Do birds of a feather flock together? Factors for religious heterogamy

Abstract

Social cohesion – particularly with regard to the integration of migrants – is primarily measured in terms of education, labour market participation, unemployment, income levels and poverty. When seen from a historical long-term perspective (considering the migrations of Homo sapiens in the past 300,000 years) admixture merged members of diverse groups and forged – in addition to social ties – ‘strong biological ties’ of kinship, proposing that religious heterogamy is a long-term layer of social cohesion. Accordingly, this study investigated, on the basis of more than 600,000 men and women aged 26–35 years from Austria 2001, Germany (West) 1987, Ireland 2011, Portugal 2011, Romania 2011 and Switzerland 2000, which demographic characteristics foster religious heterogamy, controlling for various confounding factors using linear mixed modelling. By far the most important factor explaining religious heterogamy was the share of adherents to an individual’s religious group in their area of residence. It can be concluded that the rate of intermarriage declines with the increasing size of an individual’s religious group in their area of residence. From a long-term perspective the lack of familial ties (and conjoint offspring) between religious groups could lead to a lack of social cohesion.

Marriage in the Melting Pot: An Evolutionary Approach to European Ancestry, Homogamy, and Fertility in the United States

“…If more individuals of their own ancestry are at hand for marriage, individuals tend to marry homogamous, a pattern that was previously reported by Thomas (1951) and Blau et al (1982). Recently, we have also found comparable marriage patterns on the basis of religious denominations in Europe (Fieder et al, 2020).…”

“…These two divergent trends pose a dilemma: on the one side, the existing preference for homogamy, which at times has a fitness benefit (e.g., in the case of religious homogamy), and on the other side, the effects of genetic bonds ensuring the highest levels of cooperation within diverse social groups. Evidence suggests that the availability of mates within the area of residence is a decisive factor (out marriage decreases with the number of available mates of the in-group), a finding which we have also documented for religiously heterogamous marriages in Europe ( Fieder et al, 2020 ). Therefore, as migration and admixture are continuous behavioral traits of the human species (reviewed in Reich, 2018 ), the dispersal of diverse populations in geographic areas will prove to be an important indicator for intermarriage rates and therefore potentially long-term social cohesion.…”

“…Understanding these processes may help to comprehend long-term social cohesion in the context of migration. From the perspective of kin selection ( Hamilton, 1964 ), we argued that long-term social cohesion between groups of different cultural, ethnic, and religious origins is ensured if genetic bonds transcend group divisions ( Fieder et al, 2020 ). At the same time, we are aware that humans have a strong tendency toward homogamy, which has been demonstrated by several factors, e.g., body height ( Stulp et al, 2013 , 2017 ), religion (reviewed in Fieder and Huber, 2016 ), political attitudes, and ethnicity ( Blackwell and Lichter, 2004 ; Fu and Heaton, 2008 ).…”

“…Data from the census of 1980 were used for the analysis as only this census covered all the variables needed for a stringent investigation. Based on previous studies, we assume that the share of individuals from a certain ancestry in a geographical region, education, and income influences the willingness to marry heterogamous ( Blau et al, 1982 ; Fieder et al, 2020 ) and if assortative mating is occurring by the chance or not. Furthermore, findings suggest ( Huber and Fieder, 2011 , 2016 , 2018 ; Fieder and Huber, 2016 ) that in homogamous relationships, the number of children is increasing and childlessness is decreasing, leading to fitness benefits.…”

Marriage in the Melting Pot: An evolutionary approach to European ancestry, homogamy and fertility in the United States

“…recently, we have also found comparable marriage patterns on the basis of religious denominations in Europe (Fieder et al 2019).…”