By Rose Schapiro, AB'09

Photography by iStockphoto

Genetic migration

Ecological pressures like climate, diet, and disease don’t tell the whole story of human genetic adaptation over the past 100,000 years. In a study published online in the June 5 PLoS Genetics, geneticist Jonathan Pritchard, human-genetics PhD student Joseph Pickrell, and researchers from Stanford and the University of California, Davis, found that population history also affects DNA variation. Growth and contraction rates for individual groups and migrations between them helped keep human populations from diverging more strongly as they ranged to disparate habitats across the globe. Scientists had previously attributed most recent evolutionary changes to environmentally driven natural selection. By analyzing data from two major data sets, HapMap and the Human Genome Diversity Project, Pritchard and his coauthors found that population movements also powerfully influenced genetic variation patterns.

Photo: Young Finch
Arranged marriages are not the “traditional” Bengali practice they’re assumed to be.

Colonial India’s marriage market

In Marriage and Modernity (Duke University Press, 2009), South Asian languages & civilizations assistant professor Rochona Majumdar, PhD’03, argues that arranged marriages in Bengal are not a “traditional” practice from Indian antiquity—as is often assumed—but a product of India’s colonial era. Using matrimonial newspaper advertisements, wedding invitations, legal debates, photographs, and other cultural artifacts, Majumdar writes that although “arranged marriages were not novel to the late 19th century,” they were transformed and standardized by an emerging marriage market influenced by urbanization, print media, family-property–rights reforms, and Western education. The end result led not to nuclear families as it did in the West, but to “the valorization of a particular idea of the joint family, a structure with an older male or female head and usually three or more generations living together.”

Cancer is depressing

Many cancer patients suffer depression, and it may be more than simply a psychological reaction; biology may also play a role. Researchers at the University’s Institute for Mind and Biology found that tumors in rats elevated their brains’ levels of proinflammatory cytokines, proteins known to induce depression symptoms. The rats started showing mood changes before any overt signs of illness. Published in the May 18 Proceedings of the National Academy of Sciences, the study was led by behavioral-neuroscience postdoc Leah M. Pyter and coauthored by institute researchers Martha K. McClintock, Brian J. Prendergast, Vanessa Pineros, AB’08, and Jerome A. Galang, AB’05. Their research is the first to suggest that depression may stem from the cancer itself.

Reconsidering Hawthorne

The Hawthorne effect asserts that simply knowing they’re part of an experiment prompts study subjects to improve their behavior. The principle has held sway since the 1920s, when a pair of engineers looking for the optimum shop-floor lighting for worker productivity began raising and lowering the lights at the Hawthorne Works factory in Cicero, Illinois. The engineers found that workers sped up every time factory illumination altered—whether the lights grew brighter or dimmer. In a May National Bureau of Economic Research working paper, economists Steven Levitt and John List argue that the worker-productivity changes may in fact have been a fluke. Unearthing the original data, long thought lost, Levitt and List note that the lighting always changed when the factory closed on Sunday, and worker productivity rose at the start of every work week, regardless of whether experiments were under way. The slowdown that coincided with the experiments’ termination at the start of summer may have been caused by hot weather, which usually decreases productivity.

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