A researcher famed for his work on the microbiomes of hunter-gatherers has been accused by several women of sexual assault, according to U.S. court documents. Jeff Leach, a resident of Terlingua, Texas, co-founded a major open-source, crowdfunded project on the microbiome and is the co-author of multiple papers on gut microbes, including one in Science. In the publicity resulting from the allegations, other questions have emerged about Leach’s academic qualifications and his behavior in the field.
The sexual assault accusations came to light as a result of a defamation suit Leach filed in September 2019. In July 2019, Katy Schwartz, who worked at the Terlingua tourist lodge that Leach runs, filed a police report alleging that he had sexually assaulted her. Schwartz did not press charges, but asserts in court documents that she wanted her experience documented because she feared Leach could be a danger to others.
In the wake of the lawsuit against Schwartz, three other local women filed affidavits. One alleged that Leach had assaulted her, putting his hand up her shorts “without any warning.” A second alleged that he raped her in a “violent assault” for which “there was no consent.” A third affidavit alleged that Leach sexually assaulted a woman, became violent during an argument, and threatened her with litigation.
Leach and his lawyer, Rae Leifeste, told Science that all the charges are unfounded and are a coordinated attack motivated by jealousy and disagreements over money. In an affidavit and in an email to Science, Leach says any sexual contact was consensual and claims that, after the alleged attacks, all of his accusers were friendly toward him in text messages and in other encounters.
On 6 February, Presiding Judge Stephen Ables ruled in favor of Schwartz’s motion to dismiss the defamation lawsuit, based on “anti-SLAPP” (strategic lawsuits against public participation) laws that protect free speech. Leifeste is preparing an appeal.
Leach has collaborated with researchers at King’s College London (KCL), the University of California, San Diego (UCSD), and Stanford University, among others, to study the bacteria that live in the gut and on the skin. He is known for gathering microbiome samples from hunter-gatherers to explore the idea that their microbiomes are healthier than those of people in industrialized societies.
In 2014, Leach gave himself a fecal transplant from a member of the Hadza group of Tanzania, an event widely covered by the media and billed as an effort to boost his health. A few months earlier, he was profiled in Science.
Media accounts have described Leach as an anthropologist, but he told Science last week that he does not have a Ph.D. On various papers, he lists affiliations with the University of Leicester and the London School of Hygiene & Tropical Medicine. KCL officials say he was a visiting research scholar there from August 2016 until July 2018 but is no longer associated with the university. Leach says he is now pursuing a Ph.D. at the University of York, which officials there confirmed. Leach did not answer queries from Science about whether he has an undergraduate degree.
Some researchers who have worked with Leach distanced themselves from him in comments to Science. In 2012, UCSD microbiome researchers Jack Gilbert and Rob Knight founded the American Gut Project with Leach. The project invites members of the public to submit a skin swab or samples of feces or saliva and pay $99 to have their microbes cataloged. Gilbert says he never met Leach in person, however. “That project is now completely outside of his activities, and is being administered by the Microsetta Initiative at UCSD with Rob Knight,” Gilbert told Science. Knight says he no longer collaborates with Leach, and the project’s website no longer mentions him.
Another project removed Leach’s name from its website last week after its leaders learned of the lawsuit. Until 5 February, the website of the Microbiota Vault, an international project to collect human microbiome samples, said Leach would “work to secure samples” from remote populations in Tanzania and Namibia. Maria Gloria Dominguez-Bello, a microbiome researcher at Rutgers University and a coordinator of the project, told Science she was surprised by the accusations and called the news “very disturbing and sad.”
She does not, however, doubt the quality of the samples and data that Leach collected. She notes they are stored in the labs of Knight and microbiome researcher Justin Sonnenburg at Stanford, both of whom have co-authored papers with Leach. Sonnenburg, who is the corresponding author on three papers with Leach, including one in Science, said he has never met Leach in person and received the samples via Dominguez-Bello; he declined any further comment.
The Science paper reported seasonal variation in the Hadza gut microbes, based on samples Leach collected. “It was neat, it was orderly, and the metadata all checked out: Poop was poop, and skin samples were from skin. And when you analyze the samples, they cluster by season,” says Dominguez-Bello, a co-author. The paper concludes that the gut flora varies because of seasonal shifts in diet.
Some anthropologists who have worked extensively with the Hadza are skeptical of the paper. Alyssa Crittenden, an anthropologist at the University of Nevada, Las Vegas, says the Science paper’s generalizations about seasonal foods are “inconsistent with nearly 60 years of data on Hadza diet.” In a critique posted on bioRxiv in 2018, she and colleagues reported that they couldn’t replicate the paper’s results from the authors’ open source data.
Dominguez-Bello says, “The discussion [of diet] could be all wrong, but that doesn’t invalidate the paper. … [It] is claiming there are seasonal variations, that’s all.”
Crittenden says researchers who work with vulnerable groups such as the Hadza need “training in ethnographic data collection and, ideally, bioethics.” As part of the case, Schwartz’s lawyers submitted an affidavit by a Terlingua man who accompanied Leach to Tanzania in 2014. In it, he states that Leach smoked marijuana with study subjects in exchange for access to samples. In court filings, Leach’s lawyers objected to the affidavit, saying the information it contains is not relevant to the defamation case. Leach wrote on his Human Food Project blog that “the Hadza are big pot smokers (they trade honey and meat for weed with the local Datoga).”
Tanzania’s National Institute of Medical Research ethics board confirmed that it reviewed Leach’s research proposal in 2011 or 2012, but could not say whether he currently has permits to work in the country. A member of the Hadza who is familiar with Leach but requested anonymity told Science that Leach’s “work seems to be popular in the U.S., but my people don’t really understand what it is for.”
Daudi Peterson, co-founder of Dorobo Safaris in Tanzania, who works with the Hadza and has helped facilitate Leach’s research, says Leach hasn’t collected samples from the Hadza for more than a year, in part because he is waiting for permits. Peterson says Leach’s relationships with the Hadza are “very good,” and that Leach visited twice last year to connect with them. “Even today his name comes up,” Peterson says. “He’s fondly nicknamed the Hadza word for shit.”
Epidemiologist Tim Spector of KCL, who went with Leach to Tanzania in 2017, says he saw no ethical issues with Leach’s work. “I don’t think he was doing anything others weren’t doing.”
Leach has had a colorful career. As part of the case, Schwartz’s lawyers cited a 2003 civil case in Texas in which Leach was found to have violated laws against deceptive trade practices. The Texas attorney general alleged that Leach had sold subscriptions to magazines that had stopped publishing and had accepted more than $100,000 in payments for a tour in Egypt that was to feature the actor Omar Sharif, but was never organized. Leach failed to contest the claims and the court found them admitted and proven. Leifeste notes Leach has not admitted wrongdoing in this case and says it is not relevant to the lawsuit. Leach also co-launched a pizza chain and helped mount a search for Amelia Earhart’s plane using a robotic submarine.
Leach says he plans to do his Ph.D. thesis on the Hadza. In 2018, he told a podcast he wanted to study the microbiome of Hadza children from birth, including collecting breast milk samples from mothers.