A co-author of the Heritage Foundation’s controversial immigration study resigned from the think tank on Friday amid a firestorm over his research on the intelligence of immigrants.

“Jason Richwine let us know he’s decided to resign from his position,” a spokesperson for Heritage told The Hill in an email. “He’s no longer employed by Heritage. It is our longstanding policy not to discuss internal personnel matters.”

Richwine provided statistical analysis for the Heritage study released earlier this week that said giving the 11 million immigrants estimated to be in the country illegally a path to citizenship would cost the country $6.3 trillion over their lifetimes.

The report sparked a battle among conservatives, who are split over the Senate proposal.

On Wednesday, the study came into question after the Washington Post revealed Richwine’s 2009 doctoral dissertation, in which he argued that inferior genetics are part of the reason “no one knows whether Hispanics will ever reach IQ parity with whites.”

“The average IQ of immigrants in the United States is substantially lower than that of the white native population, and the difference is likely to persist over several generations,” he wrote.

“The consequences are a lack of socioeconomic assimilation among low-IQ immigrant groups, more underclass behavior, less social trust, and an increase in the proportion of unskilled workers in the American labor market. Selecting high-IQ immigrants would ameliorate these problems in the U.S., while at the same time benefiting smart potential immigrants who lack educational access in their home countries.”

Heritage responded by saying that Robert Rector, not Richwine, was the primary author of its immigration study, and quickly distanced itself from Richwine’s earlier work, saying his previous writings do not reflect the positions of the foundation and that they shouldn’t affect how people view the findings of the immigration study.
The controversy threatened to derail Heritage’s opposition to immigration reform during a week when bipartisan negotiations picked up steam.

Rep. Rubén Hinojosa (D-Texas), the chairman of the Congressional Hispanic Caucus, called the group’s study “ugly racism and xenophobia dressed up in economic hyperbole” after learning of the dissertation.