HIV originated in Central and West Africa from a virus in chimpanzees

Wild chimpanzees have been spotted with leprosy lesions

In research published in 2021, scientists reported discovering cases of leprosy in wild chimpanzees from Guinea-Bissau and the Ivory Coast—marking the first time the disease has been found in any nonhuman species in Africa. They confirmed that leprosy was the cause of the deformities by testing the animals' poop for the presence of the disease-causing bacteria.

Chimpanzees are dying from human colds

For some great apes, the threat of human-borne diseases outweighs poaching or habitat loss. This article details the danger of reverse zoonoses, which refers to diseases that spread from humans to animals.

Watch how viruses like Ebola can spill over from animals to humans—and vice-versa

More than 70% of all new infectious diseases originate in animals. Referred to as zoonotic diseases, these are diseases that originate in animals and occasionally spill over or jump from animals to humans. Bats, mosquitoes, and primates have all been linked to spillover events. As human populations push further into previously uninhabited wilderness, animal-human contact increases, and disease spillover is inevitable.

Genetic analysis suggests Anopheles mosquitoes fed on humans some 1.8 million years ago

The 2026 paper, based on 11 species of Anopheles mosquitoes found in Southeast Asia, suggests that mosquitoes in the region likely developed their human blood preference between 2.9 million and 1.6 million years ago, overlapping with when scientists believe Homo erectus arrived there. (Some users may encounter a paywall.)

Where did zombies come from?

This 17-minute video dives into the origin of modern-day zombies. Zombies can be traced to early West African spiritual practices, specifically Vodou. Vodou evolved from the mixture of beliefs held by enslaved Africans in the French colony of...

Watch how viruses like Ebola can spill over from animals to humans—and vice-versa.

Up to 8% of the human genome consists of ancient viral DNA

Human endogenous retroviruses are remnants of infections that affected human primate ancestors millions of years ago and were passed on by infiltrating sperm and egg cells. Studies have shown that this DNA may play a role in immune responses and in placental formation.

Scientists have struggled to pin down Ebola's natural reservoir species for decades, but the available evidence suggests that it's very likely fruit and insect-eating bats found in Africa.

Where are humans on the evolutionary tree?

This interactive tree-shaped map explores the evolutionary connections between more than two million species. According to this map, humans are on the same branch as great apes, tarsiers, and treeshrews. That branch then splits into even smaller branches, with humans appearing on the same twig-like branch as chimpanzees and bonobos.

Ebola species have historically been named after where they were discovered, stigmatizing residents who live there, including Bundibugyo, in Uganda.

Humans may be the ultimate invasive species

Originating in East Africa, Homo sapiens migrated across the world beginning about 60,000 years ago and directly harmed countless species by consuming resources and modifying ecosystems to serve our needs. While meeting the definition of an invasive species, some ecologists argue the opposite, claiming that humans have helped preserve numerous species.

The Paranthropus genus, our mysterious extinct cousins

In the last century, skull and jaw fragments have been discovered in East Africa suggesting an ancient hominin species lived, evolved, and died alongside humanity's ancestors. With large, broad skulls and strong jaws, the Paranthropus genus—which includes several related species—is an absorbing case of the effects of niche partitioning, where species coexist by adapting differently to the environment. Paranthropus died out and human ancestors endured. Find out why here.

See how Ebola tore through Guinea, Sierra Leone, and Liberia in 2014-2016

Frontline traced how the outbreak started and spread across West Africa. documenting first-hand accounts and patient experiences. This Ebola outbreak was the deadliest to date, resulting in over 11,000 deaths.

Europe’s first recorded influenza pandemic swept the continent in 1580

The 1580 influenza pandemic, traced from Asia to Africa and into Europe, became the first flu outbreak clearly documented across the continent—killing tens of thousands and highlighting influenza’s potential for rapid global spread.

See the evolution of Ebola vaccine and treatment development.

The coronavirus likely came from China’s wet markets

A wet market is a type of marketplace primarily selling fresh, perishable goods such as meat, fish, and produce, often in a non-supermarket environment. The term originated in Singapore during the 1970s, and the "wet" aspect refers to the wet floors resulting from the washing of stalls and the use of ice to keep food fresh. Such markets have been identified as a major source of zoonotic outbreaks, including the COVID-19 pandemic.

West Nile is named after the district in Uganda where it was first isolated from a patient

In 1937, scientists isolated the virus from a woman in the West Nile District of Uganda. It's since been detected in much of Africa, Eastern Europe, West Asia, the Middle East, and was first detected in US patients during an outbreak in 1999.

Visualizing the genetics of SARS-CoV-2

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, began with an outbreak in Wuhan, China in December 2019, and rapidly spread worldwide in early 2020. On March 11, 2020, the World Health Organization declared COVID-19 a global pandemic, leading to widespread lockdowns, travel restrictions, and economic disruptions.

Measles evolved from an ancient cattle disease as early as 3,000 years ago

Genetic analysis suggests that the closest modern relative of measles is a livestock virus known as rinderpest, with the viral strains diverging between 2,000 and 3,000 years ago. The timing coincided with the rise of major cities above 250,000 people, offering a novel transmission route for the newly mutated measles virus.

The US military, concerned about potential deployments worldwide, has long funded experimental hantavirus vaccines and therapies.

Collaborations between the military, biotech, and academic researchers led to an experimental antibody treatment for the Andes hantavirus strain—the one that more readily passes between humans. As of spring 2026, it had only been tested in animals. The US Army has also tested a potential hantavirus vaccine in people. It published early findings in 2023 that seemed promising, eliciting some immune system response. (Some users may encounter a paywall.)

Watch the history of human migration that led to civilizations

Starting in Africa where they hunted with spears and fires, humans would gradually move out of the continent over thousands of years as they navigated crossing deserts, rivers, uneven terrain, and shifting climates. Development of technology, language, farming, and other societal structures helped build up the first civilizations.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

Evidence of cancer has been found in a 1.7-million-year-old fossil

Cancer has existed as long as humans have, with some of the earliest evidence found among fossilized bone tumors, human mummies in ancient Egypt, and ancient manuscripts. The oldest example was uncovered in a toe—millions of years old—from an ancestor of modern-day humans.

Genetic analysis indicates that every organism on Earth evolved from a single cell

LUCA—the last universal common ancestor—lived about 4.2 billion years ago and likely obtained energy through the conversion of carbon dioxide and hydrogen gas consumed from atmospheric gases at the ocean's surface or hydrothermal vents—openings on the seafloor where fluid warmed and enriched with minerals by Earth's interior is expelled.

Experimental hantavirus vaccines and therapies, still under development, have long been funded by the US military.

In 1892, two scientists purposefully infected themselves with cholera bacteria

When they became ill—one with mild diarrhea and the other with severe cholera—researchers pointed to that as proof that the pathogen caused the disease.

Children under 5 account for 76% of all malaria deaths in Africa

The main hypothesis for why the disease hits this age group the hardest is that children this young have still-developing immune systems. Pregnant women and people with HIV/AIDS are also at higher risk of severe infection.

Cryptococcus neoformans, a growing threat, causes infections in the brain and lungs

This inhalable, microscopic pathogen is found worldwide. It rarely causes illness, but it can take root in those with compromised immune systems, including people with advanced HIV/AIDS. Symptoms of cryptococcal infection—such as a stiff neck, vomiting, and confusion—can begin weeks or months after breathing in spores, though sometimes symptoms won’t appear for years. There are no known cases of transmission between people or between people and animals.

Cultural norms about how to handle the bodies of loved ones in communities in West Africa have hampered Ebola responses.

Post-WWII decolonization in Africa led to Cold War proxy conflicts

As newly independent African nations emerged after World War II, the US and USSR vied for influence—backing opposing sides in civil wars and revolutions. Conflicts in Angola, Ethiopia and Mozambique became proxy fronts in the Cold War.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

Great Zimbabwe: the massive medieval trading hub in southern Africa

Arising during the 13th century, the Kingdom of Zimbabwe’s capital quickly grew into a central trading hub, dealing in items from across the world, before its decline in the 1400s. Great Zimbabwe had three distinct districts, each surrounded by...

This real-time tracking of the hantavirus cruise ship outbreak in May 2026 offers a unique glimpse into the global reach of the outbreak and whether the virus sickened passengers and their communities around the world.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity, where it was purposefully grown in the English royal gardens at Kew, the Faculty of Medicine in Paris, and a few other locations.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.

In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

A small portion of The Winstons' 'Amen, Brother,' an obscure '60s gospel record, is the basis for thousands of hip-hop tracks, making it one of the most sampled records ever that's informally known as 'the Amen break.'

The name 'Silicon Valley' arose from the founding of Shockley Semiconductor Laboratory in Fairchild Semiconductor in 1956-57, founded near Stanford University in Palo Alto

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

Trace how the Bill of Rights, inspired by centuries of political theory, took shape between 1774 and 1789.

See 33 images that became central to huge scandals, including a young Charles and Camilla, Michael Jackson's baby on a hotel balcony, and Hugh Grant's mugshot.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.