Marrying to Sapinda that is a common body ancestor from both mother and father sides are prohibited to a certain limits to avoid incest and other bodily harms in next generations due to such marriages.
Marrying within a family can lead to abnormalities in your future offspring. … When two people having the same genes marry and reproduce, these once dormant recessive (ineffective) genes double, making them more likely to cause genetic abnormalities in children.
This was the wisdom of our ancient texts supported by modern science and modern Hindu Law too.
https://www.theguardian.com/science/2013/jul/04/marriage-first-cousins-birth-defects
Original Article: here
