The issue of consanguineous marriage resulting in deformed or abnormal children is one of the concerns we often hear about.
But does this pose a real risk, and is this claim supported by scientific studies and evidence?
Or is it merely a widely circulated belief passed down among people? If this claim is indeed true,
we can observe many individuals around us who are married to their cousins or other relatives,
yet they lead normal lives without experiencing any health issues neither they nor their children.
Consanguineous marriage historically
In 1516, the Habsburg royal family was established in Spain, becoming one of the most sovereign and powerful dynasties in Europe.
Their rule over the Spanish kingdoms lasted from 1516 to 1700, a period of two centuries. In order to maintain their power,
the Habsburg monarchs believed they had to preserve their bloodline's purity, ensuring that they and their descendants would hold power for as long as they lived.
To achieve this goal, King Philip I decided that the Habsburg family would not marry anyone outside their lineage, meaning they would practice consanguineous marriage (marrying cousins).
This tradition of intermarriage continued within the family until 1661, the year when the last and most famous Habsburg king, Charles II, was born ultimately leading to the family's extinction.
King Charles II carried genes resulting from two centuries of inbreeding.
The entire family followed a pattern of intermarriage, deviating from the typical reproductive practices of the general population.
Charles suffered from numerous severe disabilities, the most notable being his inability to speak until the age of four and his inability to walk until he was eight.
He also had a deformed jaw and was infertile. Since he was the last monarch of the Habsburg dynasty, his condition ultimately led to the family's extinction after his death.
After his passing, doctors discovered that his heart was abnormally small, his lungs were deteriorated, and his skull was filled with fluid.
Additionally, he suffered from intestinal issues, irregular pituitary gland hormones, and various other ailments all indicating that Charles was in a state of complete physical devastation.
Over time, the belief spread that consanguineous marriage was the cause of Charles II's severe health problems and, ultimately, the extinction of the Habsburg family. But is this claim true, or was Charles simply a unique medical case?
Looking back in history, particularly in ancient Egypt, consanguineous marriage played a significant role within royal families.
DNA studies have confirmed that Egyptian pharaohs indeed married their own sisters, as seen in the cases of Ahmose and Akhenaten.
This practice persisted despite the fact that incest was legally and religiously prohibited in Egypt.
However, these laws did not apply to the royal family, allowing intermarriage to remain widespread among the ruling class to maintain their grip on power.
In 2015, a study examined 259 adult Egyptian mummies, revealing that royal mummies had noticeably different heights compared to the general Egyptian population.
This means that males were taller than average, while females were shorter than average.
One of the most well-known pharaohs born from consanguineous marriage was Tutankhamun.
When his remains were examined, it was discovered that he suffered from a foot deformity, and his tomb contained 130 walking canes, indicating mobility issues.
Despite extensive research in genetics and the effects of inbreeding, Charles II's case received special attention.
In April 2009, a study was published in the National Library of Medicine titled "The Role of Consanguineous Marriage in the Extinction of a Human Dynasty", specifically referring to the Habsburg family.
The study aimed to analyze the impact and risks of consanguineous marriage, using the Habsburg dynasty as a case study, given that it is one of the most famous examples of royal inbreeding.
When researchers delved deeper into the history of the Habsburg family, they noticed an alarmingly high infant and child mortality rate within the dynasty.
Between 1527 and 1601, the Habsburg family recorded 34 child deaths, resulting in a mortality rate of approximately 30%.
However, despite this significant number of deaths, the researchers remained objective and refrained from immediately attributing the issue solely to consanguineous marriage.
Instead, they began collecting data on eight family lineages within the Habsburg dynasty to conduct a more thorough analysis.
When studying this data, which included 51 pregnancies from 8 families, they found:
- 5 miscarriages
- 6 neonatal deaths
- 14 deaths of adults under 10 years old
With data from 51 pregnancies, alongside studies of marriages outside the royal family, researchers concluded that the primary cause of infant and child mortality before the age of 10 was consanguineous marriage and inherited genetic diseases.
The study continued across multiple generations until reaching Charles II, in whom all the family's genetic disorders had accumulated.
These hereditary conditions caused him numerous internal illnesses and an unusual physical appearance. Inbreeding allowed recessive genes within the family to become dominant, ultimately affecting his health and physical traits.
Natural genetic traits
Genetics specialists explain that genetic traits are stored within the cell, specifically in the chromosomes found in the cell nucleus.
Each chromosome consists of a pair that carries genetic traits one inherited from the father and the other from the mother.
When traits are carried on chromosomes, they can either be dominant (such as brown eyes) or recessive (such as blue eyes).
If both parents carry dominant traits, like brown eyes, the child will inherit brown eyes.
However, if the father has a recessive trait (blue eyes) while the mother has a dominant trait (brown eyes), a genetic "battle" occurs, in which the dominant gene usually prevails, meaning the child will most likely have brown eyes.
In the above cases it is very normal, but where does the problem lie?
The problem arises when both parents carry the same recessive trait. In this case, the child will inherit this trait because there is no dominant gene to override it.
This is precisely what happens with genetic disorders resulting from consanguineous marriage.
Genetic diseases are often recessive traits, and if one parent carries a dominant healthy gene, it can mask the recessive disorder.
However, when both parents share the same recessive trait, there is no dominant gene to prevent the disorder from manifesting in the child.
Does consanguineous marriage produce abnormal children?
Consanguineous marriage can result in children with congenital disorders if both relatives carry or inherit the same recessive gene linked to a genetic disease.
In this case, the child is likely to inherit the disorder, which is where the real risk of inbreeding lies. Therefore, from a theoretical, scientific, and research-based perspective, consanguineous marriage can lead to birth defects in certain cases.
However, many individuals marry their relatives, and their children are completely healthy.
This is because the risks mentioned above only apply when genetic disorders are present.
This brings us to the importance of medical screening before marriage, especially in the case of consanguineous unions, to detect potential hereditary diseases and reduce the risk of genetic disorders in offspring.
Necessary medical examinations before marriage
These medical tests should ideally be conducted for all couples, regardless of whether they are related or not.
They are generally divided into two categories: tests for males and tests for females.
Necessary tests if there is no kinship between the spouses:
For males, they are required to:
- Blood type determination
- Hemoglobin level
- Blood sugar level
- Hepatitis C test
- AIDS test
- Syphilis test
- Semen analysis
For females, they are required to:
- Hormonal tests
- Rubella virus test
- Blood typing
- Hemoglobin level
- Blood sugar level
- Hepatitis
- AIDS
- Syphilis test
Premarital examinations for males and females in the event of a kinship between the spouses:
It includes the same tests as above, but in addition to two additional tests:
- Chromosome analysis
- Thalassemia analysis
Although some may perceive these tests as numerous, they are actually quite simple.
Through these screenings, potential health risks can be identified and prevented, eliminating any concerns, stress, or complications.
This way, individuals can confidently marry a relative without any doubts or fears regarding genetic health risks.