According to the Co-occurrence model, heritable general intelligence, environmental specialized abilities, and somatic modifications co-varied across the Late Modern Era (1800-1999 AD). We report the findings of a model... [ view full abstract ]
According to the Co-occurrence model, heritable general intelligence, environmental specialized abilities, and somatic modifications co-varied across the Late Modern Era (1800-1999 AD). We report the findings of a model testing the prediction of an evolutionary multilevel selection theory that heritable general intelligence is largely group-selected trait. Due to variations increases in group competition as a product of harsher and unpredictable ecologies, this study hypothesized a shift from group selective pressures in the Early Modern Era, to individual selective pressures during the Late Modern Era. Hence, more intense competition between groups led to an increase in heritable general intelligence, whereas a reduction in inter-group competition saw a decrease in population values of heritable general intelligence.This project collected climatic data, as measured as mean global temperatures, between 1600 to 1999 such as 1) Global annual land-surface air temperature anomalies; 2) Global land and sea surface temperature anomalies, and 3) Surface temperature for Central England. To determine the degree of group selection, “Altruism Words” were collected from the Darwin’s (1871) Descent of Man (DMAW). Whereas Google Ngram WordSum HardWords was used as an indicator of heritable general intelligence (a measure validated by other studies). It is worth noting however, since Google Ngram exclusively keeps records of English words, this study used data from Canada, Australia, New Zealand, the United States, and the UK (i.e., Britannic nations). Furthermore, as an indicator of conflict, war fatalities between 1600 to 1999 were collected for each one of aforementioned countries from the Center of Global Economics History. Since population growth is a potential confounding factor at the time of estimating mortality, standardized rates per 100,000 individuals were calculated in accordance to the population size corresponding to each nation on each year. To determine the effect of Britannic world proportion at the time, information was collected from economist Max Roser's demographic data repository. Floating means and standard deviations were used to determine the degree of climatic fluctuations across a 25-years interval. A confirmatory factor analysis supported the presence of a single factor comprised of 10 “Altruism Words”. This factor, along with the Britannic warfare mortality data, and the Britannic world proportion, loaded into a group selection factor. Due to the fact temporal data is thought to cause pseudo-replication, a series of Multi level models were used to control for the effect of time upon group selection and the HardWords factor (i.e., prewhitening). The extracted residuals were used in a sequential canonical cascade model, with the floating means and standard deviations entered as predictors, followed by group selection. The results from this study found that group selection is fostered by colder annual temperatures. Even though, the floating standard deviation had no effect upon the group selection factor, the interaction between the floating mean and the floating standard deviation indicates in colder climates, supports the fact that group selection is potentiated by climatic variability. The HardWords factor was significantly predicted by the group selection factor above and beyond the climatic variables. Indicating that higher verbal intelligence is fostered by group selective pressures. These findings offer strong support for the predictions of our evolutionary multilevel selection model in that heritable general intelligence is largely group-selected trait.
Biological & Psychopharmacology , Measurement and Psychometrics , Evolution
