Inbreeding

{{sex}}{{hatnote|This article covers genetically homogeneous breeding amongst plants and animals. For a focus on humans, see [[incest]].}}

'''Inbreeding''' is the mating of two organisms (often animals) that are closely related to each other, and often refers to the continued practice of this, producing inbred animals. It can be used to create offspring with specific desirable characteristics, as in the case of pedigree dogs, cats, or racehorses, but it also occurs naturally in relatively small and isolated populations of animals (including humans, of course). Inbreeding may occur if few people have a disproportionate number of children in a community, as is common in [[Polygamy|polygamous]] societies and those isolated from the wider population. In the case of humans, inbreeding is most commonly associated with [[incest]].

==Benefits and motivations==
[[Image:Cheesy valentines.jpg|right|thumb|Happy mother's day! Ew.
And spelling error, yuck.]]

===Encouragement of desirable traits===

Inbreeding can be used as a method of [[artificial selection]] to selectively breed plants and animals with desirable traits. An example of this would be the breeding of pedigree dogs. Inbreeding may lead to a highly specialised genome, such as in the case of the [[cheetah]] — a species of cat that is heavily inbred, claimed to have been caused by a [[Population bottleneck|catastrophic drop in population that occurred thousands of years ago]]. The species is highly specialized, yet possesses a relatively weak immune system.<ref>[http://www.nytimes.com/1992/11/10/science/cheetahs-appear-vigorous-despite-inbreeding.html?pagewanted=1 Cheetahs Appear Vigorous Despite Inbreeding]</ref>

Ironically, incest is vital to the development of extreme traits in prized domesticated {{wpl|angiosperms}} and animals — offspring in this process are referred to as {{wpl|Hybrid (biology)|hybrids}} from a {{wpl|Taxonomy (biology)|taxonomic viewpoint|.}} Because a few generations of interbreeding can lead to a variety of genetic problems, "out breeding" is performed to remix the genes a bit — farmers may also just buy new seeds outright instead of using their own from the harvest. While farmers do inbreed plants, flower plants have a mechanism to prevent {{wpl|self-fertilization}} in a process called {{wpl|Self-incompatibility in plants|self-incompatibility|.}} In this process, the plant will literally poison pollen it detects as its own with a poison called {{wpl|Ribonuclease|S-RNase}}.<ref>https://www.nsf.gov/news/news_summ.jsp?cntn_id=105840</ref>

Hybrid breeding has yielded an increase in nutritional value among plants;<ref>{{cite journal|last=Bänziger|title=Breeding for drought and nitrogen stress tolerance in maize: from theory to practice|journal=From Theory to Practice|year=2000|pages=7–9|url=https://books.google.com/books?hl=en&lr=&id=HlluklozxuQC&oi=fnd&pg=PA6&dq=B%C3%A4nziger,+M.+(2000).+Breeding+for+drought+and+nitrogen+stress+tolerance+in+maize:+from+theory+to+practice.+&ots=EFYvA-K68C&sig=cTWng_6xt1H8W4io_tD9XVvduJc#v=onepage&q=B%C3%A4nziger%2C%20M.%20(2000).%20Breeding%20for%20drought%20and%20nitrogen%20stress%20tolerance%20in%20maize%3A%20from%20theory%20to%20practice.&f=false|accessdate=7-11-2013}}</ref> part of this is can be accounted for by the fact that plants are much easier to interbreed than animals due to plants having a higher fertility rate.

===Applications in genetic research===

Inbred strains of species are important in genetic research. Inbreeding creates a less varied genome, reducing the chances that a genetic variation among test subjects could skew their results.

==Drawbacks==
===Loss of diversity in the genome===

A loss of diversity may leave a group less adaptable to changing circumstances - creating a genetic monoculture. In the case of plants, this increases the risk that crops would be eliminated by a pest or disease for which the entire group lacks resistance. An example of this is found in the Irish potato famine, in which two factors led to mass starvation: an artificially imposed over-reliance on a single crop (potatoes), and a lack of variety in that crop.<ref>[http://evolution.berkeley.edu/evolibrary/article/_0_0/agriculture_02 Irish Monoculture and the Irish Potato Famine: cases of missing genetic variation]</ref>

===Recessive traits and genetic abnormalities===

Recessive traits are traits coded for by recessive alleles. Recessive alleles are variants of genes that are "switched off" or overridden by the presence of a dominant allele of the same gene: Therefore, a recessive trait will only be expressed if an individual carries only recessive alleles for that trait's gene(s). Close relatives are much more likely than strangers to carry the same alleles, increasing the chances that their offspring could inherit recessive alleles from both parents. Recessive traits may be cosmetic, such as in the cases of blue eyes and red hair,<ref>[http://genetics.thetech.org/ask/ask44 Hair Color]</ref> or more serious, carrying mutations leading to genetic abnormalities or diseases such as hemophilia or cystic fibrosis <ref>[http://ghr.nlm.nih.gov/condition/cystic-fibrosis Cystic Fibrosis at Genetics Home Reference]</ref>.

In animal breeding, the bulldog is commonly cited as an example of inbreeding taken to a point that the animal could not have otherwise reached by [[natural selection]]. Bulldogs have been bred for their characteristic floppy face, but in some dogs this has reached point at which dogs may struggle to breathe. The UK Kennel Club, an organization for dog breeders, issued guidelines to limit the breeding of that specific characteristic.<ref>[http://www.timesonline.co.uk/tol/news/uk/article5512620.ece Healthier new bulldog will lose its Churchillian jowl]</ref>

==Royalty and inbreeding==
[[File:Carlos segundo80.png|thumb|When you're descended from {{wpl|Joanna of Castile|"Joanna the Mad"}} in ''fourteen'' different ways, you're not off to a good start in life.]]
The royal families at various times went in for inbreeding for dynastic and other purposes; a child born to two Royals would have an arguably stronger claim to the throne, and this also reduces the number of cousins and second cousins in an ever expanding family that would fight amongst themselves over every last scrap of the empire.  Notable examples are the Pharaohs of Ancient Egypt (brother-sister marriage — though secondary wives were also involved, giving some mixture to the gene pool) and {{wpl|Charles II of Spain||.}}

The ruling classes of some societies have tried to breed with those of a similar high status. In Europe, it was common for the royalty of various nations to be related by blood, the House of Windsor being an example of this.<ref>[http://www.royal.gov.uk/pdf/Windsor%20family%20tree.pdf Windsor family tree (PDF)]</ref>  But with the number of Royal families being limited to ''at most'' the number major empires in existence, it's not long before every significant King and Queen are cousins with each other.  Queen Victoria, for instance, was the grandmother of George V, Kaiser Wilhem, and of Tzar Nicholas II's wife.  Victoria's husband was also her first cousin as well.

This inbreeding is comparable to [[eugenics]], in that certain bloodlines are deliberately kept "pure". In practice, it often resulted in the opposite of eugenics, producing such benighted creatures as Charles II of Spain, whose jaw was so deformed that he couldn't chew his own food and could barely speak.<ref>[https://io9.gizmodo.com/a-family-in-spain-displayed-three-generations-of-the-h-1679771704 A Family in Spain Displayed Three Generations of the "Habsburg Jaw"]. ''io9''</ref> The House of Habsburg, an Austrian dynasty that held thrones across Europe, notoriously engaged in reckless amounts of inbreeding to ensure that the family's assets stayed under their descendants' control.<ref>[https://allthatsinteresting.com/habsburg-jaw The Habsburg Jaw And The Cost Of Royal Inbreeding]. ''All That's Interesting.''</ref> This eventually backfired on them, as the catastrophically disabled Charles II was sterile and died without an heir, sparking the War of the Spanish Succession.<ref>[https://allthatsinteresting.com/charles-ii-of-spain This Inbred Spanish King Was “So Ugly” He Scared His Own Wife]. ''All That's Interesting.''</ref> Also known to [[snark|snarky people]] as the "War of the Inbred Idiot", the War of the Spanish Succession lasted 12 years and resulted in the end of the Habsburg monarchy there as well as the crumbling of Habsburg holdings in Central Europe.<ref>{{wpa|War of the Spanish Succession|}}</ref> Spain entered its Bourbon period after that.<ref>[https://www.newtravelservices.net/en/42-51-content/sicily/sicilian-history/spanish-bourbon-period Spanish Bourbon Period]. ''New Travel Services.''</ref> Who can blame them?

One general result of this inbreeding in the European royal families was the concentration of the disease hemophilia in the males.<ref>[http://www.englishmonarchs.co.uk/haemophilia.html Haemophilia in the Descendants of Queen Victoria]</ref> So much so that hemophilia was known as the Royal disease until after World War II.

==See also==

*[[Incest]]
*[[Bestiality]]
*[[Genetics]]
*[[Sexual reproduction]]
*[[Artificial selection]]
*[[One-drop rule]]

==External links==
*[http://www.imdb.com/title/tt0112365/usercomments?filter=prolific Angels and insects] at IMDB
*{{wpa|Charles II of Spain}}

==References==
{{reflist|2}}

[[Category:Genetics]]
[[Category:Culture]]
[[Category:Incest]]

Categories: Genetics, Culture, Incest