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Inbreeding is defined as the mating of organisms closely related by ancestry. In this instance, we are looking at human inbreeding.
Inbreeding goes against the biological aim of procreating, which is the mixing of DNA.
Human DNA is arranged into 23 pairs of chromosomes. Within each chromosome there are hundreds of thousands of genes.
Each gene has two copies known as alleles, or matching genes; one from our biological mother, one from our biological father.
Genes determine every aspect of our appearance. They contain the information that decides a person's specific physical and biological traits, like hair color, eye color, and blood type. In other words, a gene is the basic physical and functional unit of heredity.
These genes fall into two categories: dominant and recessive.
What's the difference between dominant and recessive genes? If one of the genes in the pair is dominant, then the result is you gain the trait of the dominant gene. However, for traits that originate from the recessive gene, you need both genes to be recessive. Here are some examples.
Remember, genes contain the information that determines a person's specific physical and biological traits. So for example, the gene for brown eyes is dominant and so having just one of these in a pair will result in your eyes being brown. However, the gene for blue eyes is recessive so you'll need both of them to get blue eyes.
Similarly, genetic factors appear to play a major role in determining hair texture—straight, wavy, or curly—and the thickness of individual strands of hair.
Certain congenital defects and genetic diseases are carried by recessive genes. These disorders include cystic fibrosis, sickle cell anemia, and Tay-Sachs disease (a rare, inherited disorder that is characterized by neurological problems caused by the death of nerve cells, or neurons).
Blood-relative mating partners have similar DNA. Therefore the likelihood of them carrying the same recessive gene is greatly increased.
That being the case, inbreeding escalates the chances of being born with such conditions.
In fact, according to a study published by the National Library of Medicine, the rate of near natal and childhood death increases if the child comes from a first cousin union, a so-called consanguineous marriage.
As previously outlined, the odds of inheriting rare genetic diseases goes up exponentially among children who are the result of human inbreeding.
Inbred children often display decreased cognitive abilities and muscular function, reduced height and lung function, and are at greater risk from diseases in general.
Research has indicated that the effects of inbreeding in humans continue into adulthood, further promoting physical and mental disorders.
Inbreeding has been found to decrease fertility. Fetuses produced by inbreeding also face a greater risk of spontaneous terminations due to inherent complications in development.
Consanguineous parents also possess a high risk of premature birth and producing underweight and undersized infants.
Genetic disorders due to inbreeding include blindness, hearing loss, neonatal diabetes, and limb malformations.
Consanguinity has even been suggested as a risk factor for the development of schizophrenia in offspring.
Inbreeding was certainly commonplace in antiquity. In the case of the pharaohs of ancient Egypt for example, the custom not only kept traits within a bloodline, it prevented another family marrying in and lining up to take the throne. In fact, inbreeding propagated power.
Royal intermarriage was often practiced among European royal families, usually for interests of state. Likewise, inter-nobility union was used as a method of forming political alliances among elites. Pictured is Philip II of Spain and his wife, Mary I of England, who were first cousins once removed.
So commonplace was intermarriage within the House of Hapsburg that the Hapsburg lip (or the Hapsburg jaw, as it's also known) was often cited as an ill-effect. The condition is today known as prognathism, an extension or bulging out (protrusion) of the lower jaw (mandible). In this 17th-century portrait of Charles II of Spain, the disorder is clearly evident.
Today, cultural taboos, parental education, and greater awareness of inbreeding consequences have played significant roles in minimizing inbreeding frequencies in areas like Europe. But the custom is still practiced in other regions of the world.
It's estimated that one billion of the current global population live in communities with a preference for consanguineous marriage.
Consanguinity is a deeply rooted social trend among one-fifth of the world population mostly residing in the Middle East, West Asia, and North Africa.
But even in these regions there is mounting public awareness on prevention of congenital and genetic disorders in offspring due to inbreeding.
And evidence suggests that an increasing number of couples contemplating marriage and reproduction in highly consanguineous communities are seeking counseling on consanguinity.
See also: Pregnancy myths people still believe
Inbreeding has probably been practiced for millennia, geneticists believe. For thousands of years our ancestors, including Neanderthals, lived in small, isolated populations, leaving them severely inbred, according to genetic analysis published by New Scientist.
Inbreeding is the mating of individuals or organisms that are closely related through common ancestry. In humans, it's associated with consanguinity, defined as a union between two individuals who are related as second cousins or closer. History records that inbreeding was commonplace in antiquity, and probably even earlier. Today, cultural taboos, parental education, and greater awareness of inbreeding consequences have played large roles in minimizing inbreeding frequencies in Europe and throughout the Western world. But the custom is still practiced in other regions of the globe, and the health risks of doing so remain serious. But what exactly are the inherent dangers of human inbreeding?
Click through and find out what happens when you go against the biological aim of procreating.
The inherent dangers of human inbreeding
The complex issues surrounding consanguinity
HEALTH Relationships
Inbreeding is the mating of individuals or organisms that are closely related through common ancestry. In humans, it's associated with consanguinity, defined as a union between two individuals who are related as second cousins or closer. History records that inbreeding was commonplace in antiquity, and probably even earlier. Today, cultural taboos, parental education, and greater awareness of inbreeding consequences have played large roles in minimizing inbreeding frequencies in Europe and throughout the Western world. But the custom is still practiced in other regions of the globe, and the health risks of doing so remain serious. But what exactly are the inherent dangers of human inbreeding?
Click through and find out what happens when you go against the biological aim of procreating.