groups tend to rule the roost over females in a way which does not happen nearly as often among prey animals [if at all, fuzzy on the details I just remember my generalities from my "Kratt's Creatures" phase]. Thus the males of predatory groups would be less likely to leave, especially because a young group of female lionesses, for example, would have a much easier time of it trying to survive than a group of young does or impalas or even zebras would.
Just a suggestion--but a sound one, don't you think?

No, it doesn't really hold water.

The most obvious problem is that it is the male lions who are expelled from the pride, not the females. As a result one will commonly find groups of young lions, but never groups of young lionesses. The young lions survive just fine.

Added to that, stallions have a far, far more rigid control over their harem than any lion does.

FuzzyOgre
01-11-2011, 08:36 AM
Ok. so it is possible to over crossbreed a tank of gold fish?

Broomstick
01-11-2011, 09:01 AM
Just curious. Humans have complex social arrangements and to prevent this. How do animals manage to avoid incest and inbreeding??
Other posters have covered how animals manage to avoid incest, or don't, for most large critters.

Oddly enough, some insects not only don't avoid incest, they are pretty much obligated to practice incest. Stephen J. Gould wrote a couple of essays on wasps, aphids, and midges that practice incest either exclusively or occasionally.

Mister Rik
01-11-2011, 11:23 AM
In horses, that is referred to as linebreeding for father-daughter or mother-son crosses, vs. inbreeding for brother-sister crosses. Many hoirse breeders claimed that linebreeding was OK, but not inbreeding.

But from what I know of genetics, I don't see that there is any difference between them.

Some years back, my sister owned a male, purebred Italian greyhound, and on one occasion she sent the dog back to the breeder to provide stud service with his mother. Apparently, this was not out of the ordinary.

OTOH, my sister's "fee" was that she got any males from the resulting litter (turned out to be just one), and that male was probably the stupidest dog I've ever encountered. He got his ass kicked by my mom's cat every time my sister brought him over, and just never learned to leave that cat alone. He was also smaller than typical for the breed.

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