Bright futures
Genetic evidence for natural selection in humans in the contemporary United States
Jonathan Beauchamp
Proceedings of the National Academy of Sciences, 12 July 2016, Pages 7774–7779
Abstract:
Recent findings from molecular genetics now make it possible to test directly for natural selection by analyzing whether genetic variants associated with various phenotypes have been under selection. I leverage these findings to construct polygenic scores that use individuals’ genotypes to predict their body mass index, educational attainment (EA), glucose concentration, height, schizophrenia, total cholesterol, and (in females) age at menarche. I then examine associations between these scores and fitness to test whether natural selection has been occurring. My study sample includes individuals of European ancestry born between 1931 and 1953 who participated in the Health and Retirement Study, a representative study of the US population. My results imply that natural selection has been slowly favoring lower EA in both females and males, and are suggestive that natural selection may have favored a higher age at menarche in females. For EA, my estimates imply a rate of selection of about −1.5 mo of education per generation (which pales in comparison with the increases in EA observed in contemporary times). Although they cannot be projected over more than one generation, my results provide additional evidence that humans are still evolving — albeit slowly, especially compared with the rapid changes that have occurred over the past few generations due to cultural and environmental factors.
---------------------
Lauren Schmitz & Dalton Conley
NBER Working Paper, July 2016
Abstract:
This study examines whether draft-lottery estimates of the causal effect of Vietnam-era military service on schooling vary by genetic propensity toward educational attainment. To capture the complex genetic architecture that underlies the bio-developmental pathways behavioral traits and evoked environments associated with educational attainment, we construct a polygenic score (PGS) for the Vietnam-era cohort in the Health and Retirement Study (HRS) that aggregates thousands of individual loci across the human genome, weighted by effect sizes derived from a recent genome-wide association study (GWAS) for years of education. Our findings suggest veterans with below average PGSs for educational attainment completed fewer years of schooling than comparable non-veterans with the same PGS, primarily due to fewer years of college education. On the other hand, we do not find any difference in the educational attainment of veterans and non-veterans with above average PGSs. Results show that public policies and exogenous environments may induce heterogeneous treatment effects by genetic disposition.
---------------------
The Bell Curve Revisited: Testing Controversial Hypotheses with Molecular Genetic Data
Dalton Conley & Benjamin Domingue
Sociological Science, July 2016
Abstract:
In 1994, the publication of Herrnstein’s and Murray’s The Bell Curve resulted in a social science maelstrom of responses. In the present study, we argue that Herrnstein’s and Murray’s assertions were made prematurely, on their own terms, given the lack of data available to test the role of genotype in the dynamics of achievement and attainment in U.S. society. Today, however, the scientific community has access to at least one dataset that is nationally representative and has genome-wide molecular markers. We deploy those data from the Health and Retirement Study in order to test the core series of propositions offered by Herrnstein and Murray in 1994. First, we ask whether the effect of genotype is increasing in predictive power across birth cohorts in the middle twentieth century. Second, we ask whether assortative mating on relevant genotypes is increasing across the same time period. Finally, we ask whether educational genotypes are increasingly predictive of fertility (number ever born [NEB]) in tandem with the rising (negative) association of educational outcomes and NEB. The answers to these questions are mostly no; while molecular genetic markers can predict educational attainment, we find little evidence for the proposition that we are becoming increasingly genetically stratified.
---------------------
Evidence of dysgenic fertility in China
Mingrui Wang, John Fuerst & Jianjun Ren
Intelligence, July–August 2016, Pages 15–24
Abstract:
The relationship between fertility, intelligence, and education was examined in China using a large sample sourced from the population-representative China Family Panel Studies (CFPS) dataset. For the 1951–1970 birth cohort, the correlation between fertility and gf was −.10. The strength of recent selection against gf in China substantially increased between the 1960s and the mid-1980s. Later (between 1986 and 2000), the speed of decline in gf due to selection stabilized at about .31 points per decade with a slightly downward trend. The total loss from 1971 to 2000 due to dysgenic fertility is estimated to be .75 points. A negative relationship between educational attainment and fertility was additionally found. Both negative relations were stronger for women.
---------------------
Michael Woodley of Menie et al.
Personality and Individual Differences, November 2016, Pages 90–97
Abstract:
Country-level total fertility rates (TFR) and cognitive ability are negatively correlated, suggesting the existence of a selection pressure that might be reducing global G. Also, the cross-population frequencies of several SNPs have been found to predict cognitive ability between countries. This study applies a cross-cultural sociogenetic approach to explore the role of latent factors among cognitive ability measures and these SNPs in moderating the associations among their indicators and TFR. Using a G factor constructed from five measures of cognitive ability, positive moderation is found on the TFR*ability relationship (ρ = 0.251 N = 60.6 countries). Using a metagene common factor among eight SNPs, positive moderation is also found on the TFR*SNP relationship (ρ = 0.816, N = 18 countries). An inference of polygenic selection for lower G is supported by the findings of two multivector co-moderation analyses. When controlled for one another, Human Development Index and metagene frequency both independently predicted TFR (β = − 0.339, and − 0.678 respectively, N = 18 countries). This indicates a joint impact of intelligent fertility control and life history slowing on the distribution of TFR values. Based on these results, polygenic selection might be reducing heritable G globally by − 0.253 points per decade, highlighting the importance of the Flynn effect as a contributor to global development.