More genetic diversity does not lead to higher levels of economic development, according to research conducted by Oded Galor, professor of economics. Through the study of the relationship between genetic diversity and economic output, Galor and fellow researchers showed that the effect on developmental outcomes is "hump-shaped," meaning that societies falling near the middle of the genetic diversity spectrum tend to exhibit the highest levels of growth.
Galor developed and gathered support for his hypothesis about the effect of genetic diversity with former graduate student Quamrul Ashraf MA'04 PhD'09, who is now a Williams College professor. Galor is known as the father of Unified Growth Theory, which examines human economic growth over the past 10,000 years.
America falls near the middle of the genetic diversity distribution - the top of the hump - with African countries being the most diverse and Latin American ones being the least diverse.
The basic reasoning behind the hump-shaped model is that though genetic diversity is important for specialization and innovation, too much diversity has historically led to social instability and a dearth of collaboration.
"Diversity stimulates technological innovation critical for growth, but more diverse countries also have more civil wars," Galor said. The idea that homogenous societies work more collaboratively is supported by evolutionary biology, he added.
A forthcoming paper by Galor and Ashraf - entitled "The 'Out of Africa' Hypothesis, Human Genetic Diversity and Comparative Economic Development" - was selected by the editors of the journal Science as a "highlight of recent literature" across all disciplines in the Sept. 7 issue.
Galor's research was funded by the National Science Foundation, which is relatively rare for economics research and may also speak to the interdisciplinary nature of the work, Galor said.
For Galor, research that cuts across disciplinary boundaries is perfectly natural. Though he recognizes the modern academic system is designed to create specialists, he said it is important for modern intellectuals to remain informed about all fields. He regularly reads Science and Nature and has "always been intrigued by human evolution and its relationship with economic development," he said.
This paper focuses on the phenomenon that genetic homogeneity increases with distance from where man first evolved.
South America, whose indigenous population is the most homogenous in the world, was settled only by the very small subset of early man who decided to cross the land bridge to Alaska and then walk down through the entirety of North America.
The theory that the overland distance from Addis Ababa, a location reasonably close to where humans evolved, to a population's ancestral home is a good estimate of genetic homogeneity is verified by genetic testing. This methodology for determining genetic diversity allowed Galor and Ashraf to expand their sample to nearly every country and ethnic population in the world.
To account for immigration in modern nations, the researchers analyzed the diversity of a nation's ethnicities and then factored in how genetically diverse the ethnicities were from each other.
Galor said the data was "strikingly consistent" with what he expected, adding that this is the exception to the norm in research.
Galor and his colleagues subjected the theory to two to three years' worth of tests, and "every test confirmed the hypothesis." The model held up in three different historical time periods over the past two millennia. For the historical dates, Galor and Ashraf used population density instead of Gross Domestic Product per capita to measure economic development. As technology has increased in importance over time, optimum genetic diversity has become increasingly heterogeneous - consistent with Galor's theory.
The hypothesis also holds when the sample is limited to countries with 97 percent indigenous populations, suggesting that genetic effects on growth are independent from immigration.
Examining the endpoints of the modern data also illustrates the theory's power. According to Galor and Ashraf's model, a 1 percent increase in Bolivia's genetic diversity would lead to a 41 percent increase in per capita income, while a 1 percent decrease in Ethiopia's genetic diversity would lead to a 21 percent increase in income. In comparison, a 1 percent increase or decrease in the diversity of the United States would decrease income by about 2 percent.
Going forward, Galor mentioned a similar methodology could be used to analyzed countries' Olympic performances, where he hypothesized "genetically heterogeneous countries should be better at individual sports, while genetically homogenous countries should be better at team sports."
He also plans to examine how genetics might have played a role in the "reversal of fortune," where after the colonial period, North America became more developed than South America. Galor intends to show that - contrary to mainstream academic thought - genetics, not governmental institutions, played the most important role in this reversal.
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