The Knowledge
Mosquitoes carrying malaria are evolving more quickly than insecticides can kill them – researchers pinpoint how
Jacob A Tennessen, Harvard University
The fight against infectious disease is a race against evolution. Bacteria become resistant to antibiotics. Viruses adapt to spread more quickly. Diseases transmitted by insects present another evolutionary front: Insects themselves can evolve resistance to the poisons that people use to kill them.
In particular, the mosquito-borne disease malaria kills over 600,000 people annually. Since World War II, people have battled malaria with insecticides – chemical weapons intended to kill Anopheles mosquitoes infected with the Plasmodium parasites that cause the disease.
However, mosquitoes are quickly evolving counterstrategies that make these insecticides ineffective, putting millions of people at greater risk of deadly infection. My colleagues and I have newly published research showing how.
Insecticide resistance threatens public health
As an evolutionary geneticist, I study natural selection – the basis for adaptive evolution. Genetic variants that best promote survival can replace less advantageous versions, causing species to change. Anopheles mosquitoes are frustratingly adept at evolving.
In the mid-1990s, most African Anopheles were susceptible to pyrethroids, a popular type of insecticide originally derived from chrysanthemums. Anopheles control relies on two pyrethroid-based methods: insecticide-treated bed nets to protect sleepers, and indoor residual spraying of insecticide against the walls of homes. These two methods alone likely prevented over a half-billion cases of malaria between 2000 and 2015.
However, mosquitoes today from Ghana to Malawi are often able to survive insecticide concentrations 10 times the previously lethal dose. Along with Anopheles control efforts, agriculture also inadvertently exposes mosquitoes to pyrethroids and contributes to insecticide resistance.
In some African locales, Anopheles is already showing resistance to all four main classes of insecticide used for malaria control.
Adaptation in Latin American mosquitoes
Anopheles mosquitoes and the malaria-causing Plasmodium also occur outside Africa, where insecticide resistance is less well-researched.
In much of South America, the main malaria vector is Anopheles darlingi. This mosquito species has diverged evolutionarily from the African vectors so extensively that it might be a different genus, Nyssorhynchus. Along with colleagues from eight countries, I analyzed over 1,000 Anopheles darlingi genomes to understand its genetic diversity, including any recent changes due to human activity. My collaborators collected these mosquitoes at 16 locations ranging from the Atlantic coast of Brazil to the Pacific side of the Andes in Colombia.
We found that, like its African counterparts, Anopheles darlingi shows extremely high genetic diversity – more than 20 times that of humans – indicating that very large populations of this insect exist. A species with such a vast gene pool is well poised to adapt to new challenges. The right mutation giving it the advantage it needs is more likely to pop up when there are so many individuals. And once that mutation starts to spread, it’s protected by numbers since it won’t be wiped out if a few mosquitoes die by chance.
In contrast, bald eagles in the contiguous U.S. were never able to evolve resistance against the insecticide DDT and approached extinction. Evolution is more efficient among millions of insects than mere thousands of birds. And indeed, we saw signals of adaptive evolution in the resistance-related genes of Anopheles darlingi occurring over the past few decades.
Mosquitoes evolve to detoxify poisons
Insecticides like pyrethroids and DDT share the same molecular target: channels in nerve cells that can open and close. When open, the nerve cell stimulates other cells. These insecticides force the channels to remain open and continuously fire, causing paralysis and death. However, insects can evolve resistance by changing the shape of the channel itself.
Earlier genetic scans performed by other researchers had not detected this type of resistance in Anopheles darlingi, and neither did ours. Instead, we found that resistance is evolving in another way: a group of genes encoding enzymes that break down toxic compounds. High activity of these enzymes, called P450, frequently underlies resistance to insecticides in other mosquitoes. The same cluster of P450 genes has changed independently at least seven times across South America since insecticide use began in the mid-20th century.
In French Guiana, a different set of P450 genes exhibits a similar evolutionary pattern, cementing the clear connection between these enzymes and adaptation. Moreover, when we exposed mosquitoes to pyrethroids in sealed bottles, differences among the P450 genes of individual mosquitoes were linked to the length of time they stayed alive.
Insecticide-heavy campaigns against malaria have been only sporadic in South America and may not be the main driver behind this evolution. Instead, it’s possible that mosquitoes are being exposed indirectly to agricultural insecticides. Intriguingly, we saw the strongest signs of evolution in places where farming is prevalent.
Toward more sophisticated vector control
Despite new vaccines and other recent advances against malaria, mosquito control remains essential for reducing disease.
Some countries are launching trials of gene drives to control malaria, which involve forcing a genetic modification into a mosquito population to reduce their numbers or their tolerance for Plasmodium. Such prospects are exciting, though the relentless adaptability of mosquitoes could be an obstacle.
I and others are revising methods to efficiently test for emerging insecticide resistance. Genome-scale sequencing remains important to detect new or unexpected evolutionary responses. The risk of adaptation is highest under a continuous, strong selection pressure, so minimizing, switching and staggering pesticides can help thwart resistance.
Success in the fight against evolving resistance will require a coordinated effort of monitoring, and reacting accordingly. Unlike evolution, humans can think ahead.
Jacob A Tennessen, Research Scientist in Immunology and Infectious Diseases, Harvard University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Forgotten Genius Fridays
Forgotten Genius Friday: Madam C. J. Walker Built an Empire—and Opened Doors for Thousands
Born Sarah Breedlove to formerly enslaved parents, Madam C. J. Walker rose from poverty to build a national beauty business and create economic opportunities for thousands of Black women. Her remarkable journey transformed her into one of America’s greatest entrepreneurial pioneers.
Long before beauty brands became billion-dollar businesses and decades before women—especially Black women—had widespread access to business financing and professional opportunities, Madam C. J. Walker was building an empire of her own.
Born Sarah Breedlove in Louisiana in 1867, Walker rose from poverty and years of physically demanding work to become one of America’s most successful entrepreneurs.
Her achievement wasn’t simply about accumulating wealth.
Walker created products for an underserved community, developed an innovative nationwide sales network, trained thousands of women to become financially independent, and used her success to support civil rights and charitable causes.
Her journey remains one of the most remarkable stories in American business history.
From Sarah Breedlove to Madam C. J. Walker
Sarah Breedlove was born December 23, 1867, near Delta, Louisiana.
Her parents, Owen and Minerva Breedlove, had been enslaved, making Sarah the first of their children born into freedom following the Civil War.
Her childhood was difficult. Both of her parents died while she was young, leaving her orphaned at about seven years old.
She married at 14 and became a mother at 17. After the death of her first husband, she eventually moved with her daughter, Lelia—later known as A’Lelia Walker—to St. Louis.
There, Sarah worked as a washerwoman, reportedly earning little more than a dollar a day.
But she was determined to give her daughter something she herself had been denied: an education.
A Personal Problem Becomes a Business Idea
Around the turn of the 20th century, Walker began experiencing severe scalp problems and hair loss.
These conditions were common among many women at the time. Limited access to indoor plumbing, harsh soaps, poor nutrition, and inadequate hair-care products could contribute to scalp disease and hair loss.
Walker began experimenting with treatments while also learning about the growing Black hair-care industry.
She briefly worked as a sales agent for Annie Turnbo Malone, another pioneering Black entrepreneur whose Poro hair-care company became enormously successful.
That experience helped Walker understand both hair care and the potential of direct-to-consumer sales.
After moving to Denver, Sarah began developing and selling her own products.
Following her marriage to newspaper advertising salesman Charles Joseph Walker, she began doing business under the name that would become famous:
Madam C. J. Walker.
The “Walker System”
Walker didn’t simply sell jars of hair products.
She sold a complete hair-care method.
Known as the Walker System, it emphasized scalp cleanliness and healthy hair through regular washing, specialized products, heated combs, and careful grooming.
One of her best-known products was Madam Walker’s Wonderful Hair Grower, a scalp-conditioning treatment.
But perhaps Walker’s greatest innovation wasn’t contained inside a jar.
It was her business model.
Creating an Army of Women Entrepreneurs
Walker developed a network of independent saleswomen known as Walker Agents.
Women were trained not only to use and demonstrate Walker products but also to operate their own small businesses.
They sold products directly to customers, demonstrated hair-care techniques, and built relationships within their communities.
For Black women living in an era when employment opportunities were severely restricted by both racism and sexism, the Walker organization offered something extraordinary:
A pathway toward financial independence.
Thousands of women eventually became associated with the Walker sales network.
Walker also established training programs and beauty schools where women learned hair care, sales techniques, personal presentation, and business skills.
In many ways, the Walker Agents represented an early nationwide network of women-owned microbusinesses.
Building a Manufacturing Empire
As demand increased, Walker expanded her operation.
In 1910, she moved the headquarters of the Madam C. J. Walker Manufacturing Company to Indianapolis, Indiana.
The city offered strong transportation connections and access to a growing Black business community.
Her operation eventually included manufacturing facilities, a laboratory, training schools, mail-order operations, and a national network of sales representatives.
Walker became one of the most prominent Black business leaders in America.
Her success was particularly remarkable considering that she had begun her adult life working as a washerwoman.
Was Madam C. J. Walker America’s First Female Self-Made Millionaire?
Walker is frequently described as America’s first female self-made millionaire.
That description has become an important part of her legacy, although historians have debated exactly when her fortune crossed the million-dollar threshold and how the title should be defined.
What isn’t seriously disputed is the extraordinary scale of her accomplishment.
By the time of her death in 1919, Walker owned valuable real estate, operated a major national business and had accumulated substantial wealth at a time when Black Americans faced widespread discrimination, segregation and economic exclusion.
Her rise remains one of the most significant entrepreneurial achievements of the early 20th century.
Wealth With a Purpose
Walker believed success carried responsibilities.
She donated money to Black schools, churches, community organizations and charitable causes.
She supported the NAACP, the National Association of Colored Women and other organizations working to improve opportunities for African Americans.
Walker was also outspoken about racial violence.
Following the horrific East St. Louis racial violence of 1917, she became involved in efforts demanding federal action against lynching.
Her activism demonstrated that she viewed economic power as more than personal achievement.
It could also be a tool for social change.
Villa Lewaro
Walker’s success was perhaps most visibly represented by her magnificent estate in Irvington, New York.
Known as Villa Lewaro, the mansion was designed by pioneering Black architect Vertner Woodson Tandy.
Completed around 1918, the estate became a gathering place for prominent figures in Black politics, business and culture.
For Walker, the mansion also made a statement.
The daughter of formerly enslaved parents had become wealthy enough to build an extraordinary estate overlooking the Hudson River.
It was a visible challenge to the racial and gender assumptions of her era.
A Legacy Larger Than Hair Care
Madam C. J. Walker died on May 25, 1919, at only 51 years old.
But the business and economic network she created continued after her death.
Her daughter, A’Lelia Walker, became an important cultural figure during the Harlem Renaissance, using her wealth and social connections to support artists, writers and intellectuals.
More than a century later, Madam C. J. Walker’s influence can still be seen in beauty entrepreneurship, direct-sales businesses and the growing number of Black women building companies of their own.
Her story also provides an important reminder about innovation.
Innovation doesn’t always mean inventing a machine or discovering a scientific principle.
Sometimes innovation means recognizing an overlooked market, improving an existing idea, creating a better system and giving other people an opportunity to succeed along with you.
Why We Remember Madam C. J. Walker
Madam C. J. Walker began life as Sarah Breedlove, the daughter of formerly enslaved parents.
She was orphaned as a child.
She worked as a washerwoman.
She experienced poverty, discrimination and limited opportunities.
Yet she ultimately became a manufacturer, marketer, employer, philanthropist, activist and one of the most celebrated entrepreneurs of her generation.
Perhaps her greatest accomplishment wasn’t simply that she built an empire.
It was that she created a path for thousands of other women to build something of their own.
That’s why Madam C. J. Walker deserves to be remembered—and why her story belongs in Forgotten Genius Friday.
About Forgotten Genius Friday
Forgotten Genius Friday is an STM Daily News series highlighting inventors, innovators, entrepreneurs and overlooked historical figures whose ideas and achievements helped shape the world around us.
Know someone whose story deserves to be told? Leave a comment below, and subscribe to the STM Daily News newsletter so you don’t miss the next Forgotten Genius Friday.
Related Links
- National Women’s History Museum — Madam C. J. Walker Biography — A detailed overview of Walker’s rise from poverty, entrepreneurship, philanthropy, and civil-rights activism.
- Smithsonian National Portrait Gallery — Madam C. J. Walker — Features a historic circa-1914 portrait of Walker by photographer Addison N. Scurlock.
- Indiana Historical Society — Madam C. J. Walker — Explores Walker’s Indianapolis connection and points readers toward the extensive Madam C. J. Walker Family Archives.
- Indiana Historical Society — Madam C. J. Walker Digital Collection — A particularly valuable resource containing digitized photographs, business records, materials concerning Walker Agents, and documents from the Walker company.
- Smithsonian — Madam C. J. Walker Hair Product Tin — A fascinating look at an actual Walker hair-care product held by the Smithsonian and the history behind her beauty business.
Nature
What in the Heck Is a Sweat Bee? Turns Out, My Wife Wasn’t Making It Up
My wife Rebecca said she thought a sweat bee stung her. I thought she was making it up. Turns out, sweat bees are very real—and their strange name actually makes perfect sense.
It started with a conversation with my wife, Rebecca.
She mentioned that she thought she’d been stung by something called a “sweat bee.”
My immediate reaction was basically:
“What in the heck is a sweat bee?”
I’ll admit it. For a moment, I thought she was making the whole thing up. 😂
A sweat bee? Really?
It sounded like one of those names somebody invents when they don’t know what actually stung them.
“It wasn’t a regular bee. It was a… uh… sweat bee!”
So naturally, I asked ChatGPT the same question: What in the heck is a sweat bee?
Well, Rebecca gets this round.
Sweat bees are absolutely real.
And Yes, They’re Interested in Your Sweat
Sweat bees belong primarily to the Halictidae family, a large group of generally small bees found around the world.
Some are rather ordinary-looking little insects, while others are surprisingly flashy, sporting metallic shades of green, blue, bronze or gold.
But here’s where they earned that wonderfully unfortunate name.
Some sweat bees are attracted to human perspiration.
They’re not after you because they’re angry, and they’re certainly not tiny vampire bees. They’re interested in the salt and minerals in your sweat.
In other words, after you’ve been outside working, gardening, exercising or simply trying to survive a hot summer afternoon, a sweat bee may look at you and think:
“Hey! Free electrolytes!”
Wait…They Can Sting Too?
Unfortunately for Rebecca, there’s another part of her story that checks out.
Female sweat bees can sting.
They’re generally not aggressive and aren’t flying around looking for people to attack. But if one gets trapped against your skin, squeezed or swatted, it may defend itself.
Their sting is generally considered relatively mild compared with those of many other bees and wasps—but “relatively mild” probably isn’t much consolation when you’re the person who just got stung.
So, Rebecca, I officially withdraw my skepticism.
Mostly.
Don’t Declare War on Them
As annoying as having a tiny bee land on your sweaty arm might be, sweat bees are actually beneficial insects.
They’re important pollinators, visiting wildflowers, garden plants and agricultural crops and carrying pollen from flower to flower.
So if one lands on you, gently brushing or blowing it away is probably a better idea than swatting it against your skin.
And that’s today’s unexpected nature lesson.
Sweat bees are real.
They really are attracted to sweat.
The females really can sting.
And, perhaps most importantly…
My wife was right.
There. I said it.
I’m sure I’ll never hear the end of this one. 😂
Related Links
- University of Arizona Cooperative Extension — Arizona Bee Identification Guide — A useful Arizona-focused guide that includes sweat bees and explains their appearance, size, nesting behavior and attraction to salt in perspiration.
- USDA Natural Resources Conservation Service — Native Bees and Their Favorite Flowers — More information about native pollinators and the important role sweat bees play around wildflowers.
- USDA Forest Service — Bee Basics — A broader guide to North American bees, including the colorful metallic members of the sweat bee family.
- Smithsonian National Museum of Natural History — Sweat Bee — See an actual female sweat bee specimen (Augochlorella aurata) and its scientific classification.
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Forgotten Genius Fridays
Forgotten Genius Friday: Marian Croak — The Inventor Behind the Way We Communicate
Marian Croak helped pioneer the technology behind internet calling and text-to-donate fundraising. With more than 200 U.S. patents, her innovations have transformed how millions of people communicate, work, and give.
Last Updated on August 7, 2026 by Daily News Staff
Every day, billions of people make video calls, join virtual meetings, send text-message donations during disasters, and stay connected with loved ones over the internet.
Few realize that one of the pioneers behind these technologies is Marian Croak, an engineer, inventor, and technology leader whose work has fundamentally changed how the world communicates.
Despite holding more than 200 U.S. patents and helping shape modern internet communications, Croak remains largely unknown outside the technology community. That’s exactly why she deserves a place in our Forgotten Genius Fridayseries.
From Engineering to Innovation
Marian Rogers Croak earned a bachelor’s degree from Princeton University before completing a Ph.D. in Social Psychology and Quantitative Analysis at the University of Southern California.
Her unique combination of engineering expertise and an understanding of human behavior would become one of her greatest strengths. Rather than simply building technology, she focused on solving real-world communication problems.
She joined Bell Labs, later becoming part of AT&T, where she spent decades developing new telecommunications technologies.
Helping Create the Internet Calling Revolution
For much of the twentieth century, telephone calls relied on dedicated telephone lines.
Croak helped pioneer technologies that made Voice over Internet Protocol (VoIP) practical, allowing voice conversations to travel over internet networks instead.
Today, VoIP powers countless services, including:
- Zoom
- Microsoft Teams
- WhatsApp calling
- FaceTime
- Internet-based business phone systems
- Telemedicine appointments
Millions of remote workers, students, families, and businesses depend on technologies that evolved from these innovations.
A Better Way to Help During Disasters
One of Croak’s most visible inventions came from a simple but powerful idea.
What if people could donate to disaster relief simply by sending a text message?
She led the development of systems that made text-to-donate campaigns possible.
Following disasters such as Hurricane Katrina and the devastating 2010 Haiti earthquake, millions of people contributed to relief efforts simply by sending a short text message. The technology helped raise tens of millions of dollars quickly, demonstrating how communication technology could save lives beyond making phone calls.
More Than 200 Patents
Croak has been awarded more than 200 U.S. patents covering internet communications, networking, emergency response systems, and digital collaboration.
Her inventions have influenced everything from enterprise communications to cloud networking and mobile technologies.
Leading Responsible Artificial Intelligence
In 2014, Croak joined Google as a Vice President of Engineering.
Today, she helps lead initiatives focused on Responsible AI and Human-Centered Technology, working to ensure artificial intelligence benefits society while addressing issues of fairness, accessibility, and trust.
Her career reflects an important lesson: innovation is not just about building powerful technology—it is also about building technology responsibly.
Honors and Recognition
Although Marian Croak spent decades working behind the scenes, her achievements have earned growing recognition.
Among her honors are:
- National Inventors Hall of Fame inductee
- National Academy of Engineering member
- American Academy of Arts and Sciences fellow
- IEEE Founders Medal recipient
These awards recognize a lifetime devoted to improving how people connect with one another.
Why Marian Croak Matters
Many inventors create products.
Marian Croak created possibilities.
Every internet phone call between grandparents and grandchildren, every virtual doctor’s appointment, every online business meeting, and every text-message donation during a humanitarian crisis reflects technologies she helped make possible.
Her story reminds us that some of history’s greatest innovators work quietly behind the scenes, changing the world without becoming household names.
That’s exactly the kind of legacy Forgotten Genius Friday exists to celebrate.
Related Links
- National Inventors Hall of Fame – Marian Croak — An excellent overview of Croak’s career, her work advancing VoIP, text-to-donate technology, and her induction into the Hall of Fame.
Learn more about Marian Croak at the National Inventors Hall of Fame - National Inventors Hall of Fame – The Problem-Solving Engineer — A deeper profile examining Croak’s path from an inquisitive young student to a telecommunications pioneer.
Read Marian Croak: The Problem-Solving Engineer - Google – Marian Croak — Croak’s official Google author and leadership profile, including her work in Responsible AI and Human-Centered Technology.
Explore Marian Croak’s work at Google - Google – Marian Croak’s Vision for Responsible AI — An interview exploring how Croak brought her decades of technological experience into the development of responsible artificial intelligence.
Read about Marian Croak’s vision for Responsible AI - Princeton University – Marian Croak and Innovation — Princeton highlights Croak, a member of its Class of 1977, and her contributions to VoIP, innovation, mentorship, and women in STEM.
Read Princeton’s profile featuring Marian Croak
🧠 Discover the remarkable innovators, inventors, and trailblazers who helped shape our world but rarely receive the recognition they deserve. Share your thoughts in the comments and subscribe to the STM Daily News newsletter to catch every new Forgotten Genius Friday feature and more inspiring stories delivered to your inbox.
