Okay so during and after the time of Jesus, it was okay for people to marry their relatives. People married their half sister or brother. Even in the 1500s royal families still married their relatives in England. So then how did the the law of not being able to marry close family members come about? Is it something that people eventually saw as wrong and decided to stop? Was it because of genetic diseases? This could also deal with sociology. Is there just a huge population that now more countries are not allowing marriage between relatives?

Well, I wonder what all this has to do with Christianity?

Christianity does not have anything to do with marriage. Marriage is based on customs, which sometimes evolve to law.
So, I am wondering what your question is.

Be sure to check all the reference notes at this site. It will give you a good place to start in your research.

http://en.wikipedia.org/wiki/Marriage

Marriage has to do a lot with religion, Bob. Religion is a big part of cultural customs and traditions.

LOL, Matt, I beg to differ. Historically, marriage has been a legal union, sometimes to join two families for power purposes; sometimes to legalize the union and children from that union. Religion has only become an important part of many marriages in relatively "modern" times. Check that site I posted. Very interesting history.

But still, is it not fair to say that those cultures still had a strong religious influence? Religions are very deeply intertwined into cultures.

The shift in attitudes towards marrying close relatives over time derives from multiple factors, including social, cultural, and scientific reasons. Allow me to explain the evolution of this practice.

In many ancient societies, including ancient Egypt, Greece, and Rome, marriage between relatives such as half-siblings, cousins, or even full siblings was permitted and, in certain cases, even encouraged. This was often due to dynastic or political motivations, as marrying within the family helped consolidate power and maintain bloodlines.

As societies progressed and advanced, different factors contributed to the changing perspective on incestuous marriages. Sociological and cultural influences played a significant role. As religious beliefs and moral values developed, societies began to view incestuous relationships as taboo or morally wrong. The understanding of family structures and the social implications of marrying relatives expanded, leading to a shift in social norms.

Scientific advancements in the study of genetics and heredity also played a crucial role in shaping this shift. Researchers discovered that close relatives have a higher likelihood of sharing harmful genetic traits or carrying recessive genes that, when paired with another close relative, could lead to an increased risk of genetic disorders or diseases in their offspring. This discovery raised concerns about the potential harm to future generations and further reinforced the move away from incestuous marriages.

In response to these changing societal views and scientific discoveries, various countries established laws and regulations restricting or prohibiting marriages between close relatives. These laws aim to protect the health and well-being of future generations by reducing the risk of genetic disorders. Additionally, they help maintain social and cultural norms that have developed over time.

It's worth noting that different countries have different degrees of restrictions on cousin marriage or other forms of close kin marriage. Some countries completely prohibit such marriages, while others allow them under certain circumstances or with specific caveats.

In conclusion, the evolution of attitudes toward marrying close relatives is influenced by a combination of sociological, cultural, and scientific factors. The emergence of religious and moral values, advancements in genetics, and concerns about potential health risks have all contributed to the implementation of laws and societal taboos against close kin marriages in many parts of the world today.