The relationship between inbreeding, migration and population density in Norway

Area of Science:

• Human genetics
• Population studies
• Sociology

Background:

• Inbreeding levels and the proportion of non-migrants (residents in their municipality of birth) were investigated in rural Norwegian districts.
• Previous research suggests a link between population characteristics and genetic diversity.

Purpose of the Study:

• To examine the relationship between inbreeding levels and the proportion of non-migrants in Norwegian rural districts.
• To analyze the correlation between inbreeding and population density.
• To compare inbreeding ratios across different types of municipalities (rural, industrial, urban).

Main Methods:

• Analysis of consanguineous marriage data (first- and second-cousin marriages).
• Calculation of the proportion of non-migrants within municipalities.
• Statistical correlation analysis between inbreeding, non-migrant proportion, and population density.
• Comparison of inbreeding ratios across diverse settlement types.

Main Results:

• A clear upward trend in consanguineous marriages was observed with increasing proportions of non-migrants, rising from 0.39% to 4.3%.
• A significant negative correlation (rs=-0.86) was found between inbreeding and population density.
• Maximum inbreeding occurred in sparsely populated areas with a high proportion of non-migrants.
• High ratios of second- to first-cousin marriages were noted in rural, industrial, and small towns, while larger towns showed the lowest inbreeding and ratio.

Conclusions:

• In rural Norway, a higher proportion of non-migrants is strongly associated with increased levels of inbreeding.
• Population density is a significant factor influencing inbreeding rates, with lower density correlating with higher inbreeding.
• Settlement type influences inbreeding patterns, with rural and industrial areas exhibiting higher consanguinity than larger urban centers.