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The Applicant Series #16: Interbreeding

The Applicant Series showcases works done by hopeful writers who have applied with inkmypapers over the years. The results and comments will be provided first, followed by the actual essay/report written by the applicant

Applicant’s Results: Failed

Title: Inbreeding among families and communities.

Comments: Borderline pass (but we ultimately did not hire the applicant as her performance during the training program is not good enough).

This is part of a full paper that is done by our applicant for our training program. The applicant did a fairly good job at researching and listing out some important points, but overall we are quite disappointed as she did not follow through with what we taught her during the training program. Some issues we had include the short paragraphs, and the numerous grammatical errors made.

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Cases of inbreeding among families and communities

The Darwins and Wedgewoods are one of the prominent families who were known for inbreeding. Darwin was one of the first experimentalists who demonstrated the adverse effects of interbreeding. Their dynasty has been adversely affected by having high mortality and high cases of illnesses and poor health among their family members. (Berra & Alvarez & Ceballos , 2010)

Ansari muslims of Bhagalpur Bihar are also practicing consanguineous marriages. Nearly 40% of the marriages are consanguineous in nature and marriage between first cousins is most common. The Ansari muslims practice inbreeding because of their embrace of Islam and was said to have been inbreeding for about 8 generations, (Afzal & Shina, 1983).

Hutterites, a small group of Anabaptists are well known for their communal behavior which includes inbreeding.  The Hutterites also have a naturally high fertility rate   (Ober & Hsylop & Hauck, 1999)

In the Philippines, one prominent family known for their interbreeding is the Ayala family. The Ayalas have been residing in the Philippines for 9 generations and had a history of marrying ther first cousins. (Brillantes, 2006)

Inbreeding as Evolutionary Adaptive Strategy for Humans

Despite the conventional belief that inbreeding causes deleterious homozygosity resulting to mortality and morbidity, and less viable offspring, there have been studies that assert inbreeding within reasonable boundaries (i.e. number of inbreeding does not lower the heterozygosity of population) as beneficial to some extent (Leavitt, 2005).  Chesser and Ryman (1986) assert in their study that inbreeding is advantageous under certain circumstances especially when the benefits of inbreeding outweigh the risks of unviable offspring.

Adverse Effects of Inbreeding in Humans

The great hazard of inbreeding is that it can result in the unmasking of deleterious recessives, to use the clinical language of geneticists. Each of us carries an unknown number of genes—an individual typically has between five and seven—capable of killing our children or grandchildren. These so-called lethal recessives are associated with diseases like cystic fibrosis and sickle-cell anemia. (Conniff, 2003)

Most lethal genes never get expressed unless we inherit the recessive form of the gene from both our mother and father. But when both parents come from the same gene pool, their children are more likely to inherit two recessives. (Conniff, 2003)

Inbreeding can cause serious health problems, because it increases the chances of successful gene expression for diseases otherwise rare or muted in an individual’s pedigree. (Ceballos, et.al.,2010)

Inbreeding is significantly positively correlated with increased pre-reproductive mortality (rates of fetal loss). (Hauck, et.al.,1999)

Ceballos’ study on the Darwin/Wedgewood dynasty suggests that the high childhood mortality experienced by the Darwin progeny (3 of his 10 children died at age 10 or younger) might be a result of increased homozygosity of deleterious recessive alleles produced by the consanguineous marriages within the Darwin/Wedgwood dynasty. (Ceballos, et.al.,2010)

A statistically significant positive association between childhood mortality and inbreeding coefficient among the 25 Darwin/Wedgwood families was detected. (Ceballos, et.al.,2010)

As a consequence of consanguineous marriage, Darwin’s children had an increased risk of suffering the effects of detrimental recessive alleles, which is a characteristic effect of inbreeding. It is known that three of Charles Darwin’s six children with long-term marriage history suffered from infertility. (Ceballos, et.al.,2010)

IQ of inbred children (8-12 years old) is found to be lower (69 in rural and 79 in urban populations) than that of the outbred ones (79 and 95 respectively). The onset of various social profiles like visual fixation, social smile, social seizures, facial expression, and hand-grasping are significantly delayed among the newly-born inbred babies. (Sinha, 1983)

 The inbreeding theory asserts that the mating of close kin produces bad results, such as abnormal, enfeebled, or insufficiently numerous offspring. The incest taboo is therefore adaptive because it limits inbreeding, and arose on that account. (Aberle, et.al.,n.d.)

Ober, Hyslop and Hauck (1999) found in their study that Hutterite women who were more inbred were also less fertile, implying a recessive trait of low fertility in these women. They concluded that although these women had longer interbirth intervals, there was not an increase in the rate of fetal loss. They also inferred that in these cases where the parents are most likely to pass on less of their genes to their offspring, the recessive allele could well be eliminated. Ochap (2004) also asserts the same idea that “frequent exposure of recessive alleles to selection” will eventually result in its elimination from the population. Another benefit of inbreeding is the reduction of harmful recessive traits, the genetic load, in a population; especially when severe inbreeding is practiced (Barrett and Charlesworth, 1991). In another study, inbreeding was proven to be the answer against epidemics. Inbreeding developed and honed the immune system of past populations against local diseases and epidemics prevalent at the time. However, these also made them vulnerable to foreign viral and parasitical diseases. (Buunk, Fincher, Hoben, Schaller, and Thornhill, 2010) A similar study on consanguinity and breast and cervical cancer by Bener and Denic (2001) showed that having consanguineous parents reduced the risk of getting breast cancer especially for the younger women while no effect was found on cervical cancer.


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