Nobel Prize in Chemistry Is Awarded to 3 Scientists for Using Evolution in Design of Molecules

The 2018 Nobel Prize in Chemistry was awarded to Frances H. Arnold, George P. Smith and Gregory P. Winter for their work in evolutionary science.


Three scientists shared this year’s Nobel Prize in Chemistry for tapping the power of evolutionary biology to design molecules with a range of practical uses. Those include new drugs, more efficient and less toxic reactions in the manufacture of chemicals and plant-derived fuels to replace oil, gas and coal extracted from the ground.

Half of the prize and the accompanying $1 million went to Frances H. Arnold, a professor of chemical engineering at the California Institute of Technology. She is only the fifth woman to win a chemistry Nobel and the first since 2009.

The other half of the prize is shared by George P. Smith, an emeritus professor of biological sciences at the University of Missouri, and Gregory P. Winter, a biochemist at the M.R.C. Laboratory of Molecular Biology in England.

Dr. Arnold conducted the first directed evolution of enzymes, proteins that catalyze chemical reactions. Dr. Smith developed a method, known as phage display, in which a virus that infects bacteria can be used to evolve new proteins. Dr. Winter has used phage display to produce new pharmaceuticals.

The Royal Swedish Academy of Sciences said the scientists had managed to harness the power of evolution in test tubes. Enzymes produced through directed evolution are used to manufacture everything from biofuels to medical treatments. Phage display has produced antibodies that can neutralize toxins, counteract autoimmune diseases and even cure metastatic cancer.

“This year’s Nobel Laureates in chemistry have been inspired by the power of evolution and used the same principles — genetic change and selection — to develop proteins that solve mankind’s chemical problems,” the academy said in documents explaining the prizes.

Dr. Arnold’s work, which has been utilized to create sustainable biofuels, is “contributing to a greener world,” the academy added.

Dr. Smith’s development of phage display to link proteins to genes was described by the academy as “brilliant in its simplicity.” Dr. Winter was one of the leaders in using phage display to develop new biomolecules, including disease-blocking antibodies.

Evolution Saves Species From ‘Kill the Winner’ Disasters

Modelers find evidence that a combination of competition, predation and evolution will push ecosystems toward species diversity anywhere in the universe.

Ecologists have puzzled over how the various plankton that compete for the same resources in marine ecosystems can have such enduring diversity.

At a meeting of the American Society of Naturalists in 1960, the noted British ecologist G. Evelyn Hutchinson posed what he called “the paradox of the plankton.” Look at a flask of seawater; it will be filled with diverse species of plankton, all competing for the same vital elements and nutrients. Yet natural selection implies that over time, only one species should occupy an ecological niche, a concept known as competitive exclusion. And what is true of plankton seems to be true of many protozoa, plants, birds, fish and other organisms, too. How can ecosystems routinely have so many competing species that stably coexist?

Ecologists have mulled over this vexing paradox ever since, but they have generally taken comfort in a solution known as the “kill the winner” (KTW) hypothesis. It hinges on the predator-prey relationships in ecosystems, which are often species specific. As one species starts forcing out its competitors, its rising population allows more of its predators to prosper, too. Predation eventually pushes the number of prey back down again (hence, kill the winners). The combination of competition and predation then lets several populations of rival species coexist in equilibrium. The KTW hypothesis became many ecologists’ go-to explanation for biodiversity.

When Nigel Goldenfeld, the director of the NASA Astrobiology Institute for Universal Biology, and Chi Xue, a graduate student in his laboratory at the Carl R. Woese Institute for Genomic Biology, started looking more closely at the KTW idea in 2015, they didn’t intend to blow it up. Rather, they were exploring what features of life and ecosystems might be ubiquitous throughout the cosmos. Diversity seemed like a good candidate. “If you look at different isolated ecosystems on Earth, you see diversity everywhere,” Xue said. They were curious about what might create and sustain that diversity, and whether it might be as relevant on another planet.

But they noticed an unrealistic defect in the calculations that had traditionally been used in models to validate the KTW idea: They “described populations as if individuals did not exist. It’s as if we described a liquid without acknowledging atoms,” Goldenfeld explained by email. Because those models allowed populations to rebound even after plummeting to mere fractions of individuals, they underestimated the amount of extinction that could occur. (Goldenfeld and Xue refer to this problem as a lack of “stochastic noise” because the calculations do not reflect the mathematically arbitrary discontinuities that the real world’s limitations impose.)

Xue and Goldenfeld decided to redo the models more realistically. “We didn’t expect the KTW idea to fail,” Xue said. “We just wanted to see if there would be anything different if we added the noise.”

The results, which they recently described in Physical Review Letters, were catastrophic. Biodiversity and species coexistence didn’t just drop; they disappeared. “Basically, every species went to extinction,” Xue said. In repeated trials, fluctuating prey populations kept dropping to zero, and then their predators went extinct from lack of food. Sometimes the system devolved to a single pair of predator and prey species that persisted, but even those arrangements were not always stable. The kind of species-rich diversity found in nature was nowhere to be seen.



But Xue and Goldenfeld then went a step further to include something else that earlier simulations had left out: evolution. They allowed prey species to get better at evading predators, and predators to get better at catching prey.

What followed was an arms race, as the escalating capabilities of the prey and the predators evolved in parallel, and it made all the difference. That competition added more species diversity to the system while the KTW effects kept any one species from taking over. Biodiversity in the simulations flourished.

Xue and Goldenfeld see evidence from genomics that this coevolving dynamic occurs in nature, too. “When you look at bacteria and find the regions of the genome that are evolving faster, those are the regions involved with viral resistance,” Xue said. As their coevolving KTW model suggests, selection pressure to resist viruses seems to exceed other pressures — for example, to compete better against other bacteria.


Lucy Reading-Ikkanda/Quanta Magazine

Still, that’s not conclusive proof, and the researchers plan to investigate further how generalizable their conclusions are. They want to see what happens when predators are less specific about their prey. Another consideration, according to Goldenfeld, is that in addition to killing bacteria and other cells, viruses sometimes swap genes among them. This dual role — “as predator and also taxi driver for genes,” he said — can have profound effects on the evolution and stability of ecosystems.

It’s also uncertain whether the coevolving KTW model applies equally well to all types of life. “In principle, this interaction between predator and prey isn’t specific to microorganisms. It’s everywhere, like between the hare and fox,” Xue said. But she also noted that their model assumes that evolutionary changes (like mutations) and ecological changes (like the birth and death of organisms) happen on the same timescale and with about the same frequency. “That’s not really the case for species like the fox and hare, but that’s common in microorganisms.”

According to Jed Fuhrman, a professor of biological sciences at the University of Southern California, modeling approaches can generally be useful but should be interpreted cautiously. “Some assumptions and aspects are more directly applicable to complex natural systems than others.” Because even microbial communities employ a variety of survival strategies, he said, “models may apply to a portion of the community more than to others.”

But if the coevolving KTW model does prove to be broadly applicable, then according to Goldenfeld, it shows that “there are very generic ways to get diverse populations in an ecosystem and that monocultures are the exception, not the rule.” Wherever life evolves, even on other planets and moons, we should expect it to diversify into complex ecosystems. He said that one future direction for his lab’s work will be on “how a community metabolism emerges” from diverse organisms, each processing materials in their shared environment in different ways.

That idea could be relevant to space scientists, for example, when they send future probes to seek signs of life in the oceans under the ice covering Jupiter’s moon Europa and Saturn’s moon Enceladus. If life is there, they should probably expect to see the biochemical signatures of an entire ecosystem, not single organisms.

According to Kevin Peter Hand, a deputy project scientist for NASA’s Jet Propulsion Laboratory, the instrumentation being developed for probes to Mars, Europa, Enceladus and other suspected havens for life already look for signs broadly associated with ecosystems. He said that the proposed Europa Lander mission concept on which he is working is designed to capture “at least nine different, highly complementary measurements that are agnostic to individual biological species,” such as the complexity and chirality of any organic compounds and the presence of cell-like structures in samples.

But if astrobiologists ever get to move past the problem of whether life exists and can progress to examining how closely the dynamics of alien ecosystems resemble those of Earth, then knowing a solution to the paradox of the plankton may be critical.

Everything We Learned in One Year About Thousands of Years of Human Evolution

If you were to encounter humans from 300,000 years ago, you might be struck by how much they look like humans in 2018. Anatomically modern and large-brained, with faces and teeth not dissimilar to our own, these early Homo sapienswent to war, formed relationships, and created tools, just like us. There’s still plenty to learn about our direct evolutionary ancestors, but this year, thanks to the widespread use of genomic sequencing, scientists gave us an unprecedented glimpse into how humans came to be. Here, Inverse lists everything we’ve learned about human evolution in the past year.

While we are the only hominids to walk the Earth today, this year genomic evidence proved that the DNA of some people contains traces of Paleolithic trysts between humans and other Homo species, like the Neanderthals and the Denisovans. A decade ago, scientists would have been extremely skeptical. University of Buffalo evolutionary anthropologist Omer Gokcumen, Ph.D. tells Inverse that it’s only in the past five years that scientists have been able to confirm that early Sapiens didn’t only hang out with other Sapiens.

“You can think of the world 100,000 years ago like a Lord of the Rings world, where different, pretty smart human-like creatures are roaming,” Gokcumen says, explaining that this situation is called interaction dynamism. “One of them would be our ancestors in Africa, but there would also be other species like Neanderthals, that we could tell were different — but not different enough to not interbreed and produce fertile offspring.”

This year, academics including Gokcumen published an extensive amount of research filling in the details of this Tolkien-esque world, furthering our understanding of how our minds, bodies, and behavior came to be. Learning what it means to be human, it seems, means learning about really old humans.

1. Ancient Spit Reveals Mysterious Human ‘Ghost’ Ancestor

In July, Gokcumen and a team of scientists announced in Molecular Biology and Evolution that a protein in the saliva of people from sub-Saharan Africa indicates that they carry genetic evidence of an unknown hominin ancestor. The saliva protein became a point of interest when University of Buffalo oral biologist and co-author Stefan Ruhl, Ph.D. compared the saliva proteins of primates and humans. Typically, these proteins look very similar. That’s why it was startling when they discovered that one protein from the sub-Saharan African population was revealed to be very different in size than the others.

This protein, known as MUC7, is thought to be the result of genetic material left over from mating between Homo sapiens and a ‘ghost’ species as recently as 150,000 years ago. Gokcumen believes this mysterious species was confined to Africa and split from Homo sapiens’ evolutionary path around three million years ago. This study is further proof that we, in Gokcumen’s polite words, “absorbed different populations that lived around us” — mating with other Homo species, many of which are still unidentified.

“Our study adds to this generally more colorful picture of human history, and it’s becoming very clear that it’s not as simple as we previously thought,” says Gokcumen. “It’s become very clear to researchers that even though the majority of our genome can be traced back to particular, Homo sapien ancestral population, there’s observable evidence that other, smaller populations made their way into our modern human gene pool.”

Read more: Humans Had Sex with Ancient ‘Ghost’ Species, Spit Analysis Shows

2. Newly Discovered Fossils Pushed Back Our Origins by 100,000 Years

Scientists announced a textbook-changing discovery in June, writing in Nature that they discovered three Homo sapiensfossils that date back to approximately 300,000 years ago. Previously, the oldest Homo sapiens found were 200,000 years old. These fossils were excavated in Jebel Irhoud, Morocco, contradicting the popular claim that our species evolved from a “cradle of mankind” in East Africa.

“The dating was a bit, wow!” co-author Jean-Jacques Hublin, Ph.D., said in his interview with Inverse in June. “No one imagined these remains could be that old. In the meantime, the interpretation of the fossil evidence suddenly made much more sense.”

Read more: Discovery Puts First Humans in North Africa 300,000 Years Ago

A facial reconstruction of one of the ancient samples found in Morocco. 

3. Neanderthal Genes Responsible for Bad Habits and Modern-Day Looks

Research published in October by scientists from the Max Planck Institute for Evolutionary Biology added further detail to what we know about the Neanderthal genes some humans carry around today. In the American Journal of Human Genetics, the team explained that Neanderthal DNA strongly influences the hair and skin color of the one to five percent of European and Asian people who carry this DNA. Neanderthal alleles also shape whether people have lighter and darker skin tones and determine hair color, indicating that ancient hominids had many different hair and skin colors, too.

Drawing from a sample of 112,000 study participants, the scientists additionally determined that there was a significant link between people who carry Neanderthal DNA and those who had experienced “loneliness of isolation, frequency of enthusiasm or disinterest in the last two weeks, and smoking status.”

Read more: Blame Neanderthal Genes for Your Bad Habits and Good Looks

4. The Remains of One of the Oldest Americans Were Found in Mexico

Human remains found in 2012 in Mexico’s Tulum system of submerged caves were re-analyzed this year, leading scientists to believe the remains are the oldest osteological remains of humans in the Americas. In a paper published in PLOS One in August, the scientists behind the research, led by Heidelberg University paleoecologist Wolfgang Stinnesbeck, Ph.D., explain the bones likely belong to a young man who lived around 13,000 years ago.

Stinnesbeck and his team dated one bone, the pelvis, by measuring the levels of uranium, carbon, and oxygen isotopes within it as well as that within the stalagmite that had grown through it. Calcite layers, which contain oxygen and carbon isotopes, store information about climate and precipitation data, which helps determine an age.

The researchers claim this discovery adds further proof to the theory that humans came to the Americas at least 5,000 years before the Clovis, a prehistoric group of people who have previously been called the first Americans.

Read more: A Stolen Human Skeleton Found in 2012 Might Be Americas’ Oldest

5. Neanderthal Brains Grew At a Slower Pace Than Human Brains

In a paper published in Science in September, an international team of scientists reported that they found 13 ancient Neanderthal skeletons in a 49,000-year old cave in northern Spain. To the astonishment of the researchers, one of the specimens, which they named El Sidron, was a nearly complete specimen that belonged to a boy who died when he was almost eight years old.

El Sidron’s teeth and endocranial features suggested that his brain growth wasn’t done by the time of his death, giving away his age. A human brain is essentially grown to its full size by the time a person is six, but El Sidron’s brain was still growing at a period when the brains of his peers had long since stopped. This extended period of brain growth, the study authors hypothesize, suggest Neanderthal children spent more time acquiring cognitive skills than human children.

But perhaps the most marvelous revelation from this study was the fact that, barring brain growth, Neanderthal children were much like human children in terms of physical growth and maturation, reducing the gap between us and our not-so-distant cousins.

Read more: Ancient Child’s Skeleton Unlocks Secret About Modern Brain Development

Comparison of modern human and Neanderthal skulls.

6. Some of Man’s Earliest Ancestors Were Furry Rat-Like Creatures

If you imagine your ancient human ancestors, you might an envision a bulky, strong caveperson, ready to hunt and provide. But if you look past that ancestor and deeper into their lineage, you’d see a something that looks a lot like a rat.

In November, scientists reported in Acta Palaeontologica Polonica that they excavated two fossilized teeth belonging to this rat-like creature in the rocky cliffs of Dorset, England. The teeth are believed to be 145 million years old, and the scientists claim they are the oldest evidence of this human ancestor ever found. The claim is contested by a different team of scientists, who say theirfinding is the oldest at 160 million years old, but their study’s validity is still being debated.

The nocturnal, placental mammal is thought to be an ancestor of mice, pygmy shrews, blue whales and elephants — putting us humans in good company within the animal kingdom.

7. Human Speech Is Our Evolutionary Advantage Over Monkeys

In a very Planet of the Apes-like turn of events, scientists announced in July that the reason that monkeys can’t talk like humans isn’t because of their vocal anatomy but their neural wiring. In a Science study led by the University of Vienna’s W. Tecumseh Fitch, Ph.D., scientists used x-ray videos to examine the vocal tracts of living macaques while they ate, made facial displays, and vocalized monkey sounds. Analysis revealed that their vocal tracts could “easily produce an adequate range of speech sounds to support spoken language,” disproving previous theories that both human anatomy and the human brain give us our specialized ability to speak.

Instead, Fitch argues that the “evolution of human speech capabilities required neural changes rather than modifications of vocal anatomy.” This revelation likely offers a clue to a bigger mystery: Understanding why human language emerged in the first place. Maybe we’ll find that out this year.

The 25 Biggest Scientific Breakthroughs of 2017

Every week in 2017 seemed to bring new, objectively bad news about environmental degradation, government officials being awful, or video gamesbeing ruined by microtransactions. But it wasn’t all bad news: Very exciting and groundbreaking research was added to the scientific literature this year, reminding us that not everything is moving backward.

The 25 studies below, representing the biggest breakthroughs of the year, represent a wide and eclectic range of research areas. Let these snippets from Inverse’s interviews with researchers offer a sense of just how many scientific fields strode forward in 2017:

  • “It’s a terrible way to define different populations,” a geneticist studying skin color said.
  • “Best-case scenario, some of the advertising is true. Worst-case scenario: very little to none of the advertising is true and people may actually get hurt,” said a psychologist about the problems with mindfulness.
  • “What we showed is that diarrhea is actually really good for you,” said a scientist researching diarrhea.

Without further ado, here are the studies that rocked the science world this year, presented in order of popularity among our readers, though not necessarily importance:

25. Neanderthals Never Would Have Outlived Us

Humans still contain a small percentage of Neanderthal DNA. Even though we know that humans and Neanderthals overlapped for about 15,000 years, scientists aren’t sure how our ancient cousins died out. They’re pretty sure that Neanderthals would have been replaced by humans no matter what. Computer modeling shows that humans migrating out of Africa would have replaced Neanderthals, whether or not they died out from other factors. But while they lived together, Neanderthals left their genetic legacy imprinted in our DNA.

24. Magic Mushrooms Can Help with Depression

Scientists put tripping patients into fMRI machines to observe what their brains did under the influence of psilocybin, the active ingredient in hallucinogenic, “magic,” mushrooms. They found that patients with depression described feeling “reset” after a trip, and brain scans supported this conclusion. Patients who reported feeling better also showed reduced blood flow to parts of the brain associated with depressive symptoms.

23. Teeth From 9.7 Million Years Ago Could Rewrite Human History

Scientists found teeth in Germany that they suspect come from hominins. They date back to before similar human ancestors arose in Africa, suggesting that we may need to rework the entire human evolutionary timeline. Whether it’s a product of convergent evolution or simply related species, these fossils raise more questions about human origins than they answer.

22. Eating Weed and Spicy Food Is Good for Your Gut

More good news from 2017! Researchers found that marijuana and spicy food can ease inflammation in your digestive system, potentially paving the way for new treatments for Type 1 diabetes, colitis, and other gut issues. Capsaicin, the spicy stuff in chili peppers, makes your digestive system produce a type of cannabinoid that can offer protective benefits to your gastrointestinal tract, suggesting that edible marijuana could do the same thing. This is good news for lovers of spicy food and edibles.

21. Dogs Are Genetically Predisposed to Being Good Boys

It’s not all bad news for 2017: Scientists examining dog genetics found that dog genes predispose them to domestication and prosocial behavior. This study is the first to show why, on a molecular level, dogs are _so good). Interestingly, the scientists also found that the same genetic changes that led to domestication also seems to have made dogs less intelligent than wolves.

20. You’re More Likely to View Atheists as Serial Killers

Even though atheism has become more common in modern society, it turns out believing in something might make you seem less like a psychopath, according to a study published this year. People are more likely to believe that a killer in a hypothetical scenario is an atheist instead of a person of faith, according to research published this year. This finding even held true for atheists, perhaps suggesting some internalized stigma leading to unconscious bias. Even Mark Zuckerberg has taken note of this anti-atheist prejudice, announcing his faith a year ago.

19. Human-Pig Chimeras Have a “Safety Switch”

Scientists shocked the world when they announced they’d developed a human-pig chimera, bringing us a step closer to growing human organs inside pigs. But they also soothed our fears of a pig-man apocalypse when they assured us that there is a self-destruct mechanism for human stem cells that accidentally travel to the pig brains. It’s not even clear whether that would lead to enhanced consciousness, but if this safety switch works, we won’t have to worry about it.

18. Psychologists are Growing Skeptical of Mindfulness Practices

Mindfulness has become a pop psychology buzzword recently, and psychology professionals are concerned. Fifteen psychologists published a paper this year outlining their concerns that corporate seminars, meditation workshops, and the like are offering psychological benefits that are unproven while ignoring risks. After all, psychological health is not one-size-fits-all.

17. Even Occasional Drinks Can Affect Your Brain Health

We all know that drinking too much can cause chronic health problems, but a massive cohort study of British civil servants found that moderate drinking accelerates cognitive decline. Over 30 years of surveys and health check-ups, the participants who consumed 14 to 21 units of alcohol per week “had three times the odds of right sided hippocampal atrophy,” an early warning sign of Alzheimer’s disease. This is a serious buzzkill, since previous research has suggested that moderate drinking could have certain benefits for heart health. Following this cohort of research subjects further will reveal more about their health as they age.

16. Your Face Shows Signs of Class Boundaries

It’s sometimes easy to tell whether someone is wealthy based on their clothes, car, home, and other material things. But this year researchers found that social status may show in your face, too. This doesn’t mean that some people are genetically predisposed to be rich, but rather that being poor can impart subtle, lifelong mood symptoms that observers can see on your face even when you’re wearing a neutral expression. Worryingly, the researchers found that this judgment can impair hireability, which could perpetuate class boundaries.

15. Scientists Identified the Maximum Human Lifespan

Life extension advocates like to say that, with the right supplements and therapies, you’ll be able to live long enough to see science bring about immortality. But more conventional-thinking researchers say this isn’t so. They identified the maximum human lifespan as 115.7 years for women and 114.1 years for men. This area of research is still hotly debated, but the new findings fit pretty closely to what other groups have said.

14. A Supervolcano Could Go Off Way Sooner Than We Think

As if 2017 wasn’t bad enough, statisticians say we’re overdue for a supervolcano eruption. On the basis of geological records, a team of researchers estimated that cataclysmic supervolcano eruptions on Earth occur, on average, every 17,000 years. The last one happened 20 to 30 thousand years ago. You do the math.

13. Geneticists Discovered That Light Skin Variations Originated in Africa

Science has often been used in the service of justifying racism, but scientists shut down outdated notions of genetic differences among humans of different ethnic groups this year. Geneticists found that variants associated with light skin actually originated in Africa, not only disproving the backward notion that people with darker skin are less human, but also calling into question the notion that skin color can be associated with certain ethnic groups.

12. Scientists Find the Oldest Human Skeleton in the Americas

After re-examining a skeleton stolen from a submerged cave in Mexico, scientists determined that it may represent the oldest human remains ever found in the Americas. At 13,000 years old, the 80-percent-complete skeleton suggests that humans came to the Americas thousands of years before the people that were previously thought to be the first Americans.

11. Diarrhea Is Your Body’s Immune System Savior

Diarrhea sucks, but there’s actually a good reason for it. Mice infected with a mouse bacteria similar to E. coli exhibited changes in intestinal cells in a way that seemed to cause diarrhea. Scientists have long suspected that diarrhea was the body’s way of clearing out disease, but this study provided the first solid proof.

10. Redditors’ Dicks Match Up With Dick Size Desires

Many penis-havers worry about whether their penis size will match up with the preferences of penis-likers. In a study conducted by and among redditors, they found that penis sizes matched up pretty well with what their potential partners want. These findings fit with what academic researchers have found, but maybe this citizen science confirmation will be more digestible for redditors.

9. Porn Can Change Your Brain

People who watch a lot of pornography don’t necessarily have an addiction or a psychological condition. But neuroscientists have found that people who struggle with their porn use exhibit brain changes. They react more strongly to reward cues associated with porn, similar in some ways to gambling addicts. It’s not clear whether porn addiction is a real condition, though.

8. Scientists Send Data to and from Space Using Quantum Entanglement

Scientists in China transmitted a quantum state almost a thousand miles into space, much farther than had been done previously. This development brought scientists one step closer to the kind of technology that could enable quantum computing. Quantum entanglement is a burgeoning topic in physics that even Albert Einstein didn’t believe could exist.

7. Human Mini-Brain Organoids Raise Ethical Concerns

Scientists can grow miniature models of human organs, called organoids that allow them to perform research that would be unethical on living. But when scientists reported that human brain organoids grafted onto rat brains had begun to integrate, this raised ethical red flags. If a rat has a partially human brain, should we be doing science on it that we wouldn’t do on a human?

Alex Jones

6. Conspiracy Theorists Think Differently

European social psychologists have shed some light on what makes the nearly half of American conspiracy theorists different from the rest. They exhibit a phenomenon called illusory pattern perception, which makes them see patterns of danger where there is no danger. This is the first scientific evidence linking illusory pattern perception to belief in conspiracy theories.

5. Ancient Humans Knew How to Avoid Incest

We know that incest increases the chances of developing genetic diseases, but it turns out our early human ancestors knew about the risks of incest, too. Geneticists and archaeologists examining 34,000-year-old human remains from Russia found that four people buried together were no closer than second cousins, suggesting that even ancient humans made efforts to avoid inbreeding. Researchers say this probably means these early humans made a purposeful effort to mix outside their family groups, including some semblance of romance, as indicated by the jewelry included in their collective burial.

4. Scientists Discovered Our Black Hole Neighbors

Astronomers using NASA’s NuSTAR X-ray telescope found evidence of two super-massive black holes. At the center of galaxies near the Milky Way, they’re still millions of light-years away, but in relative terms, they’re our next-door neighbors.

3. Long-Term Marijuana Use Changes Your Brain

Marijuana is safe, as far as drugs go, but that doesn’t mean it’s totally free of long-term consequences. In a mouse study, neuroscientists found that long-term marijuana use can lead to abnormally high dopamine levels. This suggests that marijuana could be messing with your brain chemistry more than you thought.

2. Scientists Figured Out That Tattoo Ink Doesn’t Stay Put

That’s right, even though the whole idea of a tattoo is that the ink goes into your skin and never comes out, researchers have found that ink pigment nanoparticles migrate and accumulate in people’s lymph nodes. It makes sense since your lymphatic system gets rid of bad stuff and tattoo ink is essentially a foreign invader.

The 25 Most-Read Inverse Science Stories of 2017: Wild, Wonderful & Strange

This year will be remembered for its immense cultural and social upheavals, both good and unbelievably, Earth-shatteringly bad. But what appears to have remained consistent, at least judging by the science stories that Inverse fans read, interacted with, and shared, is a healthy curiosity about the the weird and wonderful, the science of our own bodies and minds, and scientific discoveries that push the limits of what we currently consider reality. That, and an obsession with whatever Neil deGrasse Tyson has to say about anything.

To celebrate a strange and sensational year in science, here are the 25 science stories that Inverse readers loved the most.

A Hamer individual from Ethiopia who took part in the study. Many alleles associated with light skin originated in Africa, not in Europe.

25. Genetics Researchers Just Disproved a Long-Held Racist Assumption

As racial tensions escalated this year in America and around the world, scientists found hard evidence that many of the assumptions people make about people with dark skin are completely, utterly unfounded. Many people still act as if people born with dark skin are less human, a behavior inherited from Middle-Age Europeans who believed the African people they encountered were not the same species as them. In October, scientists revealed they — and the people who continue to promote those beliefs — were completely wrong, showing that the human genes for dark and light skin all originated in Africa.

Read more about the racist theory debunked by science.

24. Drake Equation Revision Hugely Ups Odds of Intelligent Alien Life

The Drake Equation, written in 1961 for the first meeting of SETI (Search for Extraterrestrial Intelligence), is a seven-variable equation that calculates the odds that there are any active civilizations beyond Earth. In 2016, scientists decided it was a bit outdated, and so they updated it to include new data on exoplanets collected in the 50+ years since the equation was written. The new probability that there isn’t any other intelligent life out there is 10 billion trillion — making it extremely likely that there is something else out there.

Read more about your chances of meeting aliens in this lifetime.

23. Science Explains the Marijuana Hangover

The marijuana hangover — replete with headache, fatigue, fogginess, and dehydration, — has long confused pot users, who are more likely to associate the symptoms with alcohol. Scientists chalk the tired feeling up to the restless sleep that ensues when you get too high, and the dehydration you feel is caused by weed shutting down saliva production, which is what also causes the dreaded “dry mouth” while smoking.

Read more about the psychological and physical downside of a pot brownie binge.

22. Humans Have Been Having the Same Nightmare for Thousands of Years

Over the centuries, humans have come up with countless, often absurd, explanations for the phenomenon known as sleep paralysis. When it strikes, sleepers find themselves suddenly awake but unable to move, pinned to their bed as if a heavy weight is sitting on their chest. Scientists think the phenomenon has its roots in our brains, which actively paralyze us during REM sleep so that we don’t act out our dreams. If we’re suddenly interrupted during that phase, our brains sometimes “wake up” before our bodies do, leading to the terrifying nightmare-like experience.

Read more about sleep paralysis, which led to the evolution of the “Night Hag”.

Fossils found in submerged tunnels in Mexico might be the oldest human artifacts found in the Americas.

21. A Stolen Human Skeleton Might Be America’s Oldest

An investigation of the spoils from a plundered underwater cave in Tulum, Mexico, turned up an unlikely guest: the most ancient human skeleton ever found in the Americas. The Chan Hol II skeleton, which was first discovered in February 2012 and was actually stolen shortly after photos of it went public, was recovered by scientists who showed, using carbon dating, that it was 13,000 years old.

Read more about the very first Americans, who were actually in Mexico.

20. Diarrhea Is Evolution’s Immune System Drain-O

Poop will never not be funny for readers. It’ll also never not be interesting to scientists. This June, they discovered that diarrhea serves a critical purpose for animals, having evolved over millennia of evolution. As much as it sucks to get the runs while traveling or after eating an adventurous meal, having to rush to the can is much better than not getting diarrhea. The uncomfortable bowel movement, the scientists reported, is your body’s way of flushing out all of the potentially life-threatening toxins in your gut before they get into the rest of your body.

Read more about the biological reason diarrhea is good for you.

19. 20 Years After the Great Lego Spill, They’re Still Washing Ashore

In 1997, a container ship called the Tokio Express bound for New York was hit by a wave so huge that it knocked an enormous container full of 4.8 million pieces of Lego into the water. While at the time it didn’t seem like the miniature blocks would ever make it to their final destination, in July of this year residents of Cornwall, United Kingdom reported that the pieces are still washing up on the beach, suggesting there’s still a chance they may float to the other side of the Atlantic.

Read more about Lego pieces posing a hazard to barefoot British beach-goers.

18. Reddit Study on Ideal Penis Size Consistent With Dick Science

Despite all the changes that took place this year, our fascination with penis size did not waver. In July, the results of a small Reddit survey on penis size were presented in graph form, showing an upside-down U-shaped curve spanning lengths from four to ten inches. While this survey only incorporated self-reported data from 761 users, the results actually matched up well with what scientists already know about average peen size: like Reddit’s dicks, most dongs are about six and seven inches long and five to six inches around.

Read more about the average penis size and girth, on Reddit and elsewhere.

17. Neuroscience Reveals How the Brain Changes as it Watches Porn

We’re watching porn at record-breaking rates, and all that visual, er, stimulation has scientists wondering what it’s doing to us on an individual and a societal level. So far, we’ve learned that porn acts in many ways like a drug, causing our brains to release the pleasure-tr iggering neurotransmitter dopamine, and it may also activate the amygdala, the part of the brain linked to emotional behavior and motivation. Word’s still out on whether casual porn watching is problematic, but some scientists worry that very frequent porn viewing might be linked to certain psychological issues.

Read more about what all those late-night Pornhub visits do to your brain cells.

16. The Real Story Behind ‘Roanoke’ Is Creepier Than ‘AHS’

The sixth season of American Horror Story, centered on the historical real-life tragedy of the lost American colony at Roanoke, premiered in 2016, but it continued to intrigue Inverse readers well into 2017. Scientists have used lasers, magnometers, and radar to uncover rare objects that survived the 400 years since the colony was founded, but these still haven’t cleared up whether the colonists succumbed to disease, a violent uprising, or something even more sinister.

Read more about American Horror Story and the even more horrific Roanoke legend behind it.

15. China Transmits Data Into Space Using Quantum Entanglement

Around the world, scientists are making huge leaps in the field of quantum teleportation, which could revolutionize quantum computer security. China’s researchers are leading the pack, this year succeeding in transporting a quantum particle 870 miles into space — breaking the former distance record of 62 miles.

Read more about China’s supremacy in the quantum teleportation race.

14. Human Mini-Brains Growing Inside Rat Bodies Are Integrating

We’re living in the age of farmed organs, but scientists are still working out the kinks. These days, they’re growing human mini-organs inside animal bodies using stem cells that can be coerced into turning into livers, hearts, and brains. The brains are proving to be a bit problematic: in November, scientists reported that human brain cells grown inside rats are starting to transfer blood and nerve signals, giving the researchers pause: might these rat-brain hybrids become conscious?

Read more about whether hybrid rat-human brains will ever wake up.

13. Conspiracy Theorists Have a Basic Cognitive Issue, Say Scientists

Conspiracy theories abounded this year, which is perhaps not surprising, as previous studies have shown that increases in such beliefs tend to correlate with rising mistrust in authority structures. In October, scientists discovered what’s different about the way that people with these beliefs actually think: people who tend to believe in conspiracy theories, they explained, see patterns that don’t actually exist, and it’s this “illusory pattern perception” that causes them to believe in bizarre explanations for those imaginary patterns.

Read more about what’s different about the brains of conspiracy theorists.

12. Here’s Scientist Bill Richards’s Playlist for Tripping on Mushrooms

Psychedelic researchers have had a big year, using mind-altering drugs to treat psychological illness and thereby mitigating decades of stigma against them. Studies on the effects of the drugs, however, must be meticulously designed so that they will be considered legitimate, and so Bill Richards, Ph.D., a Johns Hopkins University researcher, used science to create a seven-hour playlist to maximize the experience of a psychedelic trip.

Read more about how to listen to music during a mushroom trip like a psychedelic scientist.

11. The Crazy Flat Earthers’ Theory That Trees Don’t Exist Isn’t Completely Crazy

The Flat Earth Movement drew criticism from Bill Nye, Neil deGrasse Tyson, and pretty much every other rational mind out there, but one of their bizarre theories actually kind of made sense. Kind of. Some Flat Earthers believe that what we call trees are actually just the tiny remnants of a world where trees were as wide as mountains and were so tall they scraped the sky. In the “no forests” theory, the present-day world represents the sad, small remains of what the Earth once was — which, as Inverse argued, is not altogether untrue.

Read more about the flat-Earther “no forest” theory and its somewhat compelling argument.

10. Indonesia Sea Monster Has Been Identified (It’s Not a Giant Squid)

In May, our appetite for the grotesque was satiated when news broke about a “sea monster” that had washed up on the shore of Indonesia’s Maluku Islands. This 50-foot-long blob of flesh was so badly decomposed that it was unidentifiable, and the giant bones that pierced through it only deepened its mystery. But about a week after it washed up, experts finally determined that it was the corpse of a type of baleen whale, misshapen because of the hot gases that bloated up inside it during decomposition.

Read more about the huge, dead sea animals mistaken for sea monsters.

9. Genetic Analysis Shows Early Humans Avoided Inbreeding, Incest

This year marked the penultimate season of Game of Thrones, which was as rife with incestuous themes as any other season. A study published in October echoed those themes, suggesting that our ancient human ancestors were a lot less genetically reckless than the inhabitants of Westeros. In the Science study, archaeologists showed evidence that humans buried together in Russia 34,000 years ago were no closer than second cousins, suggesting that even these humans knew not to bone their closest relations.

Read more about why incest is best left to the characters on Game of Thrones.

8. Scientists Discover Super-Massive Black Holes Just Outside Our Own Galaxy

We’re comfortable making movies about black holes because they’ve long seemed so far removed from real life, but a study published in January suggested that they’re a lot closer to us than we think. In an announcement from NASA’s Jet Propulsion Laboratory, scientists reported that they’d found evidence of two super-massive black holes in two of the Milky Way’s neighboring galaxies, 39 million and 176 million light years away from us.

Read more about your friendly neighborhood super-massive black holes.

7. Long-Term Marijuana Use Changes Brain at the Cellular Level, say Scientists

Weed smokers have long noticed, anecdotally, that long-term marijuana use tends to change people’s behavior, but it wasn’t until October of this year that scientists started to notice the cellular changes underlying those behavioral shifts. Using rats that were administered daily doses of marijuana, researchers publishing in JNeurosci showed that the GABA neurons in the brain were unable to properly regulate the amount of dopamine swimming around, causing abnormally drawn-out good feelings of reward — which is the mechanism that’s thought to lead to addiction.

Read more about marijuana’s long-term effects on your brain.

6. Upper Body Strength Is Biggest Factor in Male Attractiveness

Scientists behind a controversial study, published in December, used the results of a questionably designed experiment to argue that women, by and large, find strong-looking men attractive because those men look like they can fight. The ability to fight, in turn, is said to be appealing because ancient women needed men to protect them, and some vestige of that preference remains today. The researchers’ explanation, however, didn’t take into account the fact that perhaps the women involved in the study were not necessarily hard-wired to find those men attractive and rather were subject to a number of other influences, including their own personal choice.

Read more about why male attractiveness isn’t all about being swole.

5. Neil deGrasse Tyson Slams Flat Earth Theory With a Single Picture

Astrophysicist and notorious know-it-all Neil deGrasse Tyson could not resist sharing his thoughts on the rising Flat Earth conspiracy theorist movement, tweeting a sick eclipse-related riddle in November that was guaranteed to stump even the staunchest “globalist” truther.

Read more about Neil deGrasse Tyson’s admittedly clever addition to the flat Earth debate.

4. What Never Leaving Your Hometown Does to Your Brain

Written in 2015, this scientific investigation on the psychological effect of staying in one’s hometown remains a perpetual Inverse Science favorite. It’s not surprising, considering that migration rates among American youth are at a historic low and that more and more people are choosing to put down roots in the states where they were born.

Read more about the psychological effect of never leaving home.

3. Nanoparticle Scientists Warn Tattooed Folks: Ink Doesn’t Stay Put

A report from nanoparticle scientists in September, published in Scientific Reports, cast doubt on the permanence of ink tattoos, revealing that tiny particles from certain kinds of inks actually swim away from the skin and wind up in the lymph nodes. In particular, they found elevated levels of titanium dioxide, a white compound that’s often added to other pigments, in the lymph nodes of the four cadavers they used in their small study. It’s not clear yet whether the escaped compounds pose any danger to people with tattoos, but it’s certainly something scientists must consider.

Read more about the troubling impermanence of seemingly “permament” tattoos.

2. Surgeons Remove Over 28 Pounds of Feces From a Constipated Man

It was hard for readers to resist the horrific photo of an enormous colon, clogged with nearly 29 pounds of feces, cradled like a small animal in the arms of a surgeon. It belonged to a 22-year-old Chinese man in Shanghai who, suffering from an ailment called Hirschsprung’s disease, was unable to expel the majority of waste in his body for his entire life. He’s fine now, thanks to a team of surgeons who removed 30 inches of his swollen colon during a 3-hour operation.

Read more about what happens to a body when it never gets to poop.

1. Scientists Have Found the ‘Holy Grail’ of Physics, Metallic Hydrogen

Kicking off the year, in January, was a monumental announcement by Harvard physicist Isaac Silvera, Ph.D., who claimed to have created metallic hydrogen — a theoretical state of matter that scientists never thought would be possible. Silvera reported in Science that he had forced elemental hydrogen into that state using immense amounts of pressure and extremely cold temperatures, noting that, if produced in large enough amounts, metallic hydrogen could be used as a form of fuel for deep space travel. Other scientists in the narrow field, however, did not mince words when the time came to publicly criticize Silvera’s work.

Eating Green Could Be in Your Genes

Could there be a vegetarian gene?

global frequency pattern of an allele adaptive to vegetarian diets

Cornell University researchers describe a genetic variation that has evolved in populations that have historically favored vegetarian diets, such as in India, Africa, and parts of East Asia.

A different version of this gene (called an allele) adapted to a marine diet was discovered among the Inuit in Greenland, who mainly consume seafood.

The vegetarian allele evolved in populations that have eaten a plant-based diet over hundreds of generations. The adaptation allows these people to efficiently process omega-3 and omega-6 fatty acids and convert them into compounds essential for early brain development and controlling inflammation. In populations that live on plant-based diets, this genetic variation provided an advantage and was positively selected in those groups.

In Inuit populations of Greenland, the researchers uncovered that a previously identified adaptation is opposite to the one found in long-standing vegetarian populations: While the vegetarian allele has an insertion of 22 bases (a base is a building block of DNA) within the gene, this insertion was found to be deleted in the seafood allele.

“The opposite allele is likely driving adaptation in Inuit,” said Kaixiong Ye, co-lead author of the paper appearing Mar. 29 in the journal Molecular Biology and Evolution. Ye is a postdoctoral researcher in the lab of Alon Keinan, associate professor of biological statistics and computational biology, and the paper’s co-senior author.

“Our study is the first to connect an insertion allele with vegetarian diets, and the deletion allele with a marine diet,” Ye said.

“It is the most interesting example of local adaptation that I have been fortunate to help study,” said Keinan. “Several studies have pointed to adaptation in this region of the genome. Our analyses combine to show that the adaptation is driven by an insertion of a small piece of DNA that we know its function. Moreover, when it reached the Greenlandic Inuit, with their marine-based diet rich in omega-3, it might have become detrimental.”

FADS1 and FADS2 are enzymes that are essential for converting omega-3 and omega-6 fatty acids into downstream products needed for brain development and controlling inflammation. Meat and seafood eaters have less need for increased FADS1 and FADS2 enzymes to get proper nutrition because their omega-3 and omega-6 fatty acid conversion process is simpler and requires fewer steps.

This study is based on previous work by co-senior author Tom Brenna, professor of human nutrition and of chemistry, who showed the insertion can regulate the expression of FADS1 and FADS2 and hypothesized it could be an adaptation in vegetarian populations.

Ye, Keinan and colleagues analyzed frequencies of the vegetarian allele in 234 primarily vegetarian Indians and 311 U.S. individuals and found the vegetarian allele in 68 percent of the Indians and in just 18 percent of Americans. Analysis using data from the 1,000 Genomes Project similarly found the vegetarian allele in 70 percent of South Asians, 53 percent of Africans, 29 percent of East Asians and 17 percent of Europeans.

“Northern Europeans have a long history of drinking milk and they absorbed enough end products from milk for long-chain fatty acid metabolism so they don’t have to increase capacity to synthesize those fatty acids from precursors,” said Ye.

“One implication from our study is that we can use this genomic information to try to tailor our diet so it is matched to our genome, which is called personalized nutrition,” he added.

The researchers are not sure yet when the adaptation first occurred, as analyses of chimpanzee or orangutan genomes did not uncover the vegetarian allele. But there is evidence for the allele in early hominid Neanderthal and Denisovan genomes.

“It is possible that in the history of human evolution, when people migrated to different environments, sometimes they ate a plant-based diet and sometimes they ate a marine-based diet, and in different time periods these different alleles were adaptive,” meaning the alleles have a tendency to evolve under dietary pressures, Ye said.

Chicken study reveals evolution can happen much faster than thought: New study of chickens overturns popular assumption that evolution is only visible over long time scales — ScienceDaily

Scientists found two mutations that had occurred in the mitochondrial genomes of the birds in only 50 years, showing a rate of evolution much higher than the widely accepted rate of change in the mitochondrial genome of about 2 percent per million years.

A selective mating approach within the population that started in 1957 has resulted in an over tenfold difference in the size of the chickens.

A new study of chickens overturns the popular assumption that evolution is only visible over long time scales. By studying individual chickens that were part of a long-term pedigree, the scientists led by Professor Greger Larson at Oxford University’s Research Laboratory for Archaeology, found two mutations that had occurred in the mitochondrial genomes of the birds in only 50 years. For a long time scientists have believed that the rate of change in the mitochondrial genome was never faster than about 2% per million years. The identification of these mutations shows that the rate of evolution in this pedigree is in fact 15 times faster. In addition, by determining the genetic sequences along the pedigree, the team also discovered a single instance of mitochondrial DNA being passed down from a father.

This is a surprising discovery, showing that so-called ‘paternal leakage’ is not as rare as previously believed. The study is published in the online early version of the journal, Biology Letters.

Using a well-documented 50-year pedigree of a population of White Plymouth Rock chickens developed at Virginia Tech by Professor Paul Siegel, the researchers reconstructed how the mitochondrial DNA passed from mothers to daughters within the population. They did this by analysing DNA from the blood samples of 12 chickens of the same generation using the most distantly related maternal lines, knowing that the base population had started from seven partially inbred lines. A selective mating approach within the population started in 1957, resulting in what is now an over tenfold difference in the size of the chickens in the two groups when weighed at 56 days old.

Senior author Professor Larson said: ‘Our observations reveal that evolution is always moving quickly but we tend not to see it because we typically measure it over longer time periods. Our study shows that evolution can move much faster in the short term than we had believed from fossil-based estimates. Previously, estimates put the rate of change in a mitochondrial genome at about 2% per million years. At this pace, we should not have been able to spot a single mutation in just 50 years, but in fact we spotted two.’

The paper says there is now considerable evidence of a disparity between long-term and short-term estimates of mitochondrial changes. One theory put forward in recent studies is that mitochondrial DNA evolves ‘non-neutrally’, that there is a purifying selection process and negative mutations are removed more quickly, resulting in the impression of a short-term elevation in rates. There have been few studies of short-term mitochondrial evolution, including both mutation rates and paternal leakage. There is now direct evidence that it is not always inherited from the mother.

Study lead author Dr Michelle Alexander, from the University of York, said: ‘The one thing everyone knew about mitochondria is that it is almost exclusively passed down the maternal line, but we identified chicks who inherited their mitochondria from their father, meaning so-called ‘paternal leakage’ can happen in avian populations. Both of these findings demonstrate the speed and dynamism of evolution when observed over short time periods.’

Fish contain genetic blueprint for limbs

Think of a world populated only by giant insects on land, and fishes in water. According to Joost Woltering of University of Geneva, that is what Earth would look like if the transition from fins to limbs had not happened.  In a study published this week in PLoS Biology, Woltering and colleagues have found some definitive clues about this transition. By studying a group of ‘architect’ genes present in both fish and mammals — the Hox genes — the scientists were able to find out that the DNA structure and regulatory mechanism for limb and digit formation were present in fish even before the transition happened, but the enhancements required to activate digit formation evolved only in tetrapods (ie. four-legged land animals).

The role of Hox genes in limb and fin formation is crucial. Malfunctioning Hox genes result in animals missing large segments of their limbs. Mammalian Hox genes have an interesting feature. “In the forming limbs the HoxA and HoxD genes are switched on in two independent ‘waves’ the first making the proximal limb (arm/leg) and the second making the digits (toes/fingers),” said Woltering in an email to this correspondent.

Limb formation in tetrapods is usually attributed to this ‘bimodal’ behaviour of Hox genes. So the scientists were surprised to observe the same mechanism in Hox genes in zebrafish fin radials (the bony part at the end of fins), too. So are the two structures ancestrally the same or “homologous” structures?

To test this, the team inserted fish Hox genes into mouse embryos and found that in the resulting mice, Hox genes were active only in the proximal part of the limbs, not in the digits. “This showed that the fish counterpart of the mouse ‘digit’ domain cannot yet ‘make’ digits,” said Woltering. Therefore fish fin radials and tetrapod digits are not “homologous” in the classical sense.

However, keeping in mind the shared regulatory mechanism in Hox genes of fish and those of mice, the team propose the re-definition of “homology.” “For instance, there are genes that are expressed in the hand and in hair follicles, this fact doesn’t make them homologous structures,” he said. “Only if the underlying ‘switches’ that determine where a gene is expressed are homologous, the structures are homologous.”

Dr. Arkhat Abzhanov, an evolutionary biologist from Harvard University who was not involved in the study, agrees. “Identical expression patterns of the same gene(s) could in principle be established by non-homologous regulatory mechanisms so it might be very helpful to look at the regulatory details,” he said in an email.

Charles Darwin to receive apology from the Church of England for rejecting evolution.

The Church of England is to apologise to Charles Darwin for its initial rejection of his theories, nearly 150 years after he published his most famous work.

The Church of England will concede in a statement that it was over-defensive and over-emotional in dismissing Darwin’s ideas. It will call “anti-evolutionary fervour” an “indictment” on the Church”.

Charles Darwin to receive apology from the Church of England for rejecting evolution

The bold move is certain to dismay sections of the Church that believe in creationism and regard Darwin’s views as directly opposed to traditional Christian teaching.

The apology, which has been written by the Rev Dr Malcolm Brown, the Church’s director of mission and public affairs, says that Christians, in their response to Darwin’s theory of natural selection, repeated the mistakes they made in doubting Galileo’s astronomy in the 17th century.

“The statement will read: Charles Darwin: 200 years from your birth, the Church of England owes you an apology for misunderstanding you and, by getting our first reaction wrong, encouraging others to misunderstand you still. We try to practise the old virtues of ‘faith seeking understanding’ and hope that makes some amends.”

Opposition to evolutionary theories is still “a litmus test of faithfulness” for some Christian movements, the Church will admit. It will say that such attitudes owe much to a fear of perceived threats to Christianity.

Cosmic rays zap a planet’s chances for life.

Mysterious cosmic rays constantly bombard Earth from outer space. Now scientists find these energetic particles could limit where life as we know it might exist on alien planets. Cosmic rays continue to baffle scientists more than a century after they were first discovered. These charged subatomic particles zip through space at nearly the speed of light, a few strangely with energies up to 100 million times beyond what is possible from the most powerful particle accelerator on Earth. Cosmic rays are believed to be atomic nuclei, with the vast majority being protons, or hydrogen nuclei.

When hit Earth’s atmosphere, they generate a shower of other particles, including muons, which are essentially much heavier versions of their cousin the electron. Some of these particles reach Earth’s surface, potentially damaging on land and in the oceans—muons can even penetrate hundreds of feet below a planet’s surface.

Scientists investigated how cosmic rays might influence the habitability of distant alien worlds. The hundreds of exoplanets astronomers have discovered in the past two decades using ground and space telescopes have raised the possibility that some might be home to extraterrestrial life. Interest is especially focused on worlds in so-called habitable or Goldilocks zones, which receive enough heat to possess surfaces that can keep water liquid rather than freeze—on Earth, there is life virtually wherever there is liquid water.

The investigators reasoned the level of radiation a planet receives helps control its habitability. While a planet might see much fewer compared to the radiation from its star, the average energy of cosmic rays is far higher than photons and protons from the star, making them critical to focus on.

“If the radiation dose is too high, then life as we know it cannot exist,” said study author Dimitra Atri, a physicist at the Blue Marble Space Institute of Science, a nonprofit institute with a network of scientists across the world.

The researchers concentrated on two factors that might influence the cosmic ray dose a planet gets—the strength of its , and the depth of its atmosphere.

“I started thinking about this problem when I was thinking about Mars and Earth, which are next-door neighbors, and how we have a thriving biosphere here on Earth, while it’s safe to say Mars does not have a thriving biosphere on its surface. Why is that so?” Atri said. “The main factor is that Mars has a high level of radiation—the atmosphere on Mars is almost negligible, very, very small compared to Earth’s, and it has no planetary magnetic field, so it has no shielding from the cosmic rays found everywhere in the galaxy. So I wondered what intermediate scenarios might be like, lying between these two extremes.”

The investigators simulated planets ranging from ones with no magnetic field to ones as strong as Earth’s, and worlds with atmospheres ranging from as thick as Earth’s to just a tenth as thick.

“We know the magnetic field around Earth protects us from these harmful cosmic rays, and we thought magnetic fields were going to be the main factor that controls the radiation dose to the surface,” Atri said.

Unexpectedly, “we found the thickness of a planet’s atmosphere is a much more important factor in determining a planet’s radiation dose,” Atri told Astrobiology Magazine. “If you took the Earth and you completely removed the magnetic field, the radiation dose rate will increase by two, which is a big increase, but it would still have very small effects, and would not have any effects on us. However, if you keep the magnetic field and decreased the atmosphere so it is a tenth as thick, the will increase by more than two orders of magnitude.”

Planets around red dwarf stars are often thought of as prime targets for the search of alien life, since these relatively dim stars are very common in the universe, making up at least 80 percent of the total number of stars. Theoretical calculations suggested planets in the habitable zones close to red dwarfs are more likely to have weaker magnetic fields, especially in the case of so-called super-Earths, large rocky planets up to 10 times Earth’s mass. Astrobiologists were concerned these weak magnetic fields could make them poor candidates for life, but these new findings suggest weak magnetic fields are less of a problem than they thought.

Future research can examine how increasing radiation affects the evolution of life, Atri said. “Most studies of radiation’s effects on life mostly expose organisms to very high doses of radiation to see if they get killed or not, but I think systematic studies that gradually increase the radiation microbes receive could show how they evolve in environments that receive a lot of cosmic rays,” he said.