Burgers and Flies

Inspired by Darwin, Mohamed Noor has uncovered the molecular dance by which a single species becomes two.

May 1, 2012
Megan Scudellari

MOHAMED A. F. NOOR: Earl D. McLean Professor & Associate Chair, Department of Biology, Duke University DUKE UNIVERSITY, CHRIS HILDRETH

Mohamed Noor wasn’t a stellar student at the College of William and Mary in Virginia—until he enrolled in his first genetics class. “I actually put off taking genetics until junior year because people talked about how hard it was,” says Noor. “Then I took it, and I was shocked that it wasn’t hard at all. It was interesting.”

Uncharacteristically, Noor aced genetics, and asked his academic advisor if he should take evolutionary genetics next. “He said, ‘Maybe you should take a class more consistent with your ability. That one’s kind of challenging.’ ” Luckily for evolutionists everywhere, Noor ignored the advice. He enrolled in the class—and spent the whole semester sitting in the front row, recording every lecture and replaying them for himself at the gym each morning. “I was just so enthralled,” Noor recalls with a smile.

Midway through the semester, the professor asked if anyone in the room might want to pursue evolutionary genetics in the future. “I raised my hand confidently, then I looked back and there was not a single other hand raised,” says Noor. “I’m sure they all thought I was a total butt-kisser.”

But Noor had found his calling. “Genetics was full of interesting stories with beautiful logic and mathematical elegance,” he says. In the 20 years since he raised his hand, Noor has been on a quest to answer one of the greatest unsolved questions in biology: How do new species develop? Using Drosophila as a model, Noor has demonstrated how natural selection plays a direct role in preventing two diverging species that live in the same area from blending back together, and he has identified genetic barriers to gene exchange between species. Today, he and his colleagues are teasing apart whole-genome data to determine how recombination rates affect DNA sequence variation within and among species.

Here, Noor shares his secrets about the “easiest fieldwork ever,” how to teach grant writing in 30 minutes, and why he thanks the fast-food chain McDonald’s at the end of lectures.


Master and apprentice. Noor’s inspiring undergraduate professor was none other than Bruce Grant, mentor to a generation of evolutionary biologists including the University of Chicago’s Jerry Coyne, the University of Rochester’s H. Allen Orr, and Stony Brook University’s Walt Eanes, among others. “If it hadn’t been for Bruce Grant, I wouldn’t have made it anywhere. Back in 2005 I wrote a Genetics perspective on him and his contributions to science. His impact on the field is huge. He stimulated all these people to go into evolution. He retired around 2003, and I still keep in touch with him.”

“If it hadn’t been for Bruce Grant, I wouldn’t have made it anywhere.”

Easy breezy. With Grant’s urging, Noor began graduate work in evolutionary genetics with Coyne in Chicago. “One of my first projects was actually one of the biggest things I ever did,” says Noor. He experimentally tested the long-debated hypothesis of reinforcement, in which natural selection reinforces reproductive isolation. In other words, when two populations living in the same area begin to diverge genetically, producing mostly sterile hybrids when they breed, does natural selection reinforce their segregation, as opposed to allowing the two species to blend back together? “When I started the project, Jerry was supportive but pessimistic. He thought it was very likely the answer was going to be negative. But he said go ahead and give it a shot.”

Noor decided to study two closely related fruit fly species that live in the same location in the western United States, but first he needed specimens. “I drove out from Chicago, and it was probably the easiest fieldwork ever. Ecologists would laugh at me. I literally put out buckets of rotting bananas, then went to do something else all day, and came back right at sunset with a net and I was done. Then I’d do the same thing the next day. So I spent all day doing whatever I wanted and did an hour of work at sunrise and sunset.” By analyzing the breeding rates of the two Drosophila species, with individuals of their own species and with each other, Noor determined that natural selection does enhance the reproductive isolation of one species from another—the first experimental evidence of reinforcement contributing to species formation. He published the results in Nature in 1995, a year before he completed his PhD, and was the sole author on the paper. “My advisor, Jerry, had a general policy to let students be sole authors on papers. He said, ‘My job is to give advice. You have to come up with the project, you have to execute it, and you have to write it up. You’ve done all the work, so there’s no reason for my name to be on it.’ That’s uncommon in academia.”

Flipping out. As a young faculty member at Louisiana State University, Noor wanted to identify the genes that made his two species of choice, Drosophila pseudoobscura and Drosophila persimilis, differ from one another. “I wanted to comprehensively map mate preference, the courtship song, hybrid sterility, and traits like that. Two years into the project, we had a lot of data and had identified areas that contributed large effects to every single trait. Unfortunately, every place that contributed to the traits we were studying was a chromosomal inversion—where a stretch of the chromosome is flipped in one species relative to the other. It was extremely frustrating.” Inversions, which are inherited as a block of genes, prevent fine mapping of genes. “It was completely not useful. But then I started thinking and realized it was actually a phenomenon and not just an annoyance.” Noor and his team demonstrated that inversions prevent gene exchange between species, directly causing sterility in cross-species offspring and contributing to speciation. They published the results in PNAS in 2001. “It was surprisingly well received and became my most cited paper,” says Noor. The role of inversions in speciation has since been confirmed in numerous other organisms.

Sweaty palms. In 2008, Noor received a letter in the mail from the Linnean Society of London, announcing that he had won the Darwin-Wallace Medal. “I had no idea what it was, so I Googled it,” says Noor. At the time, the medal was awarded once every 50 years to a handful of scientists who have done the most to advance Darwin’s thinking over the last half century. (Starting in 2010, the medal is now awarded to a single scientist each year.) “I e-mailed them to say I was flattered and to ask who else got it,” he recalls. Other recipients that year included evolution heavyweights Stephen Jay Gould at Harvard and Peter and Rosemary Grant of Princeton. “Then I really felt humbled. Later, they told me they needed one person to respond on behalf of all the medalists, and they asked me. I have no idea why. I don’t think I’ve ever been as nervous for a talk in my life.”

Origin of species. “We now have multiple genome sequences for each Drosophila species, so we’ve confirmed all the primitive-level findings we had in 2001, and every pattern we saw back then has held up.” Noor continues to explore how species diverge. In 2005, he joined the faculty at Duke University in Durham, North Carolina. His lab is now investigating the hypothesis that meiotic drive, a form of non-Mendelian inheritance in which one allele is transmitted to offspring more often than the other allele, causes hybrids to be sterile. “We are finding that to be the case. This is really exciting because it is a theory that has been out there for a long time.” His lab has also overturned accepted dogma in Drosophila genetics: “It was thought for a long time that recombination hotspots—places in a genome where recombination tends to happen, which are well-known in humans and mice—didn’t exist in Drosophila,” he says. “Surprisingly, a graduate student doing a rotation in my lab found a lot of fine-scale variation in recombination rate, way more than anyone had anticipated. Amusingly, she didn’t even end up joining the lab. Nonetheless, her work spawned a huge line of research for us. We’re using the data on how much recombination is occurring at these fine scales and correlating that with patterns of variation in DNA sequences across whole genomes.”


Insta-grant. “In the fall, I teach Grad School 101. It’s basically an introduction to graduate school—things like the peer-review process, how to pick a graduate advisor, and how to write a grant proposal. Every year, I challenge them to help me write a full grant proposal on the board in 30 minutes. Someone picks a topic, and I write it all out. It’s just a small grant, about 500 words. I call it the ‘Insta-grant.’ It’s always crazy stressful, but it works.”

“I love open access. By raising the threshold it takes to [get ahold of] a paper, you’re reducing the number of people who see it and therefore reducing its impact.”

Stress relief. “For a while, my lab had pretty regular water-gun fights. I have a ton of huge water guns, so we’d go to my house, go into the backyard, and spray each other. It’s a good time to have a little fun and vent the frustrations of the day.”

Find a Bruce Grant. “The single biggest piece of advice I give undergraduate biology students is to get into a close mentoring relationship with somebody. Nothing can have a bigger impact on your future than that. Work in their lab. Do research with them.”

The next generation. “I’ve gone into public middle and high schools and asked what students think about evolution. If you go into a 7th-grade classroom, most of them have barely heard the word, don’t know what it is, and don’t have an opinion. You go into the high school, and something like 40 percent of them say it’s wrong. So something clearly happens between 7th and 12th grade. We decided to put together an outreach activity in which students could actually see evolution by natural selection happen. So we made a Drosophila activity and partnered with Carolina Biological Supply [a science-education supply company], who is going to start selling a kit this May. The thing is, you can publish papers full of school activities until the cows come home, but teachers in grade schools are never going to read them. What you need is something so when they’re looking up forceps for fetal pig dissection from the catalog, they’re like, ‘Hey, what’s that?’”

No access. “I love open access. At LSU, there were a lot of journals we just didn’t get. For example, I would see a paper was in the journal Molecular Ecology and groan. If it was something I really, really wanted, I would try to get it by interlibrary loan or chase somebody down or write to the author, but there were a lot of times that I just didn’t see the paper because it wasn’t worth the effort. And LSU is a research university—it’s not some backwoods place. Yes, you can get the paper at some level, but by raising the threshold it takes to get a paper, you’re reducing the number of people who see it and therefore reducing its impact. On the flip side, I am sympathetic to the cost argument. People love to say publishing should all be open access and they shouldn’t have to pay. That sounds nice, but it’s not sustainable. I do make an effort to publish in open-access journals, but I am conscious of the fact that my students and postdocs are applying for jobs. If there’s a prestigious subscription-only journal that I think they can get their research into, I’m sometimes willing to go with that one.”


I’m lovin’ it. “There’s a rumor on the street that I go to McDonald’s every day. I used to go once or twice a week, but lately it hasn’t been that often. I just disproportionally enjoy it every time I go. I also used to have an acknowledgement slide at the end of my seminars saying I acknowledge McDonald’s for caloric support. And I loved the Big N’ Tasty, but they canceled it. Now I get the third-pound Angus burger. That’s good too, but I still miss the Big N’ Tasty.”

iTeaching. “The single biggest thing I love about the iPad is that you can project PowerPoint slides but you still have the spontaneity of the whiteboard. I make a PowerPoint of my lecture and have a little stylus, so I’ll get up there and underline things, circle things, add text, even correct mistakes I’ve made, all while I’m right there. The iPad is just light and streamlined and beautiful.”

Kids say the darndest things. “My parents heavily pushed math and engineering, and I rebelled from it. And I can already see my [7th-grade] daughter deciding she doesn’t like science. So I figure the less I say, the better it will be. If she chooses that route, that’s great. But I don’t want to pressure her and be the reason she doesn’t pick it.”

Chez Noor. “I regularly post on Yelp.com, maybe once every couple of weeks. I like almost any kind of ethnic food. I love Greek and Thai, and Durham is amazing for Mexican food.” Noor has been designated an “elite” Yelp reviewer for the last three years, having posted more than 172 reviews, submitted 321 restaurant photos, and even hosted Yelp events in his home and at Duke. “In addition to reviews, it’s a social thing. Two years ago I hosted a ‘Tour de Taco’ at my house. We got tacos from a bunch of local restaurants, cut them up, and did a blind taste test.”

Like father, like daughter. “My kids are also foodies. When we would go out to eat, my daughter would always order crazy fancy things. Finally, I was like, ‘All right, you need to restrain yourself!’ So I raised her allowance a lot, but said, ‘Now, when we go out to eat, you’re paying your own way.’ So now she saves.”