MikeLigalig.com

Why Do Monkeys Get Fat?
CAS biological anthropologist on primates, genes, and obesity
10.25.2016
By Barbara Moran


A vervet monkey. “They’re very clever. They’re very social,” says Christopher Schmitt. “Research on vervets is kind of exploding right now.” Photo by skibreck/iStock


People may suspect that Christopher Schmitt was drawn to study vervet monkeys because of their intelligence, irresistible cuteness, and curious, most distinctive characteristic: their brilliant blue scrotums. While all these things are fascinating—he does use #BlueScrotumSummer to catalog some of his fieldwork on social media—it’s another feature that attracts scientists like Schmitt to vervets: their genes.

Schmitt, a College of Arts & Sciences assistant professor of anthropology, studies vervets in the wild, and also in a captive colony at Wake Forest University, where most of the monkeys are pedigreed and genotyped. Some of the captive monkeys become obese, a trait uncommon in their wild cousins and of particular interest to Schmitt, who is searching for a genomic role in the disease. “I look at developmental patterns that lead to adult-onset obesity in order to understand better why we become obese,” he says. “And I also work with these animals in the wild so that I can understand the ecological context for these developmental patterns.”

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What does it mean to collect biological samples?
Well, one thing we do is swab all their orifices.

Do you advertise that at the Undergraduate Research Opportunities Program (UROP)? “How would you like to swab a monkey anus?”
Well, my UROP students this summer actually did collect samples fresh from the butt of a vervet monkey in order to get feces that haven’t been contaminated by hitting the ground. The reason we do that is so that we can get a good representation of the microbiome communities inside the gut.

That seems important.
Yes. Especially when talking about obesity. There’s this idea that the ratio of two different families of bacteria—the Firmicutes and the Bacteroidetes—is strongly tied to body condition in humans. People who are obese tend to have a different proportion of those bacteria, versus people who are not obese. We’ve found in other species that this correspondence holds as well. So we’re very interested in how the microbiome in the gut actually does influence body condition in these animals, and we’re planning to compare the gut microbiome of vervets in captivity versus those that are in the wild to see if the gut microbiome can be implicated. On a related note, Duke University researcher Jenny Tung recently found that gene expression patterns are very, very different between two populations of baboons, one that forages on human foods and one that doesn’t, so I’d like to do some work comparing how expression levels of obesity-related genes differ between the captive and wild vervets as well.

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I assume that genomics is not the way people have always studied primates.
No, it’s not.

Does this mean scientists are not going to chase monkeys around in the field anymore? Are you just going to look at data on your computer?
As somebody who really enjoys fieldwork, that’s something I worried about. In my first postdoc, getting more and more into the genomics, I was like, okay, am I going to sit in front of a computer and just run programs in order to understand this variation? Or am I going to be able to take this back to the whole organism and understand it better that way? I really think using a combination of these two approaches, the genotype-forward and the phenotype-back approach, is actually a really great way of keeping more traditional methods of understanding and measuring organismal variation linked to the increasingly micro and data-driven ways we study biology.

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