In some remote villages in Euope, cut off from the worlds for 6 months every year due to winter weather, incest before the 1950's was rampant.
People lived in small hovels and often all the family slept in one room.
The evidence and results of such practices are obvious, even still today. Poor health and low intelligence show that incest cannot generally produce a healthy community. As an aside, as it was happening in Germany as well, in the early 30's, it was decided after 1933 to have detachments of the army training in those areas and the were billeted with local families.
"jus primae noctae" was still practised in parts till the early 30's.
Laws were introduced to sterilise offspring from incestuous relationships as well as persons who committed incest and other taboo offences (including homosexuality).
