Talk:Inbreeding

	This article is part of WikiProject Genetics, an attempt to build a comprehensive and detailed guide to genetics on Wikipedia. If you would like to participate, you can edit this page, or visit the project page to join the project and/or contribute to the discussion.
???	This article has not yet received a rating on the quality scale.
???	This article has not yet received an importance rating.

	This article is part of WikiProject Evolutionary biology, an attempt at building a useful set of articles on evolutionary biology and its associated subfields such as population genetics, quantitative genetics, molecular evolution, phylogenetics, evolutionary developmental biology. It is distinct from the WikiProject Tree of Life in that it attempts to cover patterns, process and theory rather than systematics and taxonomy. If you would like to participate, there are some suggestions on this page (see also Wikipedia:Contributing FAQ for more information) or visit WikiProject Evolutionary biology.
Start	rated as start-Class on the assessment scale
High	rated as high-importance on the assessment scale

To-do list for Inbreeding:	edit · history · watch · refresh
Add some more images - for example a graph of heterozygosity decrease over generations depending on relatedness Improve references - inline citation would be better Hamilton's theory of inbreeding and eusociality in termites
Priority 3

[edit] Westboro Baptist Church

Why was this even included? Westboro Baptist Church

The church group (and alleged cult) Westboro Baptist Church has apparently begun inbreeding, with one of its members, Rachel Phelps, being married to her nephew's brother-in-law, Charles F. Hockenbarger (her newphew, Samuel Phelps-Roper, is married to Charles' sister, Jennifer). Additionaly, though it does not interfere with genetics, Shirley Phelps is married to her step-brother, Brent D. Roper. Long before these marriages took place, residents of Topeka speculated that the church's stringent guidelines against marrying outsiders, coupled with the lack of potential spouses within the group (nearly 90 of the group's 100 members are related through blood or marriage) would lead to eventual inbreeding. It is unknown whether this pattern will continue or, if it does, how extreme the degrees of inbreeding will become.

There is no genetic relationship in the above case. Anything else is speculative. Phelps is married to her adopted brother if you read the article on Roper. Whatever our own feelings about the church, I think that bit doesn't add to the article and wasn't motivated by a desire to improve the article.

Comatose51 18:54, 23 October 2005 (UTC)

[edit] Endogamy merge?

How about merging this article with the endogamy article? Maybe the inclusion of the Ashkenazim, also.

Moved this here.

Inbreeding also occurs in humans. For example, Japan is one of the most endogenous societies in the world.

It doesn't seem clear to me that 1) Japan is more endogenous than say Iceland and 2) this can be regarded as inbreeding since the rate of genetic and health problems in Japan isn't higher than the rest of the world.

"one of the most" :teach: 74.225.130.13 23:01, 22 March 2007 (UTC)

I don't care who is singled out but I do need at least one example of it in humans.

From the link I gave:

One of the most endogenous societies in the world, Japan has approved of incestuous marriages in court circles even in historical times.(152) Preferred sibling, cousin, uncle-niece and aunt-nephew marriages have been so extensive that genetics experts have discovered that the inbreeding has affected their size and health.(153) How often this incestuous marriage system occurred in traditional Japan is still largely unexplored. One indication of what is likely to be found is a 1959 study by Kubo showing that there were still rural areas in Japan where fathers married their daughters when the mother had died or was incapacitated, "in accordance with feudal family traditions.(154) Kubo concluded that incest was considered "praiseworthy conduct" in many traditional rural families. In the 36 incest cases he studied in Hiroshima, he found that there was often community moral disapproval of the families who lived in open incestuous marriages, but that the participants themselves did not think of it as immoral. In fact, when the father was unavailable to head the family, his son often took over his role and had sex with his sister in order "to end confusion in the order of the home." Other members of the family accepted this incest as normal.

1) Consider the possibility that you can't find an example because there isn't one.

2) Japan has a population of 150 million. Finding a few dozen or even a few thousand cases of incest isn't near enough to label the population as inbreed.

No way. Incest is very prevalent in Japan. It's a question of finding a population that's inbred.

There should be something about inbreedding depression, and perhaps something about breeding culture with animals, where they recommend an inbreeding coefficient around 1-5% as far as I remember. Outbred isn't always recommended.

This whole paragraph needs rewriting:

The only really major problem with inbreeding is that two closely related individuals are likely to have very similar genomes, and if one individual has a gene for a given negative trait, then the other is likely to have it as well. It is pretty complex, and I would spew numbers, but I'm sure any reasonably intelligent person can figure it out for themselves with a basic knowledge of Gregor Mendel and his plant breeding experiments. Suffice it to say that a single instance of inbreeding is statistically very unlikely to result in a flawed individual.

-- The Anome 09:09, Jan 26, 2005 (UTC)

[edit] External link

I wonder about the link Consanguinity and Mating. While it's got a lot of historical anecdote, it needs at least some kind of context as it comes from the site for Anthony M. Ludovici: not exactly a mainstream take on the subject!

I agree, and I've removed it. --Xyzzyplugh 01:00, 13 February 2006 (UTC)

[edit] Jewish Law

In Jewish law it is not incestuous for a man to marry his brother's daughter, but does the same apply to marriages between a man and his sister's daughter? The reason this occurs to me is the definition of a Jew as being a person "with a Jewish mother". This suggests a previous matrilineal kinship system, where those related through the female line might be forbidden to marry, but those related only through the male line were not. Can anyone give further information? Too Old 09:45, 9 January 2006 (UTC)

[edit] Pignatelli case

Erm, not highly relevant to its subheading, since they were not royalty.

Anyway, there have been better examples, for example uncle-niece or aunt-nephew marriages.

Pignatelli was a case of extraordinary generational differences of descent found in some alliances among royalty and nobility. I can rename the heading. Charles 16:28, 27 April 2006 (UTC)

[edit] Outbreeding

"Outbreeding" is linked in the article, but redirects here! The word is not explained in this article, but one could assume[1] that it is the opposite of inbreeding.

Should

• the link be removed,
• a new article created,
• an inline definition be added,
• or, a link to something similar (i.e. Miscegenation) be inserted?

(No, I'm not bold!) CAD6DEE2E8DAD95A 16:58, 9 May 2006 (UTC)

[edit] Charles & Diana

they are left off the list as is the other royals.. Charles & Diana are 3rd cousins.

No, they are not. Their closest relationship is of 7th cousins, once removed. It is non-notable as many, many, many people are related to that degree or closer. Charles 16:29, 11 May 2006 (UTC)

[edit] Editing

I've done a fair bit of rearranging and added a small amount of material I think it makes more sense now, and am removing the tag. --Michael Johnson 12:20, 11 July 2006 (UTC)

[edit] POV?

Intermarriage in European royal families is no longer a problem, due to modern science and our understanding of the negative consequences

Does this sound a little POV to anyone? I understand what they're trying to say, but it sounds a bit off to me.--Stella luna 18:32, 27 July 2006 (UTC)

Yes, it is POV. It is widely assumed, but without any reliable evidence, that intra-marriage among royal families caused genetic "problems", e.g. in King Charles II of Spain and the so-called Habsburg lip. But no one ever cites what precise medical condition caused the problem, nor how it was caused or aggravated by inbreeding (rather than, say, multiple-generation inheritance of a dominant gene) -- and the Habsburg lip is not usually a "problem" at all. Rather, people tend to assume that if a person has an observable defect, and if that person has inbred ancestry, then the deleterious trait must be due to the inbreeding -- mistaking correlation for causation. Whereas we know, due to subsequent improved genetic and medical information, that in famous cases where it was popularly assumed that inbreeding was the source of a congenital defect, it had nothing to do with inbreeding: For example, the historically disastrous hemophilia among the descendants of Queen Victoria of the United Kingdom and her husband/first cousin Albert, Prince Consort. Despite frequent intra-marriage among that couple's descendants, not a single incidence of royal hemophilia is now attributed to inbreeding. Another example is the mental retardation of Prince François, comte de Clermont (and of his sister, Princess Blanche, born 1962), the heir apparent of the current Orléanist pretender to the defunct French throne. Four of Clermont's paternal great-great-grandparents were first-cousins, plus his mother and paternal grandmother also descended from multiple cousin-intramarriages. Nonetheless the retardation turned out to be due to his wife's infection with toxoplasmosis. And of course, nobody wants to mention in this context the brilliant, irresistable and fertile Cleopatra, who descended directly from seven generations of brother-sister marriages. The correct rule-of-thumb here is not "Don't marry your kin", but "garbage in, garbage out -- yet the reverse is just as likely to be true: matings of healthy relatives may produce healthier offspring." Lethiere 21:13, 8 December 2006 (UTC)

While researching inbreeding in humans, I have found reference to the above comment, along with citations of problems with populations that have high homozygosity. It has also been found that some human populations with isolation, and documented genealogies, are relatively free of genetic illness, even though homogeneous. In humans, however, isolation has not generated the races or "breeds", that some researchers such as Sir Arthur Keith, Coons etc. cited in their writings. The current genomic tracings of humans are indicating (relatively) small genetic diversity throughout our species. We have few progenitors,indicated by our mtDNA and the y chromosome, in comparison to many other animals. I am looking for a reference that indicates that our currently known genetic diversity would optimal for a population of 10,000 individuals. I intend to revise the article further on humans. It needs full revision as it is mostly POV. --Kerheals 19:12, 7 January 2007 (UTC)

Our homozygosity is a function of our youth as a species. When compared with Chimps the most distantly related humans display less genetic diversity than chimpanzee siblings.--Counsel 20:30, 8 January 2007 (UTC)

Youth is a nominative adjective, it is an interpretation of what is found. Technically so are our definitions of what is "human".

In humans, we find such occurences of one male producing millions of descendents through his conquests and raids. This "inbreeding" has produced the y chromosomes AND mtDNA most present in the population. There is NO sign of inbreeding depression in the general population.The radiation of the genetic traits, and its ubiquitous increase of population associated with radiation has caused this. Naill of Noigiallach and Genghis Khan have great expression throughout the population. These warriors and raiders had many "wives" and therefore represent a preponderance across the population. It is NOT so much the youth of humans, but the tendency towards population bottleneck, with subsequent genetic drift of the founding genes have produced this finding. WE reduce our genetic pool by our social conflict. And by the way, so do chimpanzees when they raid other groups adjacent to their home territory.--Kerheals 14:32, 16 January 2007 (UTC)

Mandibular prognathism has not been fully identified as a genetic trait. It is SUSPECTED to be so. The trait has not been identified as either recessive or dominant. It has been found to run in families in Japan as well. [[ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16214628&dopt=Abstract]] --Kerheals 04:35, 30 January 2007 (UTC)

[edit] Natural Selection

It is possible for a population to become inbred without inheriting deleterious traits. For instance the cheetah is a highly inbred species, resulting from a population bottleneck. Many island species are also highly inbred. This is more likely in a population where natural selection is acting. I'm pretty sure natural selection is always happening, it's not something that you can turn off.

I think the answer is Yes, if I understand the question --Michael Johnson 12:34, 4 October 2006 (UTC)

[edit] Domestic Animals

We have what appears to be good information there, however, it should be kept in mind that the goal is description, not advice on how any particular editor believes breeding should be done.--Counsel 20:06, 8 December 2006 (UTC)

[edit] Bad Assumptions

Much of this article is written with the assumption that a breeder is infallible. Take the following paragraph for instance:

"Natural selection works to remove individuals who acquire the above types of traits from the gene pool, therefore many more, in the first generation of inbreeding, will never live to reproduce. In biology, the fittest are those who survive and breed. Over time, with isolation such as a population bottleneck, caused by purposeful (assortative) breeding or natural environmental stresses, the deleterious inherited traits are culled."

Firstly, it is a poor assumption that "many more" of the first generation will never live to reproduce. Tp what organisms does this refer? Brine shrimp? Sea Turtles? Trees? Dogs? People? It is not possible to generalize over such a broad spectrum. The second sentence states that only the fittest survive in biology. This may be true of collage biology courses, but not of all organisms. In nature the fitter animals are more likely to survive and reproduce, but in fact all might survive in any given generation or all might perish. It depends upon what organism and what environment we are talking about. Lab rats with horrible defects might survive, sea turtles in the wild might not. The next sentence states that "assortive breeding" culls deleterious traits, ipso facto. This assumes that the person controlling the breeding is able to identify the traits, knows how to eliminate them, and chooses to avoid them. If this were true even most of the time such things as hip dysplasia would not exist in dog populations. In fact, they are increasing. The omniscient breeder assumption that pervades this article needs to be culled.--Counsel 23:05, 21 December 2006 (UTC)

The omniscient anti breeding status of the previous article was not based in genetics. The fittest in biology may not be the "best" choice or the most beneficial for the survival of the species, the article now fairly presents what the issues are in inbreeding. In the first generation(not necessarily a single breeding, statistics show that no deleterious phenotypes are also probable) of inbreeding deleterious traits are most often expressed, that is a fact in ALL organisms, it is a basic tenet of Mendelian genetics. The article previously made no distinction between the "fittest" in a biological sense and the "fittest" in the sense of survival in terms of "strength" and vigor. It is a theoretical error to assume that the strongest survive. This is not always the case, specifically with recessive deleterious traits. The previous article made an error in terms of its emphasis on the strength and vigor. The fittest in biology are simply those who survive and breed. Casual or "backyard" breeders have been responsible for the over expression of deleterious traits in both cattle and domestic companion animals. Such breeders are not assortative(and therefore not in the best interest of a breed) at all. Assortative breeding must, by definition, take the various genetics views into account, and must include requisite culling, which can be distasteful when we are discussing humans. If a breeder is not aware of the traits, then assortative breeding is an impossibility.The article now discusses how to identify the traits, identifies culling as the means of removal, and identifies the benefits of removal by culling. Culling may be accomplished by either euthanesia , natural death(selection) either in utero or after birth, or by sterilization of those who express genetic illness. The previous versions were far to close to the animal rights view, which is by nature, anti breeding. In fact there were many errors of fact, and presentation of genetics theory, specifically in the discussion of cheetahs. Finally what purpose is the discussion of royal families? A previous talk participant pointed out the errors in the outcrossing paradigm that was present within the arguments. Why is it that no changes were made on the entry? --Kerheals 17:11, 24 December 2006 (UTC)

[edit] Moved The Rothschilds from the article here for verification.

===The Rothschilds=== Among the descendants of Mayer Amschel Rothschild, the founder of the famous financial and banking family, many of the men married their brothers' daughters or cousins related through the male line, neither of which practices is forbidden by Jewish law. They also had the tradition that only male descendants in the male line could participate in the business, though daughters did inherit considerable wealth. These two traditions were a means of keeping the business closely in the family. This was the reason that, in 1901, the Frankfurt branch of the family business was closed when the male line that managed it died out.

Please provide a source. I know the entire article is unverified, but this is rather controversial, especially "neither of which practices is forbidden by Jewish law".--132.69.234.73 14:50, 19 March 2007 (UTC)

[edit] Charles II of Spain

Tagged "Dubious" for assumption without genetic evidence that his negative traits resulted from inbreeding. See Talk:Inbreeding#POV? for specific discussion. Lethiere 05:09, 26 March 2007 (UTC)

I know that it has to be tagged without evidence, but come on ;-) Charles 16:05, 7 April 2007 (UTC)

This debate seems to have died due to lack of interest. I am removing the tag. As Charles II's disabilities are widely attributed to his very inbred lineage, it is unnecessary to tag a photo caption. Someone probably should add a cite sometime, though. Montanabw^(talk) 03:26, 23 September 2007 (UTC)

The "debate" has not died due to lack of interest. Rather its point has been vindicated because no one has supplied the requested documentation of the allegation's accuracy. "As Charles II's disabilities are widely attributed to his very inbred lineage, it is unnecessary to tag a photo caption" is an affirmation of hearsay. But people turn to an encyclopedia to learn whether hearsay is accurate, so it is inappropriate to simply affirm it or squeeze it in merely because it is popular hearsay. At least that is my reading of Words to avoid, Weasel words, and the Bandwagon fallacy. The fact that the unsupported allegation is made in a photo caption makes it no less inappropriate. Several examples of popular but inaccurate historical assumptions about royal inbreeding were cited (at Talk:Inbreeding#POV?) as evidence of why this article should not repeat unsubstantiated genetic rumors. I'm giving the caption a weasel tag. Lethiere 06:30, 23 September 2007 (UTC)

Oh for crying out loud! Haven't you ever cracked a world history textbook? This is about the most classic and well-known example of why first cousins shouldn't marry in all of world history! This is so silly. You want sources, fine. It is most certainly not hearsay, though at the time he was said to be bewitched? Shall we move the reference to the magic article? Sheesh! Spend your time tagging dubious and unverifiable claims, for pete's sake. Stay tuned for sources. What a waste of time. Montanabw^(talk) 07:11, 23 September 2007 (UTC)

Well, well. So it is in history textbooks. And here I never knew historians were experts on genetics. Seems to me that if anything, you just eloquently demonstrated why that shouldn't be here in the first place, unless explicitely labelled as unverified rumour. 80.143.194.197 (talk) 19:36, 17 August 2008 (UTC)

[edit] Mormon

Does anyone have a real source for the following info? Sounds kinda bogus and the reference is pretty old. WLU 14:06, 17 April 2007 (UTC)

Cases involving people of the Mormon faith, (who practice polygamy) who have for generations bred with their direct relatives, (i.e. Mother to son union resulting in a daughter who later has a child by her father/brother) have resulted in cases of a rare disorder known as Throemboangiities Obliterians. Children born with this genetic disorder have deep recessed eye sockets, large protruding foreheads, and in many cases never develop teeth.<ref>UNIVERSA MEDICINA, 1899, p.295</ref>

On top of that, the disorder mentioned is not found on google, but thromboangiitis obliterans is, and it relates to tobacco. Looks like BS anti-Mormon propoganda to me. WLU 14:14, 17 April 2007 (UTC)

You should really do your research before deleting content. I did and found Throemboangiities Obliterians to be a real and bona fide medical disorder resulting from inbreeding of Mormon polygamists. Just simply typing something into "Google" and receiving no results, then saying "Shit, this must be fake" shows a lack of research ability. Shame on you, your the kind of person who makes Wikipedia inaccurate and watered down.

Your change was reverted, as you failed to provide any actual reference. You have not addressed my comments, all you did was revert a change then claim evidence. It's people like you that give anonymous contributors a bad name. WLU 23:49, 20 April 2007 (UTC)

Agree with WLU. It is up to the anon editor to produce a reference for what on the face of it is an outrageous claim. --Michael Johnson 00:21, 21 April 2007 (UTC)

Didn't find anything about Throemboangiities Obliterians but if 'anonymous editor' (or anyone else) wants to add it, I found a source on Reuters today for fumarese deficiency being linked to FLDS (old-school Mormon) inbreeding in Arizona: [2] Happy editing! CanadianMist 15:05, 14 June 2007 (UTC)

[edit] Inbreeding depression

Should we just merge this into the inbreeding article? Unless we get up around 30KB or it becomes disproportionately long, it would be better kept here. Richard001 07:11, 1 May 2007 (UTC)

I'd say merge, it'd give us an excuse to trim down this article. WLU 16:54, 2 May 2007 (UTC)

[edit] Cleopatra

I changed the entry on her in the royalty/nobility section, but there wasn't room to explain why in the summary. This is how the bulk of it read:

"Not only this, but all members of the Ptolemaic dynasty from Ptolemy II on engaged in inbreeding among brothers and sisters, so as to keep the Ptolemaic blood "pure". This was often looked over, or even made more complex when Ptolemies married other Ptolemies who had only a remote connection to the Ptolemaic bloodline (Cleopatra herself was the daughter of a Mithridatid princess)."

Firstly, in general only the kings were permitted to marry, so I changed "members" to "rulers". Secondly, although attempting to trace Ptolemaic bloodlines can make your head explode I don't recall anyone marrying a relative who could even charitably be described as "remote". Thirdly and most importantly, we don't actually know for sure who Cleopatra's mother was. There are several leading candidates, but no Mithridatids among them that I recall. So I deleted the last sentence as it seemed to be making some doubtful assertions. Finally, or actually firstly, I added her regnal number VII. I'm not sure about that, as to people not interested in Egyptian history of the period there was only ever one Cleopatra, and the numeral might actually make people think that someone else is being referred to. Perhaps it should go, but I can't decide.

81.154.197.153 16:45, 18 September 2007 (UTC)

[edit] information available for use in this article

The text in the collapse box below was moved here from the article on incest. It's off-topic and overly detailed for that page, but it might fit in this topic well. It needs copyediting and further sources, but maybe it will be useful if anyone wants to merge it in to this article. --Jack-A-Roe (talk) 04:55, 28 March 2008 (UTC)

[edit] Father-daughter inbreeding as reproductive strategy

Mathematically, what are the merits of father-daughter inbreeding as a strategy for maximum propagation of the father's genes? The progeny of any such union would tend to have 75% of the genes of the father. So, let us assume that there is a certain cost to producing one child (e.g. opportunity cost, costs related to feeding/other upkeep of child, etc.). Let us take two possible scenarios. In both of them, we will presume that the father has already, with an unrelated mate, produced a daughter. In scenario 1, the father again reproduces with an unrelated mate, and his daughter reproduces with an unrelated mate. In scenario 2, the father reproduces with his daughter. For the purposes of this analysis, negative social and legal repercussions are ignored.

1. Result = Two individuals with 50% of the father's genes
2. Result = One individual with 50% of the father's genes, and one individual with 75% of the father's genes

But I suspect there are many other factors here which have not been accounted for, such as the fact that in scenario 1, it is the unrelated mate of the daughter who is likely providing the child's support; which he has an incentive to do, because that child has 50% of his genes. Then there are the age-related fertility aspects which I believe were at one time discussed at ephebophilia. Then there are the potential problems related to inbreeding and recessive genes. Has anyone else done analyses on this subject? Aldrich Hanssen (talk) 15:11, 27 July 2008 (UTC)

You may wish to move this question to either inbreeding or consanguinity. You would probably get a better discussion in those areas.

"Incest" is frequently misinterpreted of the de facto act of sexuality with close relatives, but that is incorrect. It technically means a sexual act that is immoral because it is with close relatives (hence the word root "unchaste"). In a hypothetical nation where marriage of father and daughter or brother and sister is legal and non-taboo, such actions are not "incest."Legitimus (talk) 15:29, 27 July 2008 (UTC)

What is the purpose of this discussion? How would it improve the article? Is this some notable view? from a reliable source? Slrubenstein | Talk 19:48, 27 July 2008 (UTC)

I would imagine that the economy of nature would shed a lot of insight into empirically observed activities. Aldrich Hanssen (talk) 15:47, 30 July 2008 (UTC)

Wikipedia is not the place for original research (see WP:NOR) - thee is no point in discussing something unless it will have bearing on an actual improvement to the article, which means compliance with Wp:NPOV, WP:V and WP:RS. Slrubenstein | Talk 09:56, 31 July 2008 (UTC)

[edit] Merger proposal

Linebreeding should be merged into inbreeding since linebreeding is a form of inbreeding and can be sufficiently included in the inbreeding article. Suntag (talk) 00:37, 10 August 2008 (UTC)

The Line breeding article is unreferenced. Where for example is a citation that the mating of first cousins is a "typical" example of Linebreeding? I'm ok with the article being merged and the Linebreeding article becoming a redirect to this article, but I think if you are going to add a linebreeding section (or paragraph?) then any addition needs to be referenced.--Sting Buzz Me... 01:40, 18 August 2008 (UTC)