These are the top 20 scientific discoveries of the decade

The 2010s yielded many incredible finds and important milestones. Here are our favourites.Saturday, 7 December 2019

Pluto's haze layer shows its blue colour in this picture taken by the New Horizons Ralph/Multispectral ...
Pluto's haze layer shows its blue colour in this picture taken by the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC). The high-altitude haze is thought to be similar in nature to that seen at Saturn’s moon Titan. The source of both hazes likely involves sunlight-initiated chemical reactions of nitrogen and methane, leading to relatively small, soot-like particles (called tholins) that grow as they settle toward the surface. This image was generated by software that combines information from blue, red and near-infrared images to replicate the colour a human eye would perceive as closely as possible.
Photograph by NASA/JHUAPL/SwRI

As the 2010s come to an end, we can look back on an era rife with discovery. In the past 10 years, scientists around the world made remarkable progress toward understanding the human body, our planet, and the cosmos that surrounds us. What’s more, science in the 2010s became more global and collaborative than ever before. These days, major breakthroughs are likelier to come from groups of 3,000 scientists than groups of three.

So much has happened, thanks to so many, that National Geographic’s writers and editors decided not to whittle down the last decade into just a handful of discoveries. Instead, we’ve put our heads together to identify 20 trends and milestones that we found especially noteworthy, and that we think will set the stage for more amazing finds in the decade to come.

Detecting the first gravitational waves

In 1916, Albert Einstein proposed that when objects with enough mass accelerate, they can sometimes create waves that move through the fabric of space and time like ripples on a pond’s surface. Though Einstein later doubted their existence, these spacetime wrinkles—called gravitational waves—are a key prediction of relativity, and the search for them captivated researchers for decades. Though compelling hints of the waves first emerged in the 1970s, nobody directly detected them until 2015, when the U.S.-based observatory LIGO felt the aftershock of a distant collision between two black holes. The discovery, announced in 2016, opened up a new way to “hear” the cosmos.

In 2017, LIGO and the European observatory Virgo felt another set of tremors, this time made when two ultra-dense objects called neutron stars collided. Telescopes around the world saw the related explosion, making the event the first ever observed in both light and gravitational waves. The landmark data have given scientists an unprecedented look at how gravity works and how elements such as gold and silver form.

Shaking up the human family tree

The decade has seen numerous advances in understanding our complex origin story, including new dates on known fossils, spectacularly complete fossil skulls, and the addition of multiple new branches. In 2010, National Geographic explorer-at-large Lee Berger unveiled a distant ancestor named Australopithecus sediba. Five years later, he announced that South Africa’s Cradle of Humankind cave system contained fossils of a new species: Homo naledi, a hominin whose “mosaic” anatomy resembles that of both modern humans and far more ancient cousins. A follow-up study also showed that H. naledi is surprisingly young, living at least between 236,000 and 335,000 years ago.

Other remarkable discoveries piled up in Asia. In 2010, a team announced that DNA pulled from an ancient Siberian pinky bone was unlike any modern human’s, the first evidence of a shadowy lineage now called the Denisovans. In 2018, a site in China yielded 2.1-million-year-old stone tools, confirming that toolmakers spread into Asia hundreds of thousands of years earlier than once thought. In 2019, researchers in the Philippines announced fossils of Homo luzonensis, a new type of hominin similar to Homo floresiensis, the “hobbit” of Flores. And newfound stone tools on Sulawesi predate modern humans’ arrival, which suggests the presence of a third, unidentified island hominin in Southeast Asia.

Revolutionising the study of ancient DNA

As DNA sequencing technologies have improved exponentially, the past decade has seen huge leaps in understanding how our genetic past shapes modern humans. In 2010, researchers published the first near-complete genome from an ancient Homo sapiens, kicking off a revolutionary decade in the study of our ancestors’ DNA. Since then, more than 3,000 ancient genomes have been sequenced, including the DNA of Naia, a girl who died in what is now Mexico 13,000 years ago. Her remains are among the oldest intact human skeletons ever found in the Americas. Also in 2010, researchers announced the first draft of a Neanderthal genome, providing the first solid genetic evidence that one to four percent of all modern non-Africans’ DNA comes from these close relatives.

In another striking discovery, scientists studying ancient DNA revealed in 2018 that a 90,000-year-old bone belonged to a teenage girl whose mother was Neanderthal and whose father was Denisovan, making her the first hybrid ancient human ever found. In another find, scientists compared Denisovan DNA to fossil proteins to confirm that Denisovans once lived in Tibet, expanding the mysterious group’s known range. As the field of ancient DNA has matured, so too has its handling of ethical concerns, such as the need for community engagement and the repatriation of indigenous human remains.

Revealing thousands of new exoplanets

Human knowledge of planets orbiting distant stars took a giant leap forward in the 2010s, in no small part thanks to NASA’s Kepler Space Telescope. From 2009 to 2018, Kepler alone found more than 2,700 confirmed exoplanets, more than half the current total. Among Kepler’s greatest hits: the first confirmed rocky exoplanet. Its successor TESS, launched in 2018, is starting its survey of the night sky and has already bagged 34 confirmed exoplanets.

Ground-based surveys were also in on the action. In 2017, researchers announced the discovery of TRAPPIST-1, a star system just 39 light-years away that hosts a whopping seven Earth-size planets, the most found around any star other than the sun. The year before, the Pale Red Dot project announced the discovery of Proxima b, an Earth-size planet that’s orbiting Proxima Centauri, the star closest to the sun at a mere 4.25 light-years away.

Entering the Crispr era

The 2010s marked huge advances in our ability to precisely edit DNA, in large part thanks to the identification of the Crispr-Cas9 system. Some bacteria naturally use Crispr-Cas9 as an immune system, since it lets them store snippets of viral DNA, recognise any future matching virus, and then cut the virus’s DNA to ribbons. In 2012, researchers proposed that Crispr-Cas9 could be used as a powerful genetic editing tool, since it precisely cuts DNA in ways that scientists can easily customise. Within months, other teams confirmed that the technique worked on human DNA. Ever since, labs all over the world have raced to identify similar systems, to modify Crispr-Cas9 to make it even more precise, and to experiment with its applications in agriculture and medicine.

While Crispr-Cas9’s possible benefits are huge, the ethical quandaries it poses are also staggering. To the horror of the global medical community, Chinese researcher He Jiankui announced in 2018 the birth of two girls whose genomes he had edited with Crispr, the first humans born with heritable edits to their DNA. The announcement sparked calls for a global moratorium on heritable “germline” edits in humans.

Seeing the cosmos as never before

The 2010s brought with them several major observations that are revolutionising our study of the universe. In 2013, the European Space Agency launched Gaia, a spacecraft that is collecting distance measurements for more than a billion stars in the Milky Way, as well as velocity data for more than 150 million stars. The dataset helped scientists make a 3D movie of our home galaxy, yielding an unprecedented look at how galaxies form and change over time.

In 2018, scientists released the final version of the Planck satellite’s measurements of the early universe’s faint afterglow, which contains vital clues to cosmic ingredients, structure, and rate of expansion. Puzzlingly, the expansion rate Planck saw differs from today’s, a potential "crisis in cosmology" that may require new physics to explain. Also in 2018, the massive Dark Energy Survey released its first batch of data, which will help with searches for hidden patterns in our universe’s structure. And in April 2019, scientists with the Event Horizon Telescope revealed the first-ever image of a black hole’s silhouette, thanks to a massive global effort to peer into the heart of the galaxy M87.

Unveiling ancient art

Discoveries from around the world have reinforced that art—or at least doodling—was an older and more global phenomenon that once thought. In 2014, researchers showed that hand stencils and a “pig-deer” painting in Sulawesi’s Maros cave sites were at least 39,000 years old, making them as old as Europe’s most ancient cave paintings. Then, in 2018, researchers announced the discovery of cave art in Borneo that’s between 40,000 and 52,000 years old, further pushing back the origins of figurative painting. And another 2018 find in South Africa, a stone flake that was cross-hatched some 73,000 years ago, may well be the world’s oldest doodle.

Other controversial finds stoked debate over Neanderthals’ artistic skills. In 2018, researchers unveiled pigments and perforated marine shells found in Spain that were 115,000 years old, when only Neanderthals lived in Europe. That same year, another study claimed that some of Spain’s cave paintings are 65,000 years old. Many cave-art specialists have disputed the find, but if it holds, it could be the first evidence of Neanderthal cave paintings. And in 2016, researchers announced that a French cave contained bizarre circles of stalagmites set up about 176,000 years ago. If cave bears didn’t somehow make them, the circles’ age suggests yet more Neanderthal handiwork.

Making interstellar firsts

Future historians might look back on the 2010s as the interstellar decade: For the first time, our spacecraft punctured the veil between the sun and interstellar space, and we got our first visits from objects that formed around distant stars.

In August 2012, NASA’s Voyager 1 probe crossed the outer boundary of the heliosphere, the bubble of charged particles our sun gives off. Voyager 2 joined its twin in the interstellar medium in November 2018 and captured groundbreaking data along the way. But the interstellar road is a two-way street. In October 2017, astronomers found ‘Oumuamua, the first object ever detected that formed in another star system and passed through ours. In August 2019, amateur astronomer Gennady Borisov found the second such interstellar interloper, a highly active comet that now bears his name.

Opening doors to ancient civilisations

Archaeologists made many extraordinary discoveries in the 2010s. In 2013, British researchers finally found the body of King Richard III—beneath what’s now a car park. In 2014, researchers announced that Peru’s Castillo de Huarmey temple complex still had an untouched royal tomb. In 2016, archaeologists revealed the first Philistine cemetery, offering an unprecedented window into the lives of the Hebrew Bible’s most notorious, enigmatic people. The following year, researchers announced that Jerusalem's Church of the Holy Sepulchre dates back more than 1,700 years to Rome's first Christian emperor, appearing to confirm that it's built on the site identified by Rome as the burial place of Christ. And in 2018, teams working in Peru announced the largest mass child sacrifice site ever uncovered, while other scientists scouring Guatemala detected more than 60,000 newly identified ancient Maya buildings with airborne lasers.

Big archaeological discoveries also surfaced from deep underwater. In 2014, a Canadian team finally found the H.M.S. Erebus, an ill-fated Arctic research vessel that sank in 1846. Two years later, another expedition located its sister ship, the H.M.S. Terror. In 2017, an effort led by Microsoft co-founder Paul Allen found the long-lost U.S.S. Indianapolis, which sank in 1945 and became one of the deadliest disasters in U.S. naval history. The Black Sea Maritime Archaeology Project has found more than 60 historic shipwrecks at the bottom of the Black Sea—including a pristine 2,400-year-old vessel discovered in 2018. And in 2019, Alabama officials announced the discovery of the long-lost Clotilda, the last ship that ferried enslaved Africans to the United States.

Breaking new ground in the solar system

In July 2015, NASA’s New Horizons probe made good on a decades-long quest to visit the icy world Pluto, sending back the first-ever images of the dwarf planet’s shockingly varied surface. And on New Year’s Day 2019, New Horizons pulled off the most distant flyby ever attempted when it snapped the first pictures of the icy body Arrokoth, a primordial leftover from the solar system’s infancy.

A little closer to home, NASA’s Dawn spacecraft arrived at Vesta, the second-biggest body in the asteroid belt, in 2011. After mapping that world, Dawn darted off to orbit the dwarf planet Ceres, the asteroid belt’s largest object—becoming the first mission ever to orbit a dwarf planet, and the first to orbit two different extraterrestrial bodies. Near the decade’s end, NASA’s OSIRIS-REx and JAXA’s Hayabusa2 visited the asteroids Bennu and Ryugu, respectively, with the goal of returning samples back to Earth.

Changing the course of disease

In response to the 2014-2016 Ebola outbreak in West Africa, public health officials and the pharmaceutical company Merck fast-tracked rVSV-ZEBOV, an experimental Ebola vaccine. After a highly successful field trial in 2015, European officials approved the vaccine in 2019—a milestone in the fight against the deadly disease. Several landmark studies also opened new avenues to preventing the spread of HIV. A 2011 trial showed that preventatively taking antiretroviral drugs greatly reduced the spread of HIV among heterosexual couples, a finding confirmed in follow-up studies that included same-sex couples.

Pushing reproductive limits

In 2016, clinicians announced the birth of a “three-parent baby” grown from the father’s sperm, the mother’s cell nucleus, and a third donor’s egg that had its nucleus removed. The therapy—which remains ethically controversial—aims to correct for disorders in the mother’s mitochondria. One 2018 study made precursors of human sperm or eggs out of reprogrammed skin and blood cells, while another showed that gene editing could let two same-sex mice conceive pups. And in 2018, Chinese scientists announced the birth of two cloned macaques, the first time that a primate had ever been cloned like Dolly the sheep. Though researchers avow that the technique won’t be used on humans, it’s possible that it could work with other primates, including us.

Tracking down the Higgs boson

How does matter get mass? In the 1960s and 1970s, physicists including Peter Higgs and François Englert proposed a solution in the form of a novel energy field that permeates the universe, now called the Higgs field. This theorised field also came with its associated fundamental particle, what’s now called the Higgs boson. In July 2012, a decades-long search ended when two teams at CERN’s Large Hadron Collider announced the detection of the Higgs boson. The discovery filled in the last missing piece of the Standard Model, the spectacularly successful—albeit incomplete—theory that describes three of the four fundamental forces in physics and all known elementary particles.

Rewriting paleontology textbooks

This decade has seen an explosion in our understanding of prehistoric life, as scientists have found stunning new fossils while expanding their analytical toolkits. In 2010, researchers supported by the National Geographic Society published the first full-body colour reconstruction for a dinosaur, based on the discovery of fossilised pigments. In the years since, the palette has widened, as paleontologists have found dino-camouflage, feathers that ranged from black to blue to iridescent rainbow, and reddish skin on one of the best-ever fossils of an armoured dinosaur. And in a remarkable feat of chemical sleuthing, researchers analyzed preserved fatty molecules and proved in 2018 that Dickinsonia, a primitive creature that lived more than 540 million years ago, was an animal.

In 2014, palaeontologists also revealed new fossils of the predatory dinosaur Spinosaurus that suggested it was a semiaquatic predator—the first known among dino-kind. A year later, a team in China unveiled the stunning fossil of Yi qi, a truly weird feathered dinosaur with membraned wings like a bat’s. Also in the last decade, scientists’ interest in Myanmar’s 99-million-year-old amber has surged, revealing a feathered dinosaur tail, a primitive baby bird, and all sorts of invertebrates trapped in the fossilised tree resin.

Finding life’s building blocks on other worlds

In the last 10 years, space missions have given us a more sophisticated look at other worlds’ carbon-based organic molecules, which are necessary ingredients for life as we know it. The European Space Agency’s Rosetta mission orbited and landed on Comet 67P Churyumov–Gerasimenko. The data it collected between 2014 and 2016 gave us an astonishingly close look at the raw materials that ancient impacts might have brought to Earth. Before NASA’s Cassini probe died in 2017, it confirmed that the watery plumes of Saturn’s moon Enceladus contain large organic molecules, a clue that it has the right stuff for life. And in 2018, NASA announced that its Curiosity rover had found organic compounds on Mars, as well as a bizarre seasonal cycle in the red planet’s atmospheric methane levels.

Ringing climate alarms louder than ever

Throughout this decade, atmospheric carbon dioxide were reaching levels that are unprecedented in modern times, with record temperatures to match. On May 9, 2013, global CO2 levels reached 400 parts per million for the first time in human history, and by 2016, CO2 levels were staying firmly above this threshold. As a result, the whole world felt an uptick in warming; 2015, 2016, 2017, 2018, and 2019 were the five hottest years on record since 1880. Starting in 2014, warming oceans kicked off a global coral bleaching event. Corals around the world suffered die-offs, including parts of the Great Barrier Reef. In 2019, Australia declared the island-dwelling Bramble Cay melomys extinct from sea level rise, the first known mammal lost to modern climate change.

In a series of major reports, the world’s scientists forcefully called attention to Earth’s altered climate, the risks it poses, and the need to respond. In 2014, the Intergovernmental Panel on Climate Change released its fifth assessment of climate change’s reality and consequences, and a year later, the world’s nations negotiated the Paris Agreement, the global climate accord that aims to keep warming below 2 degrees Celsius—which world leaders and scientists consider a dangerous threshold. In October 2018, the IPCC published another grim report that outlined the huge costs of warming even 1.5 degrees Celsius by 2100—which is likely the minimum the planet will face. In the face of such huge challenges, record-breaking climate protests have swept the world, many led by youth activists.

Discovering—and rediscovering—species

Modern biologists are identifying new species at a blistering pace, naming 18,000 new species a year on average. In the past decade, scientists described several charismatic mammal species for the first time, such as the Myanmar snub-nosed monkey, the Vangunu giant rat, and the olinguito, the first newfound carnivore in the Western Hemisphere since the late 1970s. The ranks of other animals groups also swelled, as scientists described newfound fish with “hands,” tiny frogs smaller than a dime, a giant Florida salamander, and many others. In addition, some animals, such as Vietnam’s saola and China’s Ili pika, were spotted once again after having gone missing for years.

But along with these many finds, scientists have tallied the exponential rate of modern extinctions. In 2019, scientists warned that a quarter of plant and animal groups are threatened with extinction, suggesting that as many as a million species—both known and unknown to science—are now at risk of dying out, some within decades.

Kicking off a new spaceflight era

The 2010s were a pivotal transition period for spaceflight, as access to low-Earth orbit and beyond became a more global—and commercial—enterprise. In 2011, China launched its first space laboratory, Tiangong-1, into orbit. In 2014, India’s Mars Orbiter Mission arrived at the red planet, making India the first country ever to successfully arrive at Mars on its first try. In 2019, Israeli nonprofit SpaceIL attempted the first privately funded lunar landing, and China’s Chang’e-4 mission performed the first soft landing on the lunar farside. The global astronaut corps also grew more diverse: Tim Peake became the first professional British astronaut, Aidyn Aimbetov became the first post-Soviet Kazakh cosmonaut, and the United Arab Emirates and Denmark sent their first astronauts to space. What’s more, NASA astronauts Jessica Meir and Christina Koch performed the first all-female spacewalk.

In the U.S., after the last space shuttle mission launched in 2011, private companies angled to fill the void. In 2012, SpaceX launched the first commercial resupply mission to the ISS, and in 2015, Blue Origin and SpaceX became the first companies to successfully launch reusable rockets to space and then vertically land them back on Earth, a milestone for cheaper launches to low-Earth orbit.

Seeing animals’ unexpected sides

The past decade has revealed unusual traits and behaviours across the animal kingdom. In 2015, National Geographic explorer David Gruber found that hawksbill sea turtles fluoresce green and red—the first biofluorescence ever recorded in a reptile. In 2016, researchers showed that the Greenland shark can live at least 272 years, making it the longest-lived vertebrate yet known. Our understanding of animal tool use also improved: One 2019 study showed for the first time that Visayan warty pigs use tools, and several studies showed that Brazil’s capuchins have been using tools for at least 3,000 years, the oldest such non-human record found outside Africa. In an extremely rare 2018 sighting, biologists in Kenya scientifically documented a black leopard in Africa for the first time since 1909.

Redefining the units of science

To understand the natural world, scientists must measure it—but how do we define our units? Over the decades, scientists have gradually redefined classic units in terms of universal constants, such as using the speed of light to help define the length of a meter. But the scientific unit of mass, the kilogram, remained pegged to “Le Grand K,” a metallic cylinder stored at a facility in France. If that ingot’s mass varied for whatever reason, scientists would have to recalibrate their instruments. No more: In 2019, scientists agreed to adopt a new kilogram definition based on a fundamental factor in physics called Planck’s constant and the improved definitions for the units of electrical current, temperature, and the number of particles in a given substance. For the first time ever, all our scientific units now stem from universal constants—ensuring a more accurate era of measurement.