Duke Research Blog

Following the people and events that make up the research community at Duke.

Category: Biology Page 1 of 22

Stalking Elusive Ferns Down Under

Graduate student Karla Sosa (left) photographs and presses newly collected ferns for later analysis while Ashley Field (in truck) marks the GPS location of the find.

In Queensland, Australia, early March can be 96 degrees Fahrenheit. It’s summer in the Southern Hemisphere, but that’s still pretty hot.

Although hot, dry Australia probably isn’t the first place you’d think to look for ferns, that’s precisely why I’m here and the sole reason we’ve hit the road at 6 a.m. Our schedule for the day: to drive as far south as we can while still letting us come home at the end of the day.

My local colleague, Ashley Field, grew up just the next town over. A skinny, speedy man, he works at James Cook University in Cairns and knows most of northern Queensland like the back of his hand.

Cairns is on the coast at the upper right, where the little green airplane is.

The ferns I’m looking for today are interesting because some species can move from their original home in Australia to the tiny islands in the Pacific. But some cannot. Why? Understanding what makes them different could prove useful in making our crops more resilient to harsh weather, or preventing weeds from spreading.

We’ve been driving for four hours before we turn off onto a dirt road. If you haven’t been to Australia, it’s worth noting that four hours here is unlike any four hours I’ve experienced before. The roads are fairly empty, flat, and straight, meaning you can cover a lot of terrain. Australia is also incredibly big and most of the time you’re travelling through unpopulated landscapes. While it may be only four hours, your mind feels the weight of the distance.

Here’s the one they were looking for!
Cheilanthes tenuifolia with lots of little spore babies on the undersides of its leaves.

The dirt road begins to climb into the mountains. We are leaving behind low scrub and big granite rocks that sit on the flat terrain. Ashley knows where we can find the ferns I’m looking for, but he’s never driven this road before. Instead, we’re trusting researchers who came before us. When they explored this area, they took samples of plants that were preserved and stored in museums and universities. By reviewing the carefully labelled collections at these institutions, we can know which places to revisit in hopes of finding the ferns.

Often, however, having been collected before there was GPS, the location information on these samples is not very precise, or the plants may no longer live there, or maybe that area got turned into a parking lot, as happened to me in New Zealand. So, despite careful planning, you may drive five hours one way to come up empty handed.

As we move higher up the mountain, the soil turns redder and sparse eucalyptus forests begin to enclose us. We locate the previous collections coordinates, an area that seems suitable for ferns to grow. We park the truck on the side of the road and get out to look.

We comb 300 feet along the side of the road because these ferns like the edges of forest, and we find nothing. But as we trudge back to the truck, I spot one meager fern hiding behind a creeping vine! It’s high up off the road-cut and I try to scramble up but only manage to pull a muscle in my arm. Ashley is taller, so he climbs partway up a tree and manages to fetch the fern. It’s not the healthiest, only 6 inches tall for a plant that usually grows at least 12 to 14 inches. It’s also not fertile, making it less useful for research, and in pulling it out of the ground, Ashley broke one of its three leaves off. But it’s better than nothing!

This delicate beauty has no name yet. Karla has to compare it to other ferns in the area to know whether it’s just an odd-looking variant or possibly … a new species!

Ashley excels at being a field botanist because he is not one to give up. “We should keep looking,” he says despite the sweat dripping down our faces.

We pile back in and continue up the road. And who could have predicted that just around the bend we would find dozens of tall, healthy looking ferns! There are easily fifty or so plants, each a deep green, the tallest around 12 inches. Many others are at earlier stages of growth, which can be very helpful for scientists in understanding how plants develop. We take four or five plants, enough to leave a sample at the university in Cairns and for the rest to be shipped back to the US. One sample will be kept at Duke, and the others will be distributed amongst other museums and universities as a type of insurance.

The long hours, the uncertainty, and the harsh conditions become small things when you hit a jackpot like this. Plus, being out in remote wilderness has its own soothing charm, and chance also often allows us to spot cool animals, like the frilled lizard and wallaby we saw on this trip.

Funding for this type of fieldwork is becoming increasingly rare, so I am grateful to the National Geographic Society for seeing the value in this work and funding my three-week expedition. I was able to cover about 400 miles of Australia from north to south, visiting twenty-four different sites, including eight parks, and ranging from lush rainforest to dry, rocky scrub. We collected fifty-five samples, including some that may be new species, and took careful notes and photographs of how these plants grow in the wild, something you can’t tell from dried-up specimens.

Knowing what species are out there and how they exist within the environment is important not only because it may provide solutions to human problems, but also because understanding what biodiversity we have can help us take better care of it in the future.

Guest Post by graduate student Karla Sosa

Malaria Hides In People Without Symptoms

It seems like the never-ending battle against Malaria just keeps getting tougher. In regions where Malaria is hyper-prevalent, anti-mosquito measures can only work so well due to the reservoir that has built up of infected humans who do not even know they carry the infection.

In high-transmission areas, asymptomatic malaria is more prevalent than symptomatic malaria. Twenty-four percent of the people in sub-Saharan Africa are estimated to harbor an asymptomatic infection, including 38 to 50 percent of the school-aged children in western Kenya. Out of the 219 million malaria cases in 2017 worldwide, over 90%  were in sub-Saharan Africa.  

Using a special vacuum-like tool, Kelsey Sumner, a former Duke undergraduate now completing her Ph.D. at UNC-Chapel Hill, collected mosquitoes in households located in rural western Kenya. These weekly mosquito collections were a part of her pre-dissertation study on asymptomatic, or invisible, malaria. She visited Duke in September to catch us up on her work in Data Dialogue event sponsored by the mathematics department.

Sumner and colleague Verona Liao, in front of a sticky trap for mosquitoes

People with asymptomatic malaria carry the infection but have no idea they do because they do not have any indicators. This is incredibly dangerous because without symptoms, they will not get treated and can then infect countless others with the disease. As a result, people with an asymptomatic infection or infections have become a reservoir for malaria — a place for it to hide. Reservoirs are a group that is contributing to transmission at a higher rate or proportion than others.

Sumner’s study focused on examining the effect of asymptomatic malaria on malaria transmission as well as whether asymptomatic malaria infections would protect a person against future symptomatic infections from the same or different malaria infections. They were particularly looking into Plasmodium falciparum malaria. In Kenya, more than 70% of the population lives in an area with a high transmission of this potentially lethal parasite.

“P. falciparum malaria is very diverse in the region,” she said. “It’s constantly mutating, which is why it’s so hard to treat. But because of that, we’re able to actually measure how many infections people have at once.” 

The researchers discovered that many study participants were infected with multiple, genetically-distinct malaria infections. Some carried up to fourteen strains of the parasite.

Participants in the study began by filling out an enrollment questionnaire followed by monthly questionnaires and dried blood spot collections. The project has collected over nearly 3,000 dried blood spots from participants. These blood spots were then sent to a lab where DNA was extracted and tested for P. falciparum malaria using qPCR

“We used the fact that we have this really diverse falciparum species in the area and sequenced the DNA from falciparum to actually determine how many infections people have,” Sumner said. “And then, if there’s a shared infection between humans and mosquitoes.”

Sumner and her team also visited symptomatic participants who would fill out a behavioral questionnaire and undergo a rapid diagnostic test. Infected participants were able to receive treatment. 

While people in the region have tried to prevent infection through means like sleeping under insecticide-treated nets, malaria has persisted. 

One of the Kenyan staff members hanging a CDC light trap for mosquitoes

Sumner is continuing to analyze the collected DNA to better understand asymptomatic malaria, malarial reservoirs and how to best intervene to help stop this epidemic. 

“We’re basically looking at how the number of shared infections differ between those that have asymptomatic malaria versus those that have symptomatic malaria.”

She and her team hypothesize that there are more asymptomatic infections that would result in and explain the rapid transmission of malaria in the region.

Post by Anna Gotskind

Meet the New Blogger: Meghna Datta

Hi! My name is Meghna Datta, and I’m a freshman. I’m from Madison, Wisconsin, so North Carolina weather has been quite the adjustment. Apart from the humidity, though, I’m so excited to be at Duke! I’m an aspiring pre-med student with absolutely no idea what I want to major in. And it’s funny that I’ve grown to love science as much as I do. Up until tenth grade, I was sure that I would never, ever work in STEM.

My first love was the humanities. As a child I was hooked on books (still am!) and went through four or five a week. In high school, I channeled my love for words into joining my school’s speech and debate team and throwing myself into English and history classes, until being forced to take AP Biology my sophomore year completely changed my trajectory.

Science had always bored me with its seemingly pointless intricacies. Why would I want to plod through tedious research when I could be covering a groundbreaking story or defending justice in a courtroom instead? But the lure of biology for me was in its societal impact. Through research, we’ve been able to cure previously incurable diseases and revolutionize treatment plans to affect quality of life.

Meghna Datta repping the Devils

In AP Bio, understanding the mechanisms of the human body seemed so powerful to me. Slowly, I began to entertain the notion of a career in medicine, one of many scientific fields that works to improve lives every day.

Now, the research going on at Duke doesn’t cease to amaze me. Specifically, I’m interested in science for social good. Be it sustainable engineering, global health, or data-driven solutions to problems, I love to see the ways in which science intersects with social issues. As I have learned, science does not need to be done in isolation behind pipettes. Science is exciting and indicative of society’s shared sense of humanity. At Duke, there’s no shortage of this environment.

As a blogger I’m so excited to see the inspiring ways that peers and faculty are working to solve problems. And because science isn’t a traditionally “showy” field, I am looking forward to shining the spotlight on people at Duke who tirelessly research behind the scenes to impact those at Duke and beyond. The research community at Duke has so much to celebrate, and through blogging I’m excited to do just that!

Legendary Paleontologist Richard Leakey Visits Duke

Hoping to catch up with an old friend who is a professor at Duke, Richard Leakey accepted an invitation to speak at the university on Oct. 22, though he “gave up public speaking to a large extent many years ago.”

Richard E. Leakey visited Duke on Oct. 22, 2019.

Leakey, age 74, is a world-renowned pioneer in Paleoanthropology – the study of the human fossil record – and is also well-known for his involvement in Kenyan politics and lifelong efforts towards conservation and wildlife protection. Once, he famously burned twelve tons of elephant tusks that were confiscated from poachers, which gathered international attention and helped usher in a global ban on the ivory trade.

Leakey came to paleontology by heredity. He is one of an entire family of Paleo-pioneers. His mother, Mary, discovered a skull in Africa that was dated to 1.75 million years ago (MYA) in 1960. Leakey said that this “electrified interest in the origin story” – that is, the human origin story. When his father, Louis, showed that the “quite clever” ancient tools he had discovered were made around 1.75 MYA, the original idea that human origins began outside of Africa began to change.

Leakey said the British people were hoping that “if we had evolved … let it happen in England” and if not England, then Asia, but this was not to be the case. At first, Louis Leakey was ostracized because of his work and discoveries of human origins in Africa. This helped steer Richard away from academics because of the fights that he saw his father endure.

Leakey’s famous 1984 Kenyan discovery, “Turkana Boy,” a 1.5 million-year-old, nearly-complete specimen of Homo erectus. (Wikipedia)

Successfully achieving his self-described ambition to not finish high school, Richard Leakey was thrown out of school at age 16. Yet today he is accredited with many awards, has written at least eight books, and has advanced the Leakey family legacy of discovery. From 1968 to the present day, he and fellow workers have discovered enormous numbers of fossils of our ancestors along the East and West shores of Lake Turkana in Kenya, which have an age span from 4.5 MYA to our very recent ancestors, which Leakey calls “fossil us.”

Leakey described for the Duke audience in an overflowing auditorium at the Nasher Museum a scenario he facilitated with colleagues and students.

He had taken a group to a camp site to talk about evolution and asked them to perform some tasks. First, they were charged to make tools from stone. The following day, they were led to a freshly slaughtered goat. Leakey told his pupils to butcher the goat and remove the flesh from its carcass.

After several hours watching the individuals try to pull at the goat with their hands to no avail, Leakey suggested that they might use their new stone tools. So they did, but they still could not get through the animal’s tough hide, even with a blade.

He said that during human evolution, our imagination was turned on genetically and this gave early humans the “capability to think of things that weren’t.” There is lots of work to be done studying an ancient period over 3.5 million years that Leakey says lends itself to “early ancestry of speech, imagination, [and] cooperation.” He is hopeful for the knowledge and new understandings that will come from investigation of this period. 

“Why not ask someone to help you?” Leakey prompted again, and within an hour, nothing was left of the goat. The exercise demonstrated that though other monkeys and apes use stone, it is the human’s vocal communication and sense of working together that sets us apart, says Leakey.     

Leakey’s current project is a “mega-museum” to “cerebrate and celebrate the story of the African origin.” The origin story which his parents first provided crucial evidence for is hugely important to the African continent and to the people of Africa and because we have “desecrated our motherland,” he said. Leakey wants the museum to highlight stages of evolution, genetics, climate, ecology, other species, and extinctions.

An architectural rendering of Ngaren: The Museum of Humankind to be built near Nairobi. (Studio Libeskind )

Before moving into the panel and Q&A portion of his talk, which was moderated by Duke professors Steven Churchill and Anne Yoder, Leakey prompted the audience to think about climate change, asking why we do not think we need to save ourselves. If we die, then other species go with us.

“Don’t for a minute think that climate change isn’t a real crisis that we’re in together,” Leakey said, earning a round of applause.

Post by Cydney Livingston

These Microbes ‘Eat’ Electrons for Energy

The human body is populated by a greater number of microbes than its own cells. These microbes survive using metabolic pathways that vary drastically from humans’.

Arpita Bose’s research explores the metabolism of microorganisms.

Arpita Bose, PhD, of Washington University in St. Louis, is interested in understanding the metabolism of these ubiquitous microorganisms, and putting that knowledge to use to address the energy crisis and other applications.

Photoferrotrophic organisms use light and electrons from the environment as an energy source

One of the biggest research questions for her lab involves understanding photoferrotrophy, or using light and electrons from an external source for carbon fixation. Much of the source of energy humans consume comes from carbon fixation in phototrophic organisms like plants. Carbon fixation involves using energy from light to fuel the production of sugars that we then consume for energy.

Before Bose began her research, scientists had found that some microbes interact with electricity in their environments, even donating electrons to the environment. Bose hypothesized that the reverse could also be true and sought to show that some organisms can also accept electrons from metal oxides in their environments. Using a bacterial strain called Rhodopseudomonas palustris TIE-1 (TIE-1), Bose identified this process called extracellular electron uptake (EEU).

After showing that some microorganisms can take in electrons from their surroundings and identifying a collection of genes that code for this ability, Bose found that this ability was dependent on whether a light source was also present. Without the presence of light, these organisms lost 70% of their ability to take in electrons.   

Because the organisms Bose was studying can rely on light as a source of energy, Bose hypothesized that this dependence on light for electron uptake could signify a function of the electrons in photosynthesis.  With subsequent studies, Bose’s team found that these electrons the microorganisms were taking were entering their photosystem.

To show that the electrons were playing a role in carbon fixation, Bose and her team looked at the activity of an enzyme called RuBisCo, which plays an integral role in converting carbon dioxide into sugars that can be broken down for energy. They found that RuBisCo was most strongly expressed and active when EEU was occurring, and that, without RuBisCo present, these organisms lost their ability to take in electrons. This finding suggests that organisms like TIE-1 are able to take in electrons from their environment and use them in conjunction with light energy to synthesize molecules for energy sources.  

In addition to broadening our understanding of the great diversity in metabolisms, Bose’s research has profound implications in sustainability. These microbes have the potential to play an integral role in clean energy generation.

Post by undergraduate blogger Sarah Haurin
Post by undergraduate blogger Sarah Haurin

Combining Up-Close Views of Science, Nature With the Magic of Light

Zinnia stamen by Thomas Barlow, Duke University

Thomas Barlow ’21 finds inspiration in small everyday things most people overlook: a craggy lichen growing on a tree, a dead insect, the light reflected by a pane of glass. Where we might see a flower, Barlow looks past the showy pink petals to the intricate parts tucked within.

The 20-year-old is a Duke student majoring in biology. By day, he takes classes and does research in a lab. But in his spare time, he likes to take up-close photographs using objects he finds outside or around the lab: peach pits, fireflies. But also pipettes, pencils.

A handheld laser pointer and flitting fireflies become streaks of light in this long-exposure image in Duke Forest. By Thomas Barlow.

Barlow got interested in photography in middle school, while playing around with his dad’s camera. His dad, a landscape architect, encouraged the hobby by enlisting him to take photos of public parks, gardens and playgrounds, which have been featured on various architects’ websites and in national publications such as Architecture Magazine. But “I always wanted to get closer, to see more,” Barlow said.

In high school he started taking pictures of still lifes. But he didn’t just throw flowers and fruit onto a backdrop and call it art. His compositions were a mishmash of insects and plants arranged with research gadgets: glass tubes, plastic rulers, syringes, or silicon wafers like those used for computer chips.

“I like pairing objects you would never find together normally,” Barlow said. “Removing them from their context and generating images with interesting textures and light.”

Sometimes his mother sends him treasures from her garden in Connecticut to photograph, like the pale green wings of a luna moth. But mostly he finds his subjects just steps from his dorm room door. It might be as easy as taking a walk through Duke Gardens or going for one of his regular runs in Duke Forest.

Having found, say, a flower bud or bumblebee, he then uses bits of glass, metal, mirrors and other shiny surfaces — “all objects that interact with light in some interesting way” – to highlight the interaction of light and color.

“I used to be really obsessed with dichroic mirrors,” pieces of glass that appear to change colors when viewed from different angles, Barlow said. “I thought they were beautiful objects. You can get so many colors and reflections out of it, just by looking at it in different ways.”

In one pair of images, the white, five-petaled flowers of a meadow anemone are juxtaposed against panels of frosted glass, a pipette, a mechanical pencil.

Another image pair shows moth wings. One is zoomed in to capture the fine details of the wing scales. The other zooms out to show them scattered willy-nilly around a shimmering pink circle of glass, like the remnants of a bat’s dinner plate.

Luna moth wings and wing scales with dichroic mirror, Thomas Barlow

For extreme close-ups, Barlow uses his Canon DSLR with a microscope objective mounted onto the front of a tube lens. Shooting this close to something so small isn’t just a matter of putting a bug or flower in front of the camera and taking a shot. To get every detail in focus, he takes multiple images of the same subject, moving the focal point each time. When he’s done he’s taken hundreds of pictures, each with a different part of the object in focus. Then he merges them all together.

At high magnification, Barlow’s flower close-ups reveal the curly yellow stamens of a zinnia flower, and the deep red pollen-producing parts of a tiger lily.

“I love that you can see the spikey pollen globules,” Barlow said.

Stomata and pollen on the underside of a tiger lily stamen, by Thomas Barlow

When he first got to Duke he was taking photos using a DIY setup in his dorm room. Then he asked some of the researchers and faculty he knew if there was anything photography-related he could do for their labs.

“I knew I was interested in nature photography and I wanted to practice it,” Barlow said.

One thing led to another, and before long he moved his setup to the Biological Sciences building on Science Drive, where he’s been photographing lichens for Daniele Armaleo and Jolanta Miadlikowska, both lichenologists.

“A lichen photo might not seem like anything special to an average person,” Barlow said. “But I think they’re really stunning.”

Love at First Whiff

Many people turn to the Internet to find a Mr. or Ms. Right. But lemurs don’t have to cyberstalk potential love interests to find a good match — they just give them a sniff.

A study of lemur scents finds that an individual’s distinctive body odor reflects genetic differences in their immune system, and that other lemurs can detect these differences by smell.

Smell check: Fritz the ring-tailed lemur sniffs a tree for traces of other lemurs’ scents at the Duke Lemur Center.
Smell check: Fritz the ring-tailed lemur sniffs a tree for traces of other lemurs’ scents. Photo by David Haring, Duke Lemur Center.

From just one whiff, these primates are able to tell which prospective partners have immune genes different from their own. The ability to sniff out mates with different immune genes could make their offspring’s immune systems more diverse and able to fight more pathogens, said first author Kathleen Grogan, who did the research while working on her Ph.D. with professor Christine Drea at Duke University.

The results appeared online August 22 in the journal BMC Evolutionary Biology.

Lemurs advertise their presence by scent marking — rubbing stinky glands against trees to broadcast information about their sex, kin, and whether they are ready to mate.

Lemurs can tell whether a mate’s immune genes are a good genetic match by the scents they leave behind.
Lemurs can tell whether a mate’s immune genes are a good genetic match by the scents they leave behind. Photo by David Haring, Duke Lemur Center

For the study, Grogan, Drea and colleagues collected scent secretions from roughly 60 lemurs at the Duke Lemur Center, the Indianapolis Zoo, and the Cincinnati Zoo. The team used a technique called gas chromatography-mass spectrometry to tease out the hundreds of compounds that make up each animal’s signature scent.

They also analyzed the lemurs’ DNA, looking for differences within a cluster of genes called MHC that help trigger the body’s defenses against foreign invaders such as bacteria and viruses.

Their tests reveal that the chemical cocktail lemurs emit varies depending on which MHC types they carry.

To see if potential mates can smell the difference, the researchers presented lemurs with pairs of wooden rods smeared with the bodily secretions of two unfamiliar mates and observed their responses. Within seconds, the animals were drawn to the smells wafting from the rods, engaging in a frenzy of licking, sniffing, or rubbing their own scents on top.

In 300 trials, the team found that females paid more attention to the scents of males whose immune genes differed from their own.

MHC genes code for proteins that help the immune system recognize foreign invaders and distinguish “friend” from “foe.” Since different genetic versions respond to different sets of foreign substances, Grogan said, sniffing out genetically dissimilar mates produces offspring more capable of fighting a broad range of pathogens.

Just because females spent more time checking out the scents of dissimilar males doesn’t necessarily make them more likely to have kids together, Grogan said. Moving forward, she and her colleagues plan to use maternity and paternity DNA test results from wild lemurs living in Beza Mahafaly Reserve in Madagascar to see if lemur couples are more different in their MHC type than would be expected by chance.

Similar results have been found in humans, but this is the first time the ability to sniff out partners based on their immune genes has been shown in such distant primate kin, said Grogan, who is currently a postdoctoral fellow at Pennsylvania State University.

“Growing evidence suggests that primates rely on olfactory cues way more than we thought they did,” Grogan said. “It’s possible that all primates can do this.”

This research was supported by the National Science Foundation (BCS #0409367, IOS #0719003), the National Institutes of Health (F32 GM123634–01), and the Duke University Center for Science Education.

CITATION: “Genetic Variation at MHC class II Loci Influences Both Olfactory Signals and Scent Discrimination in Ring-Tailed Lemurs,” Kathleen E. Grogan, Rachel L. Harris, Marylène Boulet, and Christine M. Drea. BMC Evolutionary Biology, August 22, 2019. DOI: 10.1186/s12862-019-1486-0

Post by Robin A. Smith

Do DNA Tests Sell Rosy Ideas About Race for Profit?

Earlier this year,  the online DNA testing company Ancestry.com faced a media firestorm and social media backlash after posting a controversial ad on its YouTube page.

The DNA testing company Ancestry.com took down its ad, “Inseparable,” in April 2019 in response to criticism that it romanticized slavery.

Titled “Inseparable,” the 30-second ad depicted a white man in the antebellum South asking an African-American woman to flee to the North with him. Before the woman can answer, the piece cuts to a tagline: “Only you can keep the story going. Uncover the lost chapters of your family history with Ancestry.” Many criticized the ad’s historical inaccuracy, showcasing a rosier portrayal of a complicated past. To extinguish flames, Ancestry completely pulled the ad from its platforms.

A recent Duke study of dozens of other ads across multiple DNA testing companies shows that this isn’t the only example of mixed messaging about race and identity from the world of genetic ancestry tests.

The tests are quite simple: order a kit, send off a saliva sample and receive an ethnicity estimate within weeks. A test taker’s ethnicity is broken down into percentages based off their DNA matches compared to a globally referenced DNA database. Kits can range in price from $79 to$400. Sales of DNA testing kits had reached 12 million people by 2017, as reported by ScienceLine.

As part of the six-week summer research program Story+, Duke students Dakota Douglas, Mona Tong and Madelyn Winchester analyzed the messaging in 90 video ads from the companies 23andMe, AncestryDNA and MyHeritageDNA to see what they promise consumers.

Many of the ads lured customers with promises of a newfound identity and possible family members, the team found. One Ancestry.com ad, entitled “Kyle,” depicts a customer whose childhood was steeped in German culture, but discovers as an adult that he is also part Scottish and Irish. He happily “traded in his lederhosen for a kilt,” completely forgoing his previous heritage and reducing a newly discovered culture to stereotypes.

“There were a lot of advertisements similar to that one,” said team member Mona Tong. “Many found a new identity embracing it fully despite a lack of any cultural connections.”

“Kyle” illustrates a phenomenon described in a 2018 study from the University of British Columbia, which found that people tended to “cherry-pick” the results, identifying more with certain ethnicities and cultures to appear different. Whites were more likely to see their results as “transformational” than their nonwhite counterparts.

“It’s not a bad idea to test your genes for medical reasons,” said Patricia Bass, the team’s project mentor. “However, these ads can be misleading by assuming that someone’s cultural and racial heritage are determined by genes.”

While the majority of subjects featured within the ads were white, the few ads that featured people of color often glossed over the complicated history of someone’s lineage or conveniently left out difficult topics. Ancestry’s “Anthem” ad detailed historical reenactments of an African tribal women, prohibition gangsters, a man fleeing England for America and Native Americans somberly heading to a new land. A voiceover speaks with inspiration ending with a shot of a biracial woman.

In marketing the idea that we are all one, the ads fetishized mixed-race subjects, while ignoring the genocide and displacement of people, the team found.

The team hopes future research will further examine the impact of these ads on people’s view of identity. Importantly, one could note if there were any focus groups to test these ads before release.

“It furthers the idea of colorblindness,” Tong said. “It assumes that relationships are contingent upon common ancestry and genes.”

“In a way, companies are trying to help by focusing on the interconnectivity and commonalities between people,” Tong said. “But it hurts more than it helps.”

Story+ is a six-week undergraduate research program offered through the John Hope Franklin Humanities Institute and Bass Connections, with support from the Duke University Libraries and Versatile Humanists at Duke.

By Deja Finch

Overdiagnosis and the Future of Cancer Medicine

For many years, the standard strategy for fighting against cancer has been to find it early with screening when the person is still healthy, then hit it with a merciless treatment regimen to make it go away.

But not all tumors will become life-threatening cancers. Many, in fact, would have caused no issues for the rest of the patients’ lives had they not been found by screening. These cases belong to the category of overdiagnosis, one of the chief complaints against population-level screening programs.

Scientists are reconsidering the way to treat tumors because the traditional hit-it-hard approach has often caused the cancer to seemingly go away, only to have a few cells survive and the entire tumor roar back later with resistance to previously effective medicine.

Dr. Marc Ryser, the professor who gave this meaty talk

In his May 23 talk to Duke Population Health, “Cancer Overdiagnosis: A Discourse on Population Health, Biologic Mechanism and Statistics,” Marc Ryser, an assistant professor at Duke’s Departments of Population Health Sciences and Mathematics, walked us through how parallel developments across different disciplines have been reshaping our cancer battle plan. He said the effort to understand the true prevalence of overdiagnosis is a point of focus in this shift.

Past to Future: the changing cancer battle plan
Credit: Marc Ryser, edit: Brian Du

Ryser started with the longstanding biological theory behind how tumors develop. Under the theory of clonal sweeps, a relatively linear progression of successive key mutations sweeps through the tumor, giving it increasing versatility until it is clinically diagnosed by a doctor as cancer.

Clonal sweeps model, each shade is a new clone that introduces a mutation credit: Sievers et al. 2016

With this as the underpinning model, the battle plan of screen early, treat hard (point A) makes sense because it would be better to break the chain of progression early rather than later when the disease is more developed and much more aggressive. So employing screening extensively across the population for the various types of cancer is the sure choice, right?

But the data at the population level for many different categories of cancers doesn’t support this view (point B). Excluding the cases of cervical cancer and colorectal cancer, which have benefited greatly from screening interventions, the incidence of advanced cases of breast cancer and other cancers have stayed at similar levels or actually continued to increase during the years of screening interventions. This has raised the question of when screening is truly the best option.

Scientists are thinking now in terms of a “benefit-harm balance” when mass-screening public health interventions are carried out. Overdiagnosis would pile up on the harms side, because it introduces unnecessary procedures that are associated with adverse effects.

Thinking this way would be a major adjustment, and it has brought with it major confusion.

Paralleling this recent development on the population level, new biological understanding of how tumors develop has also introduced confusion. Scientists have discovered that tumors are more heterogeneous than the clonal sweeps model would make it appear. Within one tumor, there may be many different subpopulations of cancer cells, of varying characteristics and dangerousness, competing and coexisting.

Additional research has since suggested a more complex, evolutionary and ecological based model known as the Big Bang-mutual evolution model. Instead of the “stepwise progression from normal to increasingly malignant cells with the acquisition of successive driver mutations, some cancers appear to evolve more like a Big Bang, where the malignant ability is already concentrated in the founder cell,” Ryser said.

As the first cell starts to replicate, its descendants evolve in parallel into different subpopulations expressing different characteristics. While more research has been published in favor of this model, some scientists remain skeptical.

Ryser’s research contributes to this ongoing discussion. In comparing the patterns by which mutations are present or absent in cancerous and benign tumors, he obtained results favoring the Big Bang-mutual evolution model. Rather than seeing a neat region of mutation within the tumor, which would align with the clonal sweeps model, he saw mutations dispersed throughout the tumor, like the spreading of newborn stars in the wake of the Big Bang.

How to think about mutations within a tumor
credit: NASA

The more-complicated Big Bang-mutual evolution model justifies an increasingly nuanced approach to cancer treatment that has been developing in the past few years. Known as precision medicine (point C), its goal is to provide the best treatment available to a person based on their unique set of characteristics: genetics, lifestyle, and environment. As cancer medicine evolves with this new paradigm, when to screen will remain a key question, as will the benefit-harm balance.

There’s another problem, though: Overdiagnosis is incredibly hard to quantify. In fact, it’s by nature not possible to directly measure it. That’s where another area of Ryser’s research seeks to find the answers. He is working to accurately model overdiagnosis to estimate its extent and impact.

Going forward, his research goal is to try to understand how to bring together different scales to best understand overdiagnosis. Considering it in the context of the multiscale developments he mentioned in his talk may be the key to better understand it.

Post by Brian Du

Pot Not So Harmless for Teens

Marijuana is becoming legalized and decriminalized to the point that more than 63 percent of Americans have access to medical and recreational cannabis. But researchers and policy experts still don’t know very much about the long-term health effects.

The 2019 annual symposium by Duke’s Center on Addiction & Behavior Change,  “Altered States of Cannabis Regulation: Informing Policy with Science,” provided some scientific answers. Madeline Meier, assistant professor of Psychology at Arizona State University and a former Duke post-doc, spoke about her longitudinal research projects that offer critical insights about the long-term effects of cannabis use.

Meier investigates the relationship between cannabis use and IQ in a 38-year-long study that has been collecting data on a group of 1,000 people born in New Zealand since birth. Longitudinal studies like this that follow the same group of individuals across their lifespan are vital to understanding the effects of extended cannabis use on the human body, but they are difficult to conduct and keep funded. The 95 percent retention rate of this study is quite impressive and provides much-needed data.


Madeline Meier of Arizona State University

The researchers had tested the babies’ IQ at early childhood, then conducted regular IQ and cannabis use assessments between the ages of 18 and 38. They found that participants who heavily used weed for extended periods of time experienced a significant IQ drop, as well as other impairments in learning and memory skills. Specifically, users who had three or more clinical diagnoses of cannabis dependency, defined as compulsive use despite physical, legal, or social problems caused by the drug, showed an average 6-point IQ drop over the years. Those who only tried the drug a few times showed no decline, and those who never used weed showed a 1-point IQ increase.

Notably, however, the results depended on age of onset and level of use. Meier emphasized that her results do not support the common misconception that any amount of weed use can immediately lead to IQ decline. To the contrary, Meier’s team found that short-term, low-level use did not have any effect on IQ; only heavy users suffered the negative effects. The age of onset of cannabis use was critical, too: Adolescents were more vulnerable to the drug’s harms, with study participants who started using as adolescents showing an 8-point drop in IQ points. Given what we know about adolescents’ affinity for risky behavior, specifically around experimentation with drugs, this finding is particularly worrisome.

In addition to causing cognitive impairment, persistent cannabis use jeopardizes people’s psychosocial functioning as well. The Dunedin longitudinal study has also revealed that people who continued to use weed despite multiple dependency diagnoses experienced downward social mobility, relationship problems, antisocial workplace behavior, financial difficulties, and even higher numbers of traffic convictions. In short, social life is likely to be perilous for heavy weed users.

While some have suggested that the harmful effects of weed might be caused not by the drug itself but by the reduced years of education, low socioeconomic status, mental health problems, or simultaneous use of tobacco, alcohol or other drugs among weed users, Meier and her team found that the impairments persisted even when these factors were accounted for. Cannabis alone was responsible for the effects reflected in Meier’s research. In fact, there is limited evidence for the opposite causational link: weed use may be the cause of mental health problems rather than being caused by them. One study found a weak correlation between years of marijuana use and depression, but Meier was careful to point out that it would take “a lot of cannabis use to lead to clinically diagnosed depression.”

Given this data, Meier called on the policy-makers in the room to focus their efforts on delaying the onset of cannabis use in youth and encouraging cessation (especially among adolescents). In appealing to the researchers, she underlined the need for additional longitudinal studies into the mechanisms and parameters of cannabis use that produce long-term impairments.

As public and political support of marijuana legalization grows, we must be careful not to underestimate the dangers of the drug. Without knowing the full extent of the risks and benefits of weed, policy-makers cannot effectively promote public health, safety, and social equity.

Guest Post by Deniz Ariturk

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