In current middle-east societies, cousin-to-cousin marriage is not considered incest, and is completely acceptable.
This seems to be the norm for many ancient societies, from Europe to Asia.
At what point in history did this shift take place? and is there any reason for western society taking this position?
Most Western societies do not consider marriage between first cousins to be legally invalid, or incest.
As far as I can see, the USA is the main country where marriage between first cousins is sometimes prohibited or considered incest (only in about half the states).
http://en.wikipedia.org/wiki/Laws_regarding_incest
Hebrew law in the Old Testament did not prohibit marriage between first cousins (although closer relationships were considered incest.)
Roman law prohibited marriage within 4 degrees of consanguinity, which did prohibit marriage between first cousins. This was generally adopted by the Catholic Church. From the ninth century to 1215 the Church extended the ban to 7 degrees of consanguinity.
In 1215, at the Fourth Lateran Council, the Catholic Church reverted to the 4 degrees rule.
The Catholic Church still uses the 4 degrees rule to determine allowable marriages. This law is considered to be 'ecclesiastical law', rather than 'divine law', therefore, it is possible to petition for and receive a 'dispensation' from the church allowing two first cousins to marry. This dispensation has historically been granted on various occasions for royal or noble marriages. Whether the church is inclined to grant such dispensations today, I don't know.