February 1, 2013
A study by two economists that used genetic diversity as a proxy for ethnic and cultural diversity has drawn fierce rebuttals from anthropologists and geneticists.
By Paul Voosen
Oded Galor and Quamrul Ashraf once thought their research into the causes of societal wealth would be seen as a celebration of diversity. However it has been described, though, it has certainly not been celebrated. Instead, it has sparked a dispute among scholars in several disciplines, many of whom are dubious of any work linking societal behavior to genetics. In the latest installment of the debate, 18 Harvard University scientists have called their work “seriously flawed on both factual and methodological grounds.”
Mr. Galor and Mr. Ashraf, economists at Brown University and Williams College, respectively, have long been fascinated by the historical roots of poverty. Six years ago, they began to wonder if a society’s diversity, in any way, could explain its wealth. They probed tracts of interdisciplinary data and decided they could use records of genetic diversity as a proxy for ethnic and cultural diversity. And after doing so, they found that, yes, a bit of genetic diversity did seem to help a society’s economic growth.
Since last fall, when the pair’s work began to filter out into the broader scientific world, their study has exposed deep rifts in how economists, anthropologists, and geneticists talk—and think. It has provoked calls for caution in how economists use genetic data, and calls of persecution in response. And all of this happened before the study was finally published, in the American Economic Review this month.
“Through this analysis, we’re getting a better understanding of how the world operates in order to alleviate poverty,” Mr. Ashraf said. Any other characterization, he added, is a “gross misunderstanding.”
A barrage of criticism has been aimed at the study since last fall by a team of anthropologists and geneticists at Harvard. The critique began with a short, stern letter, followed by a rejoinder from the economists; now an expanded version of the Harvard critique will appear in February inCurrent Anthropology.
Fundamentally, the dispute comes down to issues of data selection and statistical power. The paper is a case of “garbage in, garbage out,” the Harvard group says. The indicators of genetic diversity that the economists use stem from only four or five independent points. All the regression analysis in the world can’t change that, said Nick Patterson, a computational biologist at Harvard and MIT’s Broad Institute.
“The data just won’t stand for what you’re claiming,” Mr. Patterson said. “Technical statistical analysis can only do so much for you. … I will bet you that they can’t find a single geneticist in the world who will tell them what they did was right.”
In some respects, the study has become an exemplar for how the nascent field of “genoeconomics,” a discipline that seeks to twin the power of gene sequencing and economics, can go awry. Connections between behavior and genetics rightly need to clear high bars of evidence, said Daniel Benjamin, an economist at Cornell University and a leader in the field who has frequently called for improved rigor.
“It’s an area that’s fraught with an unfortunate history and ethical quagmires,” he said. Mr. Galor and Mr. Ashraf had a creative idea, he added, even if all their analysis doesn’t pass muster.
“I’d like to see more data before I’m convinced that their [theory] is true,” said Mr. Benjamin, who was not affiliated with the study or the critique. The Harvard critics make all sorts of complaints, many of which are valid, he said. “But fundamentally the issue is that there’s just not that much independent data.”
Claims of ‘Outsiders’
The dispute also exposes issues inside anthropology, added Carl Lipo, an anthropologist at California State University at Long Beach who is known for his study of Easter Island. “Anthropologists have long tried to walk the line whereby we argue that there are biological origins to much of what makes us human, without putting much weight that any particular attribute has its origins in genetics [or] biology,” he said.
The debate often erupts in lower-profile ways and ends with a flurry of anthropologists’ putting down claims by “outsiders,” Mr. Lipo said. (Mr. Ashraf and Mr. Galor are “out on a limb” with their conclusions, he added.) The angry reaction speaks to the limits of anthropology, which has been unable to delineate how genetics reaches up through the idiosyncratic circumstances of culture and history to influence human behavior, he said.
Certainly, that reaction has been painful for the newest pair of outsiders.
Mr. Galor is well known for studying the connections between history and economic development. And like much scientific work, his recent research began in reaction to claims made by Jared Diamond, the famed geographer at the University of California at Los Angeles, that the development of agriculture gave some societies a head start. What other factors could help explain that distribution of wealth? Mr. Galor wondered.
Since records of ethnic or cultural diversity do not exist for the distant past, they chose to use genetic diversity as a proxy. (There is little evidence that it can, or can’t, serve as such a proxy, however.) Teasing out the connection to economics was difficult—diversity could follow growth, or vice versa—but they gave it a shot, Mr. Galor said.
“We had to find some root causes of the [economic] diversity we see across the globe,” he said.
They were acquainted with the “Out of Africa” hypothesis, which explains how modern human beings migrated from Africa in several waves to Asia and, eventually, the Americas. Due to simple genetic laws, those serial waves meant that people in Africa have a higher genetic diversity than those in the Americas. It’s an idea that found support in genetic sequencing of native populations, if only at the continental scale.
Combining the genetics with population-density estimates—data the Harvard group says are outdated—along with deep statistical analysis, the economists found that the low and high diversity found among Native Americans and Africans, respectively, was detrimental to development. Meanwhile, they found a sweet spot of diversity in Europe and Asia. And they stated the link in sometimes strong, causal language, prompting another bitter discussion with the Harvard group over correlation and causation.
An ‘Artifact’ of the Data?
The list of flaws found by the Harvard group is long, but it boils down to the fact that no one has ever made a solid connection between genes and poverty before, even if genetics are used only as a proxy, said Jade d’Alpoim Guedes, a graduate student in anthropology at Harvard and the critique’s lead author.
“If my research comes up with findings that change everything we know,” Ms. d’Alpoim Guedes said, “I’d really check all of my input sources. … Can I honestly say that this pattern that I see is true and not an artifact of the input data?”
Mr. Ashraf and Mr. Galor found the response to their study, which they had previewed many times over the years to other economists, to be puzzling and emotionally charged. Their critics refused to engage, they said. They would have loved to present their work to a lecture hall full of anthropologists at Harvard. (Mr. Ashraf, who’s married to an anthropologist, is a visiting scholar this year at Harvard’s Kennedy School.) Their gestures were spurned, they said.
“We really felt like it was an inquisition,” Mr. Galor said. “The tone and level of these arguments were really so unscientific.”
Mr. Patterson, the computational biologist, doesn’t quite agree. The conflict has many roots but derives in large part from differing standards for publication. Submit the same paper to a leading genetics journal, he said, and it would not have even reached review.
“They’d laugh at you,” Mr. Patterson said. “This doesn’t even remotely meet the cut.”
In the end, it’s unfortunate the economists chose genetic diversity as their proxy for ethnic diversity, added Mr. Benjamin, the Cornell economist. They’re trying to get at an interesting point. “The genetics is really secondary, and not really that important,” he said. “It’s just something that they’re using as a measure of the amount of ethnic diversity.”
Mr. Benjamin also wishes they had used more care in their language and presentation.
“It’s not enough to be careful in the way we use genetic data,” he said. “We need to bend over backwards being careful in the way we talk about what the data means; how we interpret findings that relate to genetic data; and how we communicate those findings to readers and the public.”
Mr. Ashraf and Mr. Galor have not decided whether to respond to the Harvard critique. They say they can, point by point, but that ultimately, the American Economic Review’s decision to publish the paper as its lead study validates their work. They want to push forward on their research. They’ve just released a draft study that probes deeper into the connections between genetic diversity and cultural fragmentation, Mr. Ashraf said.
“There is much more to learn from this data,” he said. “It is certainly not the final word.”