The idea that marrying first cousins is harmful is very doubtful, but even if there is some harm in it, opposing it totally requires a very narrow, Western, materialistic, and individualistic perspective given the benefits.

The belief that marrying cousins is harmful arose in a context where there was intense inbreeding for multiple consecutive generations, often by cousins who were closely related on both the paternal and maternal sides.

The main motivation for this was the preservation of wealth and power within a single dynasty.

As is often the case in the West, they swung from one extreme to the other, until it reached the point where they even banned marriage to sixth cousins, which ultimately eroded family ties and empowered the Church and the State. So there was a clear material motivation.

Modern studies that claim congenital birth defects are higher among couples who are first cousins are extremely flawed. For example, one of the most cited studies was conducted in the UK and looked primarily at Pakistani immigrant families.

The study found that the risk of birth defects was around 6% for children born from cousin couples and around 3%, but there are a couple of factors that were not considered.

One is that most Pakistani households in the UK are what are termed lower income households and that lower income households in general have higher rates of birth defects. Subsequent studies tried to adjust for this, and found that the rates of birth defects were lower, but still higher than in couples that were more distantly related.

Another issue which was not considered in these studies, however, is that many of these families marry cousins for many generations for un-Islamic reasons, and reject outright the possibility of marrying their children to righteous, religious spouses outside of the family completely.

Furthermore, since jihad has been abandoned for generations there is no more influx of slaves to bring diversity into the gene pool. More expensive, Westernized lifestyles also limit family size, meaning that families who consistently and exclusively marry cousins draw from an ever shrinking genetic pool.

Many or perhaps most of the families included in these studies fit this description, and none of these studies consider how many generations these families have been marrying cousins and what their attitudes toward marrying outside of the family are. Unfortunately many families who marry cousins have extremely hostile attitudes toward other tribes, nationalities, and races, which over generations could augment the risk factors associated with cousin marriage.

Still, even with all the flaws in these studies, the increased risk of birth defects is similar to the risk associated with women delaying pregnancy until later in life, and yet none of these people ever criticize women delaying pregnancy in order to pursue careers.

When it comes to technologies which are strongly linked to birth defects such as synthetic fertilizers, pesticides, and pharmaceutical medications which inevitably leech into the water supply, somehow they view this increased risk as acceptable due to the perceived benefits.

These individualists also don’t consider the benefits of cousin marriage when weighing harms and benefits, and this is because most of these benefits are based in factors that they don’t consider in their narrow, almost autistic style of analysis.

For example, cousin marriages are less likely to end in divorce, probably because people from the same family and culture have similar values and often higher compatibility, which can mean less stress and conflict in many cases.

It also reinforces a strong and clear sense of cultural identity, which is associated with many positive mental and physical health outcomes.

Cousin marriages also have higher rates of fertility than non-cousin marriages, so even if a a child is born with birth defects there is likely to be more children to help care for their sibling.

Finally, and most importantly, Muslims understand that there is a purpose and a plan behind illness and disability. It reminds us of our weakness, causes us to turn to Allah for help, and helping to care for the sick or disabled with patience is a source of great reward with Allah. Disabled people may also have spiritual or emotional value which makes up for any physical or mental weakness they have.

We do not, thus, regard the sick or disabled as unwanted, defective, or inferior.

Viewing the disabled as inferior or unwanted causes massive psychological harm to them, which in turn harms the surrounding society, and this happens frequently with the kuffar.

The benefits of cousin marriage are more difficult to quantify, so the kuffar shift the focus toward what they are able to measure, part of their quest for omniscience and to actualize a theology in which human beings are elevated to the level of Allah.

On the other hand, Muslims who abandon Islamic marriage guidelines, focus excessively on cousin marriage, adopt prejudicial attitudes toward other tribes or ethnicities, and close themselves off to the rest of the ummah may be helping feed the narratives of the enemies of Islam.

May Allah guide us and make us steadfast upon Islam, which is a balanced way of life, and protect us from the excesses, imbalance and extremes of shortsighted and flawed manmade ideologies that foolishly exalt human perception and logic above revelation.