The Catholic Churchhas a reputation for strict unbending theology, but it may have inadvertently triggered the non-conformist and individual culture of today’s western societies, researchers believe.
Academics now believe that rules enshrined in canon law in the 9th century, which limited the marriage of relatives to prevent incest, fundamentally changed the culture of Europe, breaking apart old clans and ushering in a new era of cooperation.
Western societies are generally viewed as quite odd by sociologists because they tend to view individuals as more important than the group, they conform less to a central ideal and they have a far greater trust of strangers.
In contrast, older more traditional societies tend to comprise tight-knit tribes where members show fierce loyalty, obedience, adherence to tradition and a general mistrust of outsiders.
Until now, academics had been puzzled as to what caused the transition, but they have now discovered that areas that were early adopters the Medieval Catholic Church marriage rules transitioned into modern western societies.
The rules forced communities to cast their net wider for marriage partners, splitting apart tight networks and opening up a new pattern for society in which outsiders and new alliances were embraced.
Professor Joseph Heinrich, chair of human evolutionary biology, at Harvard University, said: “The Western Church in Europe, the branch of Christianity that eventually evolved in the Roman Catholic Church had transformed human society from the grassroots by dismantling the intensive kin-based institutions, leaving much of Europe with monogamous nuclear families.
“And monogamous families are vanishingly rare outside of Europe in an anthropological perspective.
“The longer the duration under the church will predict greater the individualism, less conformity, obedience and more cooperation and trust with strangers.”
Until the medieval period, the church restricted marriages to very close relatives such as parents, siblings and first cousins.
But by the 9th century it has widened its scope up to sixth cousins and even non-related spiritual kin like godparents, leaving communities to search for marriage partners far outside their families.
The church was so preoccupied with incest that natural disasters such as the plague were said to be God’s punishment for the sin.
By the 12th century banns of marriage were made compulsory so that couples could be investigated for familial links, while wedding congregations began to be asked if they knew of any impediment why the marriage could not take place.
Dr Jonathan Shultz, assistant professor of economics at George Mason University, one of the authors of the new research, added: “I was surpised just how preoccupied medieval Europe was with the fear of incest. Historians also talk about an obsession with incest.
“This fear was not only about incest with close relatives but included an ever-exapnding circle of cousins, in laws, spirtial kin such as godparents and godchildren. Natural disasters such as the plague were attributed to God’s punishment for incest.
“There is good evidence that Europe’s kinship structure was not much different from the rest of the world before the church instituted its marriage prohibitions.”
The team studied records kept by the Catholic Church throughout Europe which showed it’s growing influence from the Medieval period. They also looked at Vatican archives recording the number of cousin marriages in the regions.
They also measured psychological trends, such as kindness to strangers by looking at blood donation records. They found that in areas such as southern Italy, where the church held sway for a shorter period, and cousin marriage was higher, blood donation was lower, in comparison to the North.
Today in non-Christian countries that do not share western principles, such as Iran, Afghanistan and Pakistan the rate of cousin marriage is still between 30 and 60 per cent.
Iranian born Duman Bahrami-Rad, a post-doctoral researcher from Harvard, who helped with the study added: “When I moved to Canada to do my PhD there, I was so surprised to discover Canadians don’t marry their cousins. I thought it was weird that westerners don’t fall in love with their cousin.”
Sociologists dub Western populations as ‘Weird’ which stands for western, educated, industrialised, rich and democratic, because they are so strikingly different to traditional societies.
The research was published in the journal Science.