"Gene Flow by Selective Emigration as a Possible Cause for Personality Differences Between Small Islands and Mainland Populations", Ciani & Cialuppi 2011:
"Whether personality differences exist between populations is a controversial question. Even though such differences can be measured, it is still not clear whether they are due to individual phenotypic responses to the environment or whether they have a genetic influence. In a population survey we compared the personality traits of inhabitants of an Italian archipelago (the three Egadi islands; N=622) with those of the closest mainland population (Trapani area; N=106) and we found that personality differences between small populations can be detected. Islanders scored significantly lower on the personality traits of openness to experience and extraversion and higher on conscientiousness. We suggest that these personality trait differences could be an adaptive response to a confined socio-environmental niche, genetically produced by a strong, non-random gene flow in the last 20–25 generations, rather than the flexible response of islanders to environmental variables. To test this hypothesis, we compared subsets of the islander population classified by ancestry, birthplace, immigration and emigration and found that differences in extraversion can be accounted for by gene flow, while openness to experience and conscientiousness can also be accounted for by some gene–environment interactions. We propose a Personality Gene Flow hypothesis suggesting that, in small isolated communities, whenever there is strong, non-random emigration, paired with weak and random immigration, we can expect rapid genetic personality change within the population.
[See also "Some uses of models of quantitative genetic selection in social science", Weight & Harpending 2016 http://journals.cambridge.org/article_S002193201600002X ; "Assortative Mating, Class, and Caste", https://www.dropbox.com/s/yuie5dxmq12pwjf/2015-harpending.pdf ]
In order to assess personality differences between populations, Camperio Ciani et al. (Camperio Ciani, Capiluppi, Veronese, & Sartori, 2007; Camperio Ciani, & Ceccarini, 2002) used a new approach, initially developed to study sexual orientation (Camperio Ciani, Corna, & Capiluppi, 2004), consisting of comparing small isolated populations with a reference population which shares a common historical, linguistic and cultural context. In a population survey conducted in three Italian archipelagos they found significant differences between islander and mainlander personality traits on a Big Five scale (Costa & McCrae, 1992; Goldberg, 1990; McCrae & Costa, 1999) based on the adjectives questionnaire validated for Italian language (Perugini & Di Blas, 2002; Perugini & Leone, 1994; Piconi, 1998). The emerging islander personality profile was characterized by lower extraversion and openness to experience, and more conscientiousness and emotional stability than in the mainland inhabitants: they suggested these personality differences could represent traits which result in better adaptation to the island environment. Immigrants to the islands (who had been resident for at least 20 years) were significantly more extraverted and more open to experience than original islanders, that is they retained a mainlander profile despite long-lasting permanence in the insular environment, which led the authors to suspect the presence of a genetic influence on personality, however, the study could not definitely exclude that behaviours learned during childhood were retained in adulthood. Emigrant islanders were found to be more open to experience and more extraverted than sedentary islanders. Camperio Ciani et al. (2007) suggested gene flow as the possible genetic selection mechanism (Bodmer & Cavalli-Sforza, 1976; Camperio Ciani, Stanyon, Scheffrahn, & Sampurno, 1989), that is the voluntary emigration of fertile individuals who were, in this case, higher in extraversion and openess to experience. The purpose of this study is firstly to assess whether the personality trait differences between islanders and mainlanders reported in Camperio Ciani et al. (2007; Camperio Ciani & Ceccarini, 2002) can be detected in a different archipelago with similar socio-ecological conditions to previously studied islands.
Hence, we try to answer the following three questions:
1. Are there differences in personality traits between islanders and mainlanders?
2. Can these differences be ascribed to stable traits of genetic origin, or are they due to individual flexible adaptation to the environment?
3. Which mechanism could account for the origin of these differences?
We selected the Egadi archipelago, the southernmost set of islands off the coast of western Sicily because it has similar linguistic and socio-ecological conditions to those of the previous study, and we had access to all the relevant historical and geographical details required to test our hypothesis.
The Egadiislands (Favignana, Levanzo and Marettimo and a few other islets) constitute the southernmost Italian archipelago, 15–30 sea miles off the western shore of Sicily where the town of Trapani is situated. The total population in the Egadi archipelago is at present 4394, of which 220 are resident in Levanzo Island, 450 in Marettimo Island and the rest in Favignana Island. Only 50% of those who are listed as resident are actually living on the island, the remaining 50% are listed as being resident but have, in fact, emigrated. These islands fulfil the requisites of the long-lasting isolation required to highlight the hypothesized effect of the adaptive selection for personality traits. Even if the archipelago is now a tourist destination, during the last 400 years these islands have experienced limited immigration, a fact confirmed by surname analysis and by studies of birth, marriage and death registries (Veronese, 2003). This means that for at least 20–25 generations the small village communities did not mix
extensively with the mainland population.
...different populations have controlled the islands, all attracted by the island’s strategic position in the Mediterranean. In the middle ages the archipelago was attacked, raided and invaded by the Normans, the Angioinis, the Sicilians and the Hispanics, so that no permanent population was able to survive. The Tunisian pirate Adir Kadir undertook in 1516 the last significant raid that depleted the whole population of the Egadi. After that last episode, no other large scale invasions occurred and, in the second half of 1500, the Spanish crown and the new owner, the Count Pallavicini, re-founded the Egadi population by forcing about 70 families to move to the archipelago from Liguria (homeland of the Pallavicini) and Sicily and Spain (Gallitto, 2008), giving them housing, permission to cultivate the islands and work in the tuna fish farms (Calleri, 2006). Most of the surnames of these founding families are still present in the island population as indicated in the parish records. Since that time no further significant immigration has occurred (Calleri, 2006; Gallitto, 2008; Veronese, 2003). Given that life on the islands was anything but attractive, the only source of immigration over the last 400 years was prisoners, exiled people (from all over Italy and North Africa) and their jail officers, which were sent to the renowned caved prisons on the two main islands of the archipelago, Favignana and Marettimo.
Emigration, on the other hand, has been very high, over 30% for each generational cohort due to population growth and agricultural overexploitation (Calleri, 2006). Emigration was so high that in 1810 the Florio family, the new owners of the islands, was obliged to transfer three to four new families to work in the tuna fishing farms. Emigration continued due to the hard conditions on the islands. The rocky environment made agriculture extremely hard and tuna fishing began to decline as a result of the competition of other developing Mediterranean countries (Gallitto, 2008).
The historical accounts show that the population seldom exceeded 2000 inhabitants in the whole archipelago. In the last 400 years, fecundity, as documented in parish records, averaged between 5 and 7 children per woman, and infant mortality has never exceeded typical rates for Southern Italy (Calleri, 2006). The infant mortality rate averaged between 20% and 30% from the 16th to the 19th century, then progressively decreased to 1% in 1952 and 0.4% in 2009 (Italian National Statistic Institute: ISTAT, 2009). Despite high fecundity and relatively low mortality, the population did not grow because there was a continuous outflow of emigrants, which in the past century averaged about 35% of each generation.
Islanders (n = 528) differ from mainlanders (n = 106) on extraversion and openness to experience after controlling for the effect of the covariates (Figure 3): islanders were significantly less extraverted and less open to experience (À8.3 and À6.0 corrected T-scores, 2 respectively). The other differences were not significant (Table 2). A further comparison between mainlanders and the subset of native islanders with ancient origin ancestry (n = 380) shows a highly significant difference for extraversion ( p < .001), openness to experience ( p < .001) (À9.8 and À6.6 corrected T-scores, respectively), and a significant difference for conscientiousness ( p = .042). While for emotional stability the difference was on the critical level ( p = .051) (Table 2)
Figure 2. Big Five personality traits measured in the sample subsets, expressed in T-scores. T-scores are standardized scores with mean = 50 and standard deviation = 10, computed by standardizing the raw scores with reference to the mainland control sample
[note that 't' here does not refer to the z/t-statistic in two-sample tests of statistical-significance]
We have additional evidence against the alternative hypothesis suggested by Van Oers (2007) that the personality of the founding populations of the islands previously studied was different from the mainlanders right from the beginning, as per the founder effect (Fisher, 1930). Already Camperio Ciani et al. (2007) observed the same pattern of personality differences in three different archipelagos, and in this study we again observed almost exactly the same pattern of differences in another one, with a rather different historical background. We here show in a comparative table (Table 4) between this study and the previous one that except minor difference in effect size Extraversion, and Openness to experience show always the same pattern of differences, conscentiousness has only a minor difference when comparing emigrants and sedentary islanders, and the other two traits never show any significant differences. Hence, at present, after about 25 generations, we have observed four independent archipelagos (including the ones considered in the previous study), composed of 15 inhabited islands in total, showing a convergent personality pattern (Table 4). It is unlikely that this is the result of multiple and similar founder effects."
Fun.
"Whether personality differences exist between populations is a controversial question. Even though such differences can be measured, it is still not clear whether they are due to individual phenotypic responses to the environment or whether they have a genetic influence. In a population survey we compared the personality traits of inhabitants of an Italian archipelago (the three Egadi islands; N=622) with those of the closest mainland population (Trapani area; N=106) and we found that personality differences between small populations can be detected. Islanders scored significantly lower on the personality traits of openness to experience and extraversion and higher on conscientiousness. We suggest that these personality trait differences could be an adaptive response to a confined socio-environmental niche, genetically produced by a strong, non-random gene flow in the last 20–25 generations, rather than the flexible response of islanders to environmental variables. To test this hypothesis, we compared subsets of the islander population classified by ancestry, birthplace, immigration and emigration and found that differences in extraversion can be accounted for by gene flow, while openness to experience and conscientiousness can also be accounted for by some gene–environment interactions. We propose a Personality Gene Flow hypothesis suggesting that, in small isolated communities, whenever there is strong, non-random emigration, paired with weak and random immigration, we can expect rapid genetic personality change within the population.
[See also "Some uses of models of quantitative genetic selection in social science", Weight & Harpending 2016 http://journals.cambridge.org/article_S002193201600002X ; "Assortative Mating, Class, and Caste", https://www.dropbox.com/s/yuie5dxmq12pwjf/2015-harpending.pdf ]
In order to assess personality differences between populations, Camperio Ciani et al. (Camperio Ciani, Capiluppi, Veronese, & Sartori, 2007; Camperio Ciani, & Ceccarini, 2002) used a new approach, initially developed to study sexual orientation (Camperio Ciani, Corna, & Capiluppi, 2004), consisting of comparing small isolated populations with a reference population which shares a common historical, linguistic and cultural context. In a population survey conducted in three Italian archipelagos they found significant differences between islander and mainlander personality traits on a Big Five scale (Costa & McCrae, 1992; Goldberg, 1990; McCrae & Costa, 1999) based on the adjectives questionnaire validated for Italian language (Perugini & Di Blas, 2002; Perugini & Leone, 1994; Piconi, 1998). The emerging islander personality profile was characterized by lower extraversion and openness to experience, and more conscientiousness and emotional stability than in the mainland inhabitants: they suggested these personality differences could represent traits which result in better adaptation to the island environment. Immigrants to the islands (who had been resident for at least 20 years) were significantly more extraverted and more open to experience than original islanders, that is they retained a mainlander profile despite long-lasting permanence in the insular environment, which led the authors to suspect the presence of a genetic influence on personality, however, the study could not definitely exclude that behaviours learned during childhood were retained in adulthood. Emigrant islanders were found to be more open to experience and more extraverted than sedentary islanders. Camperio Ciani et al. (2007) suggested gene flow as the possible genetic selection mechanism (Bodmer & Cavalli-Sforza, 1976; Camperio Ciani, Stanyon, Scheffrahn, & Sampurno, 1989), that is the voluntary emigration of fertile individuals who were, in this case, higher in extraversion and openess to experience. The purpose of this study is firstly to assess whether the personality trait differences between islanders and mainlanders reported in Camperio Ciani et al. (2007; Camperio Ciani & Ceccarini, 2002) can be detected in a different archipelago with similar socio-ecological conditions to previously studied islands.
Hence, we try to answer the following three questions:
1. Are there differences in personality traits between islanders and mainlanders?
2. Can these differences be ascribed to stable traits of genetic origin, or are they due to individual flexible adaptation to the environment?
3. Which mechanism could account for the origin of these differences?
We selected the Egadi archipelago, the southernmost set of islands off the coast of western Sicily because it has similar linguistic and socio-ecological conditions to those of the previous study, and we had access to all the relevant historical and geographical details required to test our hypothesis.
The Egadiislands (Favignana, Levanzo and Marettimo and a few other islets) constitute the southernmost Italian archipelago, 15–30 sea miles off the western shore of Sicily where the town of Trapani is situated. The total population in the Egadi archipelago is at present 4394, of which 220 are resident in Levanzo Island, 450 in Marettimo Island and the rest in Favignana Island. Only 50% of those who are listed as resident are actually living on the island, the remaining 50% are listed as being resident but have, in fact, emigrated. These islands fulfil the requisites of the long-lasting isolation required to highlight the hypothesized effect of the adaptive selection for personality traits. Even if the archipelago is now a tourist destination, during the last 400 years these islands have experienced limited immigration, a fact confirmed by surname analysis and by studies of birth, marriage and death registries (Veronese, 2003). This means that for at least 20–25 generations the small village communities did not mix
extensively with the mainland population.
...different populations have controlled the islands, all attracted by the island’s strategic position in the Mediterranean. In the middle ages the archipelago was attacked, raided and invaded by the Normans, the Angioinis, the Sicilians and the Hispanics, so that no permanent population was able to survive. The Tunisian pirate Adir Kadir undertook in 1516 the last significant raid that depleted the whole population of the Egadi. After that last episode, no other large scale invasions occurred and, in the second half of 1500, the Spanish crown and the new owner, the Count Pallavicini, re-founded the Egadi population by forcing about 70 families to move to the archipelago from Liguria (homeland of the Pallavicini) and Sicily and Spain (Gallitto, 2008), giving them housing, permission to cultivate the islands and work in the tuna fish farms (Calleri, 2006). Most of the surnames of these founding families are still present in the island population as indicated in the parish records. Since that time no further significant immigration has occurred (Calleri, 2006; Gallitto, 2008; Veronese, 2003). Given that life on the islands was anything but attractive, the only source of immigration over the last 400 years was prisoners, exiled people (from all over Italy and North Africa) and their jail officers, which were sent to the renowned caved prisons on the two main islands of the archipelago, Favignana and Marettimo.
Emigration, on the other hand, has been very high, over 30% for each generational cohort due to population growth and agricultural overexploitation (Calleri, 2006). Emigration was so high that in 1810 the Florio family, the new owners of the islands, was obliged to transfer three to four new families to work in the tuna fishing farms. Emigration continued due to the hard conditions on the islands. The rocky environment made agriculture extremely hard and tuna fishing began to decline as a result of the competition of other developing Mediterranean countries (Gallitto, 2008).
The historical accounts show that the population seldom exceeded 2000 inhabitants in the whole archipelago. In the last 400 years, fecundity, as documented in parish records, averaged between 5 and 7 children per woman, and infant mortality has never exceeded typical rates for Southern Italy (Calleri, 2006). The infant mortality rate averaged between 20% and 30% from the 16th to the 19th century, then progressively decreased to 1% in 1952 and 0.4% in 2009 (Italian National Statistic Institute: ISTAT, 2009). Despite high fecundity and relatively low mortality, the population did not grow because there was a continuous outflow of emigrants, which in the past century averaged about 35% of each generation.
Islanders (n = 528) differ from mainlanders (n = 106) on extraversion and openness to experience after controlling for the effect of the covariates (Figure 3): islanders were significantly less extraverted and less open to experience (À8.3 and À6.0 corrected T-scores, 2 respectively). The other differences were not significant (Table 2). A further comparison between mainlanders and the subset of native islanders with ancient origin ancestry (n = 380) shows a highly significant difference for extraversion ( p < .001), openness to experience ( p < .001) (À9.8 and À6.6 corrected T-scores, respectively), and a significant difference for conscientiousness ( p = .042). While for emotional stability the difference was on the critical level ( p = .051) (Table 2)
Figure 2. Big Five personality traits measured in the sample subsets, expressed in T-scores. T-scores are standardized scores with mean = 50 and standard deviation = 10, computed by standardizing the raw scores with reference to the mainland control sample
[note that 't' here does not refer to the z/t-statistic in two-sample tests of statistical-significance]
We have additional evidence against the alternative hypothesis suggested by Van Oers (2007) that the personality of the founding populations of the islands previously studied was different from the mainlanders right from the beginning, as per the founder effect (Fisher, 1930). Already Camperio Ciani et al. (2007) observed the same pattern of personality differences in three different archipelagos, and in this study we again observed almost exactly the same pattern of differences in another one, with a rather different historical background. We here show in a comparative table (Table 4) between this study and the previous one that except minor difference in effect size Extraversion, and Openness to experience show always the same pattern of differences, conscentiousness has only a minor difference when comparing emigrants and sedentary islanders, and the other two traits never show any significant differences. Hence, at present, after about 25 generations, we have observed four independent archipelagos (including the ones considered in the previous study), composed of 15 inhabited islands in total, showing a convergent personality pattern (Table 4). It is unlikely that this is the result of multiple and similar founder effects."
Fun.
