Some Migration-Related Studies

I have too many tabs open on my computer, so here are some studies/writings which all touch on migration/population movements in some way:

Biographical Memoirs of Henry Harpending [pdf]:

The late Henry Harpending of West Hunter blog, along with Greg Cochran, wrote the 10,000 Year Explosion, did anthropological field work among the Ju/’hoansi, and pioneered population genetics. The biography has many interesting parts:

Henry’s early research on population genetics also helped establish the close relationship between genetics and geography. Genetic differences between groups tend to mirror the geographic distance between them, so that a map of genetic distances looks like a geographic map (Harpending and Jenkins, 1973). Henry developed methods for studying this relationship that are still in use. …

Meanwhile, Henry’s Kalahari field experience also motivated an interest in population ecology. Humans cope with variation in resource supply either by storage (averaging over time) or by mobility and sharing (averaging over space). These strategies are mutually exclusive. Those who store must defend their stored resources against others who would like to share them. Conversely, an ethic of sharing makes storage impossible. The contrast between the mobile and the sedentary Ju/’hoansi in Henry’s sample therefore represented a fundamental shift in strategy. …

Diseases need time to cause lesions on bone. If the infected individual dies quickly, no lesion will form, and the skeleton will look healthy. Lesions form only if the infected individual is healthy enough to survive for an extended period. Lesions on ancient bone may therefore imply that the population was healthy! …

In the 1970s, as Henry’s interest in genetic data waned, he began developing population genetic models of social evolution. He overturned 40 years of conventional wisdom by showing that group selection works best not when groups are isolated but when they are strongly connected by gene flow (1980, pp. 58-59; Harpending and Rogers, 1987). When gene flow is restricted, successful mutants cannot spread beyond the initial group, and group selection stalls.

Genetic Consequences of Social Stratification in Great Britain:

Human DNA varies across geographic regions, with most variation observed so far reflecting distant ancestry differences. Here, we investigate the geographic clustering of genetic variants that influence complex traits and disease risk in a sample of ~450,000 individuals from Great Britain. Out of 30 traits analyzed, 16 show significant geographic clustering at the genetic level after controlling for ancestry, likely reflecting recent migration driven by socio-economic status (SES). Alleles associated with educational attainment (EA) show most clustering, with EA-decreasing alleles clustering in lower SES areas such as coal mining areas. Individuals that leave coal mining areas carry more EA-increasing alleles on average than the rest of Great Britain. In addition, we leveraged the geographic clustering of complex trait variation to further disentangle regional differences in socio-economic and cultural outcomes through genome-wide association studies on publicly available regional measures, namely coal mining, religiousness, 1970/2015 general election outcomes, and Brexit referendum results.

Let’s hope no one reports on this as “They found the Brexit gene!”

Can you Move to Opportunity? Evidence from the Great Migration [PDF]:

The northern United States long served as a land of opportunity for black Americans, but today the region’s racial gap in intergenerational mobility rivals that of the South. I show that racial composition changes during the peak of the Great
Migration (1940-1970) reduced upward mobility in northern cities in the long run,
with the largest effects on black men. I identify urban black population increases
during the Migration at the commuting zone level using a shift-share instrument,
interacting pre-1940 black southern migrant location choices with predicted outmigration from southern counties. The Migration’s negative effects on children’s
adult outcomes appear driven by neighborhood factors, not changes in the characteristics of the average child. As early as the 1960s, the Migration led to greater white enrollment in private schools, increased spending on policing, and higher crime and incarceration rates. I estimate that the overall change in childhood environment induced by the Great Migration explains 43% of the upward mobility gap between black and white men in the region today.

43% is huge and, IMO, too big. However, the author may be on to something.

Lineage Specific Histories of Mycobacterium Tuberculosis Dispersal in Africa and Eurasia:

Mycobacterium tuberculosis (M.tb) is a globally distributed, obligate pathogen of humans that can be divided into seven clearly defined lineages. … We reconstructed M.tb migration in Africa and Eurasia, and investigated lineage specific patterns of spread. Applying evolutionary rates inferred with ancient M.tb genome calibration, we link M.tb dispersal to historical phenomena that altered patterns of connectivity throughout Africa and Eurasia: trans-Indian Ocean trade in spices and other goods, the Silk Road and its predecessors, the expansion of the Roman Empire and the European Age of Exploration. We find that Eastern Africa and Southeast Asia have been critical in the dispersal of M.tb.

I spend a surprising amount of time reading about mycobacteria.

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