bizarre ancient species

 These bizarre ancient species are rewriting animal evolution 

Early fossils with guts, segmented bodies and other sophisticated features reveal a revolution in animal life — before the Cambrian explosion. 

Traci Watson Nature Magazine

The revolutionary animal lived and died in the muck. In its final hours, it inched across the sea floor, leaving a track like a tire print, and finally went still. Then geology set to work. Over the next half a billion years, sediment turned to stone, preserving the deathbed scene. The fossilized creature looks like a piece of frayed rope measuring just a few centimeters wide. But it was a trailblazer among living things. 

This was the earliest-known animal to show unequivocal evidence of two momentous innovations packaged together: the ability to roam the ocean floor, and a body built from segments. It was also among the oldest known to have clear front and back ends, and a left side that mirrored its right. Those same features are found today in animals from flies to flying foxes, from lobsters to lions. 

Paleontologist Shuhai Xiao marvels at the tracks left by this creature, Yilingia spiciformis, and how they captured evidence of its movement. In his cluttered office at Virginia Tech in Blacksburg, he shows off a slab of beige resin — a reproduction of the fossil, which was found in China’s Yangtze Gorges region and is now kept in a Chinese research institute. The replica captures a snapshot of a moment from 550 million years ago. Xiao, whose team formally described Yilingia last year1, traces the bumpy tracks it made immediately before its death. “It was just moving around, and it died suddenly,” he says. 

But that’s not the end of this creature’s story. Although nobody knows which category of life it belonged to — the group that includes earthworms is one possibility — Yilingia is helping to fill in key details about the evolution of animals. Most importantly, Yilingia shows that some quintessential animal traits had appeared half a billion years ago, earlier than previous definitive evidence, Xiao says. 

Yilingia is not the only creature from that region to provide some of the earliest fossil evidence for an important animal feature. In 2018, Xiao and his team reported2 on tracks found in the Yangtze Gorges consisting of two parallel rows of dimples. The researchers propose that the trails were made by an animal from 550 million years ago that might have been able to burrow and had multiple pairs of appendages — which would make it one of the earliest-known animals with legs. 

These Chinese fossils hail from a time right before the Cambrian explosion, the evolutionary transformation when most of the animal groups that populate the planet today first made their appearance in the fossil record. Scientists long regarded the boundary between the Cambrian period and the Precambrian as a dividing point in evolution — a transition from a world in which simple, strange organisms flourished, to a time when the seas teemed with complex creatures that are the forebears of nearly everything that followed. 

But a growing number of findings reveal that the time slice just before the Cambrian, known as the Ediacaran (635 million to 541 million years ago), was a pivot point of animal evolution — a period that includes the earliest fossil records of anatomical innovations, such as guts and legs, and the first appearance of complex behaviours such as burrowing. The insights into the Ediacarans’ powers lend support to a provocative idea: that the Cambrian explosion, that iconic evolutionary burst, was actually less revolutionary than many had thought. 

The Cambrian explosion “is just another phase of evolution”, says palaeobiologist Rachel Wood at the University of Edinburgh, UK. “It’s not a single flash event. It could not have happened without previous waves of innovation.” 

Tumultuous times 

The Ediacarans’ innovations came against a backdrop of planetary cataclysms. During this time, Earth was still recovering from a long, shivery chapter when ice covered much of the seas. A gigantic meteor slammed into what is now Australia and probably kicked up enough dust to trigger catastrophic changes around the globe. The planet’s very surface was splitting: during the Ediacaran, one supercontinent broke apart and another took shape as land masses smashed together. On the continents, no plants grew. In the ocean, oxygen levels swung wildly. 

Scientists once thought that complex life did not start until after all this tumult. In Charles Darwin’s day, no fossils had been found below the rock layers documenting the Cambrian explosion. That blank rock record troubled Darwin, who reasoned that if his theory of evolution were correct, there must have been life before the Cambrian’s riches. “The case at present must remain inexplicable,” he wrote in On the Origin of Species in 1859. 

What sparked the Cambrian explosion? 

‘Darwin’s dilemma’ would remain unsolved for a century. In the 1930s and 1940s, researchers found intriguing imprints in rocks in Australia and elsewhere, but those rocks were not definitively Precambrian. Then, several English schoolchildren finally gave the Ediacarans their big break in 1957. Scrambling through a local quarry, the students noticed a leaf-shaped imprint in the ancient stone. Geologist Trevor Ford at the University of Leicester, UK, went to see it — and recognized that it had been made by a living thing. Ford’s paper3 about the imprint provided definitive evidence that large, complex species lived in the Precambrian. He ventured that the type of organism was probably “an algal frond”. 

It almost certainly wasn’t. Ford’s proposal was among the first in a long list of mistaken ideas about the identity of Ediacaran organisms. As more were discovered, scientists tried valiantly to place them on the tree of life. Some of the fossils were towering structures that stood one metre tall; others resembled deflated air mattresses. They have been called lichens and algae, fungi and bacterial colonies. “Basically any interpretation you can name has been suggested,” says geobiologist Lidya Tarhan at Yale University in New Haven, Connecticut. 

Finally, an audacious theory broke through the welter of competing claims. In the 1980s and 1990s, palaeontologist Adolf Seilacher at the University of Tübingen in Germany proposed4,5 that many Ediacaran life forms were not animals, but instead belonged to a single, bizarre group that he called the Vendobionta. These organisms were “an evolutionary experiment that failed” when formidable predators arrived on the scene, Seilacher wrote. His ideas have fallen out of favour, but they challenged researchers to question their assumptions. “At the time it was brilliant thinking,” says geobiologist Simon Darroch at Vanderbilt University in Nashville, Tennessee. “Before that, everyone assumed they were all jellyfish, which was even more wrong.” 

Now, most scientists are reaching agreement that the Ediacarans were a grab bag of disparate life forms, rather than the self-contained group proposed by Seilacher. “It’s inappropriate to consider them a failed experiment,” says palaeontologist Frances Dunn at the University of Oxford, UK. “They represent the ancestors, probably, of lots of different things.” Many scientists — although not all — are also signing up to the idea that some fraction of the Ediacaran organisms were probably animals, including some that don’t look like any animal alive today. 

That idea dovetails with genetic evidence that animals, or metazoans, first appeared more than 600 million years ago, well before the Ediacaran. There are no definitive fossils to illustrate the dawn of the animals, but the early metazoans were probably small, soft, simple things, including ancestors of modern creatures such as sponges and corals. Eventually, animals developed left–right symmetry, which is packaged with a gut, mouth and anus. 

But it’s not easy to define which fossils are animals and which are not. “Would we know the first metazoan if we tripped over it?” Wood wonders. “Is our search image correct?” Those questions still dog scientists. 

Insight from imprints 

Although the Ediacaran fossils have bedevilled researchers for decades, new techniques are coaxing fresh insights out of previously intractable imprints. Take the baffling organisms in the genus Dickinsonia. Rounded and flat, they resembled segmented bath mats only a few millimetres thick, although they could reach nearly 1.5 metres in length. Their strange construction spawned theories that they were protists — a diverse group of mostly single-celled organisms that includes protozoa and some algae — or lichens, although many researchers suspected that they were animals. 

To try to settle the long-standing dispute, geobiologist Ilya Bobrovskiy, now at the California Institute of Technology in Pasadena, and his colleagues took a biochemical approach. Bobrovskiy used tweezers to harvest thin films of organic matter — the remnants of Dickinsonia specimens that lived more than 550 million years ago. Analysis of the fat molecules in these biofilms showed that they were breakdown products of cholesterol, which is found in animals’ cell membranes6. “Dickinsonia was indeed an animal,” Bobrovskiy says. 

Evidence indicates that Dickinsonia, an iconic organism of the Ediacaran period, was an animal.Credit: Zeytun Travel Images/Alamy 

Dickinsonia was a rather simple animal: it showed no evidence of a mouth or a gut. But earlier this year, scientists detailed what might be the oldest-known animal that had both. Called Ikaria wariootia, it lived at roughly the same time as the Dickinsonia specimens that Bobrovskiy’s team studied, or perhaps earlier7. 

This discovery resolves a long-standing Ediacaran whodunnit: what made the narrow, twisting burrows that cut through Ediacaran sediments? They are among the most common Ediacaran calling cards, but are so small — only 1.5–2 millimetres wide — that they must have been created by an elusively tiny organism. “We never thought we’d see it,” says palaeontologist Mary Droser at the University of California, Riverside. Then she got her hands on a 3D laser scanner. 

Droser and her colleagues used the scanner to image hundreds of tiny blobs found near the twisting burrows. The team’s high-resolution 3D reconstructions show that the blobs were, in fact, organisms7. They were smaller than grains of rice, but they had left–right symmetry and both a front and back end, and features of the burrows suggest that the creatures could control where they moved. Previous analysis showed that some burrows wend into and out of the buried bodies of larger organisms, implying that Ikaria was a scavenger — the earliest known. Droser’s team suggests that, to support Ikaria’s burrowing and scavenging habits, the tiny animal probably had a mouth, anus and gut. 

Ikaria wariootia was smaller than a grain of rice, but its trails suggest that the burrowing creature was capable of relatively sophisticated behaviours, such as feasting on other organisms.Credit: Sohail Wasif/UCR 

More evidence that Ediacarans had guts comes from tubular organisms called cloudinids that arose around 550 million years ago. Using high-resolution X-ray imaging to peer inside cloudinids’ outer tubes, researchers saw a long, cylindrical feature, which the authors say is the oldest gut in the fossil record8. The team found this feature in a cloudinid that most probably belonged to the genus Saarina, and it bolsters the case that some cloudinids were animals with left–right symmetry8, says palaeobiologist and study co-author Jim Schiffbauer at the University of Missouri, Columbia. The gut’s shape and other clues hint that Saarina could be an early annelid, an animal grouping that includes modern earthworms. 

Alien animals 

New approaches are producing evidence that even the most alien-looking Ediacarans might have been animals. Take the ‘frondose’ Ediacarans, which were built from collections of miniature branches reminiscent of a fern’s lacy foliage. Some frondose organisms resembled heads of lettuce, whereas the organism Charnia masoni looked like a palm branch stuck into the sea floor. Charnia and its close relatives had a ‘pseudo-fractal’ organization like that of no living creature: the fronds were made up of branches, which were made up of sub-branches, which were made up of still-smaller branches. 

Big data renews fight over animal origins 

Dunn and her colleagues borrowed tools from developmental biology to understand these oddities. The researchers noted that Charnia’s fronds invariably have the same outline: widest at the bottom, smallest at the tip, with no short branches in the middle. This uniformity, a product of how the organism grows, is not seen in plants or algae9. Despite the other-worldly appearance of Charnia and its kin, “they’re more closely related to animals than they are to anything else”, Dunn says. 

Researchers studying the Ediacaran have revealed other frondose quirks by turning to the tools of modern ecology. One such technique is spatial analysis, which involves ultra-precise mapping of a large set of organisms that are preserved precisely where they lived — information that is rarely available in palaeontology. But scientists have exactly such an array at their disposal in Newfoundland, Canada, which has thousands of frondose imprints. Among them are examples that date back 571 million years, making them the oldest-known organisms that are big enough to be seen without magnification. 

Some of Newfoundland’s most abundant residents from around this time belong to the genus Fractofusus, whose members looked like mounds of fronds in the shape of an overturned saucer. Like its cousin Charnia, Fractofusus might have been an animal with no modern analogue. Spatial analysis showed that many large Fractofusus specimens are surrounded by clusters of small ones10. “Children,” says palaeobiologist Charlotte Kenchington at the University of Cambridge, UK, who was a member of the team that published the findings10 in 2015. This pattern suggests that Fractofusus multiplied in part by shooting out long runners on which its young developed. 

Rocks in Newfoundland, Canada, preserve some of the oldest Ediacaran species, including ones that resembled the fronds of a fern.Credit: Alicejmichel (CC BY-SA 4.0) 

In a paper11 published earlier this year, scientists describe long, thin, fossilized threads, some stretching 4 metres, between frondose organisms in Newfoundland. These threads might have been reproductive runners, and could also have been used for nutrient transport or communication. Perhaps these organisms were “acting in each other’s best interests rather than just for themselves”, says palaeobiologist Alex Liu at the University of Cambridge, who co-wrote the paper11. 

Before the Big Bang 

As evidence mounts for Ediacaran innovation, a group of researchers is using these finds to question an icon of evolutionary history: the Cambrian explosion. In the past, researchers often spoke of this event as the Big Bang of evolution — a single, supreme episode that had no prelude and suddenly changed everything. But some researchers take the view that Ediacaran organisms were the founders of this revolution. The burst of new species in the Cambrian “didn’t just come out of thin air”, says Wood. “It must have been derived from something in the Ediacaran.” 

A common view holds that many Ediacaran organisms vanished at the Ediacaran–Cambrian boundary some 540 million years ago. But while excavating in a remote spot in Siberia, Wood and her team found Cambrian-type fossils, such as animals that lived in mineral-laden, tube-shaped shells, in Ediacaran-age rock12. 

How the earliest mammals thrived alongside dinosaurs 

Wood and her co-authors cited these fossils in a provocative 2019 paper13, which also noted that Ediacaran animals capable of burrowing into sediments survived into the Cambrian period. The ability to burrow is a hallmark of that time, when animals dug so enthusiastically that they tore up the sea floor, creating new ecological niches. But the Ediacarans took the first step, the authors say. The vaunted Cambrian explosion, “was simply one phase” in the rise of animal diversity, they contend. 

All of these findings tell a new story of animal evolution — but it is not yet clear whether the revision will stick. Some palaeontologists say that Wood’s argument, in trying to give the Ediacaran its due, gives short shrift to the Cambrian explosion — which marked the appearance of a vast number of creatures that fit clearly into modern animal groups. Xiao agrees that some Ediacaran animals survived into the Cambrian, but he argues that the big picture shows a mass die-off at the boundary between the two periods. And invertebrate palaeontologist Jean-Bernard Caron at the Royal Ontario Museum in Toronto, Canada, questions Wood’s tally of Ediacaran species that survived into the Cambrian. “We don’t really have the fossil record to support that,” he says. Wood responds that although the critique is fair, it’s clear that multiple Cambrian-style creatures first appeared in the Ediacaran. 

For all the contention, however, some researchers think that answers are just around the corner. Continued work on biomarkers could pin down whether various Ediacaran organisms were, in fact, animals. And palaeontologists are excavating new Ediacaran finds in places such as Iran and Russia, Darroch says. The latest approaches, such as spatial analysis, hold promise too, says Xiao. These could flesh out — at long last — what was going on in the oceans during the pivotal Ediacaran period. 

“I would just love to be swimming over these communities and see, finally, how are they really growing? What on Earth are they?” Wood says. “So much would become obvious.” 

China’s Stance on Homosexuality

 

China’s Stance on Homosexuality Has Changed. Its Textbooks Haven’t.

A lawsuit brought by a student is part of an effort to get schools, editors and publishers to recognize that being gay is not a mental disorder.

 

By Sui-Lee Wee

Early in college, Ou Jiayong had already learned two things. One, textbooks can be wrong. And two, it can be hard to change them — especially on topics as sensitive in China as homosexuality.

In 2016, during her first year at South China Agricultural University in her hometown, Guangzhou, she stumbled across a psychology textbook that described being gay as a mental disorder.

As a lesbian, Ms. Ou felt that was unacceptable, but the complaints she made went nowhere.

So Ms. Ou, who also uses the name Xixi, brought a lawsuit demanding that the publisher remove the reference and publicly apologize. Her case has renewed the conversation about tolerance and human rights in a country where discrimination based on sexual orientation is rampant and where homosexuality has long been seen as incompatible with the traditional emphasis on marriage.

In a letter to the judge, Ms. Ou, now 23, recalled being “deeply stung” when she read the textbook. “It brought back memories of being laughed at by my classmates because of my homosexuality,” she wrote in the letter, which her lawyer read aloud in court this summer, three years after the suit was filed.

The judge was unswayed. Last month, the court in Jiangsu Province in eastern China ruled in favor of the publisher, Jinan University Press, saying the content did not “contain factual errors.”

Ms. Ou’s case stunned many people who had no idea that some textbooks still classified homosexuality as a disease, said Peng Yanzi, director of L.G.B.T. Rights Advocacy China, an influential group that has led many awareness-raising campaigns. Citing a survey that a research group conducted in 2016 and 2017, out of the 91 psychology textbooks used in Chinese universities, almost half of them said that homosexuality was a type of disease. Several have been amended, Mr. Peng said, but “many more” remain.

A hashtag about Ms. Ou’s case on Weibo, a popular social media platform, generated 26.7 million views, and several Chinese newspapers covered the hearing in July. Three weeks after the verdict, a school in Jiangsu said it would amend a health education manual after an internet user highlighted a phrase in it that said: “Homosexuality goes against the laws of nature.”

Ms. Ou has also galvanized China’s L.G.B.T. communities, Mr. Peng said.

“Many admire her for doing this for three years, in particular gay people, who are encouraged by this kind of bravery,” he said.

In recent years, L.G.B.T. communities have been asserting their rights more forcefully, suing “gay conversion” clinics, employers and even the government. This year, as China prepared to adopt its first civil code, activists led an unsuccessful push for the legalization of same-sex marriage, flooding legislators with more than 230,000 online suggestions and letters.

Even though China decriminalized homosexuality in 1997 and removed it from an official list of psychiatric disorders in 2001, discrimination persists in employment, health care and other areas. Many people, including Ms. Ou, are not open with their families about being gay.

Darius Longarino, a research scholar in law at Yale Law School who has managed legal reform programs promoting L.G.B.T. rights in China, said Ms. Ou’s case had brought “a rights issue into a scientific and technical terrain where the evidence is all on your side.”

L.G.B.T. communities have tried that approach in the past. In 2015, a student sued the Ministry of Education over textbooks that describe homosexuality as an affliction, arguing that the government was responsible for ensuring the books’ quality and should disclose its approval process; she lost two years later. In 2014, a Chinese court ordered a clinic to compensate a man who underwent electroshock therapy designed to “cure” homosexuality, saying the clinic had committed consumer fraud.

But suing for discrimination is harder because Chinese law does not protect people based on their sexual identity. Like the case against the clinic, Ms. Ou’s lawsuit was couched as a violation of consumer rights, with her lawyers arguing that there were dozens of typos and other errors in the 2013 edition of “Mental Health Education for College Students,” a widely used textbook.

The most egregious error, they said, was this phrase: “Compared with the sexual orientation of most people, homosexuality can be seen as a mental disorder or a confusion of sexual desires.” Since homosexuality is no longer on China’s official list of psychiatric disorders, the phrase is factually incorrect and the publisher should be held liable, said Leon Ge, Ms. Ou’s lawyer.

As the case encountered repeated delays, Ms. Ou completed her degree in sociology in mainland China and moved to the semiautonomous territory of Hong Kong, where she now works for a labor rights organization.

“We used a very difficult method to sue, and after three years, we are still insisting that they correct the error,” Mr. Ge said. “That, in itself, is symbolic.”

Ms. Ou’s activism began in college, when she took courses on gender equality and joined an L.G.B.T. student group at another school.

She described the humiliation she felt her freshman year when she participated in a debate about whether a gay couple could form a family. One classmate cited a psychology textbook to argue against same-sex marriage. Another asked Ms. Ou how she would feel if she were surrounded by gay people.

“I’m gay,” Ms. Ou said, as the classroom erupted in laughter. She recalled that a male classmate responded, “Whatever you say about your own life is meaningless, the textbook is right!”

In May 2016, after Ms. Ou discovered the offending phrase in the textbook, she sent an email to the publisher but received no reply. She turned up at the publisher’s office with a letter signed by 300 people asking for the textbook to be revised. An employee accepted her letter, but no one followed up. She then contacted the provincial Press and Publication Bureau, which responded by saying that the content had no “factual or logical mistakes.”

 

She took the publisher to court the next year, driven by her classmates’ derogatory comments as well as the suicide of a gay student at a Guangzhou university in 2015.

When the hearing was finally scheduled for this summer, Ms. Ou could not return to the mainland in time because of pandemic restrictions. So she stayed up through the night writing two letters to the judge, including one that she asked to be read out in court.

In it, Ms. Ou argued that the judge and the publisher must have had their own experiences being ridiculed over personal qualities beyond their control.

“I believe you can empathize with the daily injustices that minority students face on campus: being isolated, cursed, beaten and even sexually assaulted,” she wrote. “We should not tolerate discrimination. We have to change.”

Ms. Ou said she was appealing the judge’s ruling against her, comparing the fight to her hobby of hiking.

“How can you just quit? You can only continue walking,” she said. “This is a path with no return.”

Liu Yi contributed research.

 

Particles Can Break the Speed of Light

 Quantum Tunnels Show How Particles Can Break the Speed of Light

Recent experiments show that particles should be able to go faster than light when they quantum mechanically “tunnel” through walls.

 

The bizarre rules of quantum mechanics allow a particle to occasionally pass through a seemingly impenetrable barrier.

Natalie Wolchover Quanta Magazine

No sooner had the radical equations of quantum mechanics been discovered than physicists identified one of the strangest phenomena the theory allows.

“Quantum tunneling” shows how profoundly particles such as electrons differ from bigger things. Throw a ball at the wall and it bounces backward; let it roll to the bottom of a valley and it stays there. But a particle will occasionally hop through the wall. It has a chance of “slipping through the mountain and escaping from the valley,” as two physicists wrote in Nature in 1928, in one of the earliest descriptions of tunneling.

Physicists quickly saw that particles’ ability to tunnel through barriers solved many mysteries. It explained various chemical bonds and radioactive decays and how hydrogen nuclei in the sun are able to overcome their mutual repulsion and fuse, producing sunlight.

But physicists became curious — mildly at first, then morbidly so. How long, they wondered, does it take for a particle to tunnel through a barrier?

The trouble was that the answer didn’t make sense.

The first tentative calculation of tunneling time appeared in print in 1932. Even earlier stabs might have been made in private, but “when you get an answer you can’t make sense of, you don’t publish it,” noted Aephraim Steinberg, a physicist at the University of Toronto.

It wasn’t until 1962 that a semiconductor engineer at Texas Instruments named Thomas Hartman wrote a paper that explicitly embraced the shocking implications of the math.

Hartman found that a barrier seemed to act as a shortcut. When a particle tunnels, the trip takes less time than if the barrier weren’t there. Even more astonishing, he calculated that thickening a barrier hardly increases the time it takes for a particle to tunnel across it. This means that with a sufficiently thick barrier, particles could hop from one side to the other faster than light traveling the same distance through empty space.

In short, quantum tunneling seemed to allow faster-than-light travel, a supposed physical impossibility.

“After the Hartman effect, that’s when people started to worry,” said Steinberg.

The discussion spiraled for decades, in part because the tunneling-time question seemed to scratch at some of the most enigmatic aspects of quantum mechanics. “It’s part of the general problem of what is time, and how do we measure time in quantum mechanics, and what is its meaning,” said Eli Pollak, a theoretical physicist at the Weizmann Institute of Science in Israel. Physicists eventually derived at least 10 alternative mathematical expressions for tunneling time, each reflecting a different perspective on the tunneling process. None settled the issue.

But the tunneling-time question is making a comeback, fueled by a series of virtuoso experiments that have precisely measured tunneling time in the lab.

 

In the most highly praised measurement yet, reported in Nature in July, Steinberg’s group in Toronto used what’s called the Larmor clock method to gauge how long rubidium atoms took to tunnel through a repulsive laser field.

“The Larmor clock is the best and most intuitive way to measure tunneling time, and the experiment was the first to very nicely measure it,” said Igor Litvinyuk, a physicist at Griffith University in Australia who reported a different measurement of tunneling time in Nature last year.

Luiz Manzoni, a theoretical physicist at Concordia College in Minnesota, also finds the Larmor clock measurement convincing. “What they measure is really the tunneling time,” he said.

The recent experiments are bringing new attention to an unresolved issue. In the six decades since Hartman’s paper, no matter how carefully physicists have redefined tunneling time or how precisely they’ve measured it in the lab, they’ve found that quantum tunneling invariably exhibits the Hartman effect. Tunneling seems to be incurably, robustly superluminal.

“How is it possible for [a tunneling particle] to travel faster than light?” Litvinyuk said. “It was purely theoretical until the measurements were made.”

What Time?

Tunneling time is hard to pin down because reality itself is.

At the macroscopic scale, how long an object takes to go from A to B is simply the distance divided by the object’s speed. But quantum theory teaches us that precise knowledge of both distance and speed is forbidden.

In quantum theory, a particle has a range of possible locations and speeds. From among these options, definite properties somehow crystallize at the moment of measurement. How this happens is one of the deepest questions.

The upshot is that until a particle strikes a detector, it’s everywhere and nowhere in particular. This makes it really hard to say how long the particle previously spent somewhere, such as inside a barrier. “You cannot say what time it spends there,” Litvinyuk said, “because it can be simultaneously two places at the same time.”

To understand the problem in the context of tunneling, picture a bell curve representing the possible locations of a particle. This bell curve, called a wave packet, is centered at position A. Now picture the wave packet traveling, tsunami-like, toward a barrier. The equations of quantum mechanics describe how the wave packet splits in two upon hitting the obstacle. Most of it reflects, heading back toward A. But a smaller peak of probability slips through the barrier and keeps going toward B. Thus the particle has a chance of registering in a detector there.

But when a particle arrives at B, what can be said about its journey, or its time in the barrier? Before it suddenly showed up, the particle was a two-part probability wave — both reflected and transmitted. It both entered the barrier and didn’t. The meaning of “tunneling time” becomes unclear.

And yet any particle that starts at A and ends at B undeniably interacts with the barrier in between, and this interaction “is something in time,” as Pollak put it. The question is, what time is that?

Steinberg, who has had “a seeming obsession” with the tunneling-time question since he was a graduate student in the 1990s, explained that the trouble stems from the peculiar nature of time. Objects have certain characteristics, like mass or location. But they don’t have an intrinsic “time” that we can measure directly. “I can ask you, ‘What is the position of the baseball?’ but it makes no sense to ask, ‘What is the time of the baseball?’” Steinberg said. “The time is not a property any particle possesses.” Instead, we track other changes in the world, such as ticks of clocks (which are ultimately changes in position), and call these increments of time.

But in the tunneling scenario, there’s no clock inside the particle itself. So what changes should be tracked? Physicists have found no end of possible proxies for tunneling time.

Tunneling Times

Hartman (and LeRoy Archibald MacColl before him in 1932) took the simplest approach to gauging how long tunneling takes. Hartman calculated the difference in the most likely arrival time of a particle traveling from A to B in free space versus a particle that has to cross a barrier. He did this by considering how the barrier shifts the position of the peak of the transmitted wave packet.

But this approach has a problem, aside from its weird suggestion that barriers speed particles up. You can’t simply compare the initial and final peaks of a particle’s wave packet. Clocking the difference between a particle’s most likely departure time (when the peak of the bell curve is located at A) and its most likely arrival time (when the peak reaches B) doesn’t tell you any individual particle’s time of flight, because a particle detected at B didn’t necessarily start at A. It was anywhere and everywhere in the initial probability distribution, including its front tail, which was much closer to the barrier. This gave it a chance to reach B quickly.

It’s part of the general problem of what is time, and how do we measure time in quantum mechanics, and what is its meaning.”

Eli Pollak

Since particles’ exact trajectories are unknowable, researchers sought a more probabilistic approach. They considered the fact that after a wave packet hits a barrier, at each instant there’s some probability that the particle is inside the barrier (and some probability that it’s not). Physicists then sum up the probabilities at every instant to derive the average tunneling time.

As for how to measure the probabilities, various thought experiments were conceived starting in the late 1960s in which “clocks” could be attached to the particles themselves. If each particle’s clock only ticks while it’s in the barrier, and you read the clocks of many transmitted particles, they’ll show a range of different times. But the average gives the tunneling time.

All of this was easier said than done, of course. “They were just coming up with crazy ideas of how to measure this time and thought it would never happen,” said Ramón Ramos, the lead author of the recent Nature paper. “Now the science has advanced, and we were happy to make this experiment real.”

Embedded Clocks

Although physicists have gauged tunneling times since the 1980s, the recent rise of ultraprecise measurements began in 2014 in Ursula Keller’s lab at the Swiss Federal Institute of Technology Zurich. Her team measured tunneling time using what’s called an attoclock. In Keller’s attoclock, electrons from helium atoms encounter a barrier, which rotates in place like the hands of a clock. Electrons tunnel most often when the barrier is in a certain orientation — call it noon on the attoclock. Then, when electrons emerge from the barrier, they get kicked in a direction that depends on the barrier’s alignment at that moment. To gauge the tunneling time, Keller’s team measured the angular difference between noon, when most tunneling events began, and the angle of most outgoing electrons. They measured a difference of 50 attoseconds, or billionths of a billionth of a second.

Then in work reported in 2019, Litvinyuk’s group improved on Keller’s attoclock experiment by switching from helium to simpler hydrogen atoms. They measured an even shorter time of at most two attoseconds, suggesting that tunneling happens almost instantaneously.

But some experts have since concluded that the duration the attoclock measures is not a good proxy for tunneling time. Manzoni, who published an analysis of the measurement last year, said the approach is flawed in a similar way to Hartman’s tunneling-time definition: Electrons that tunnel out of the barrier almost instantly can be said, in hindsight, to have had a head start.

Meanwhile, Steinberg, Ramos and their Toronto colleagues David Spierings and Isabelle Racicot pursued an experiment that has been more convincing.

This alternative approach utilizes the fact that many particles possess an intrinsic magnetic property called spin. Spin is like an arrow that is only ever measured pointing up or down. But before a measurement, it can point in any direction. As the Irish physicist Joseph Larmor discovered in 1897, the angle of the spin rotates, or “precesses,” when the particle is in a magnetic field. The Toronto team used this precession to act as the hands of a clock, called a Larmor clock.

The researchers used a laser beam as their barrier and turned on a magnetic field inside it. They then prepared rubidium atoms with spins aligned in a particular direction, and sent the atoms drifting toward the barrier. Next, they measured the spin of the atoms that came out the other side. Measuring any individual atom’s spin always returns an unilluminating answer of “up” or “down.” But do the measurement over and over again, and the collected measurements will reveal how much the angle of the spins precessed, on average, while the atoms were inside the barrier — and thus how long they typically spent there.

Samuel Velasco/Quanta Magazine

The researchers reported that the rubidium atoms spent, on average, 0.61 milliseconds inside the barrier, in line with Larmor clock times theoretically predicted in the 1980s. That’s less time than the atoms would have taken to travel through free space. Therefore, the calculations indicate that if you made the barrier really thick, Steinberg said, the speedup would let atoms tunnel from one side to the other faster than light.

A Mystery, Not a Paradox

In 1907, Albert Einstein realized that his brand-new theory of relativity must render faster-than-light communication impossible. Imagine two people, Alice and Bob, moving apart at high speed. Because of relativity, their clocks tell different times. One consequence is that if Alice sends a faster-than-light signal to Bob, who immediately sends a superluminal reply to Alice, Bob’s reply could reach Alice before she sent her initial message. “The achieved effect would precede the cause,” Einstein wrote.

Experts generally feel confident that tunneling doesn’t really break causality, but there’s no consensus on the precise reasons why not. “I don’t feel like we have a completely unified way of thinking about it,” Steinberg said. “There’s a mystery there, not a paradox.”

Tunneling “almost seems weirder than entanglement.”

Grace Field

Some good guesses are wrong. Manzoni, on hearing about the superluminal tunneling issue in the early 2000s, worked with a colleague to redo the calculations. They thought they would see tunneling drop to subluminal speeds if they accounted for relativistic effects (where time slows down for fast-moving particles). “To our surprise, it was possible to have superluminal tunneling there too,” Manzoni said. “In fact, the problem was even more drastic in relativistic quantum mechanics.”

Researchers stress that superluminal tunneling is not a problem as long as it doesn’t allow superluminal signaling. It’s similar in this way to the “spooky action at a distance” that so bothered Einstein. Spooky action refers to the ability of far-apart particles to be “entangled,” so that a measurement of one instantly determines the properties of both. This instant connection between distant particles doesn’t cause paradoxes because it can’t be used to signal from one to the other.

Considering the amount of hand-wringing over spooky action at a distance, though, surprisingly little fuss has been made about superluminal tunneling. “With tunneling, you’re not dealing with two systems that are separate, whose states are linked in this spooky way,” said Grace Field, who studies the tunneling-time issue at the University of Cambridge. “You’re dealing with a single system that’s traveling through space. In that way it almost seems weirder than entanglement.”

In a paper published in the New Journal of Physics in September, Pollak and two colleagues argued that superluminal tunneling doesn’t allow superluminal signaling for a statistical reason: Even though tunneling through an extremely thick barrier happens very fast, the chance of a tunneling event happening through such a barrier is extraordinarily low. A signaler would always prefer to send the signal through free space.

Why, though, couldn’t you blast tons of particles at the ultra-thick barrier in the hopes that one will make it through superluminally? Wouldn’t just one particle be enough to convey your message and break physics? Steinberg, who agrees with the statistical view of the situation, argues that a single tunneled particle can’t convey information. A signal requires detail and structure, and any attempt to send a detailed signal will always be faster sent through the air than through an unreliable barrier.

Pollak said these questions are the subject of future study. “I believe the experiments of Steinberg are going to be an impetus for more theory. Where that leads, I don’t know.”

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The pondering will occur alongside more experiments, including the next on Steinberg’s list. By localizing the magnetic field within different regions in the barrier, he and his team plan to probe “not only how long the particle spends in the barrier, but where within the barrier it spends that time,” he said. Theoretical calculations predict that the rubidium atoms spend most of their time near the barrier’s entrance and exit, but very little time in the middle. “It’s kind of surprising and not intuitive at all,” Ramos said.

By probing the average experience of many tunneling particles, the researchers are painting a more vivid picture of what goes on “inside the mountain” than the pioneers of quantum mechanics ever expected a century ago. In Steinberg’s view, the developments drive home the point that despite quantum mechanics’ strange reputation, “when you see where a particle ends up, that does give you more information about what it was doing before.”

 

 

AMERICAN PURPOSE

Liberalism and Its Discontents

The challenges from the left and the right.

Francis Fukuyama

Today, there is a broad consensus that democracy is under attack or in retreat in many parts of the world. It is being contested not just by authoritarian states like China and Russia, but by populists who have been elected in many democracies that seemed secure.

The “democracy” under attack today is a shorthand for liberal democracy, and what is really under greatest threat is the liberal component of this pair. The democracy part refers to the accountability of those who hold political power through mechanisms like free and fair multiparty elections under universal adult franchise. The liberal part, by contrast, refers primarily to a rule of law that constrains the power of government and requires that even the most powerful actors in the system operate under the same general rules as ordinary citizens. Liberal democracies, in other words, have a constitutional system of checks and balances that limits the power of elected leaders.

Democracy itself is being challenged by authoritarian states like Russia and China that manipulate or dispense with free and fair elections. But the more insidious threat arises from populists within existing liberal democracies who are using the legitimacy they gain through their electoral mandates to challenge or undermine liberal institutions. Leaders like Hungary’s Viktor Orbán, India’s Narendra Modi, and Donald Trump in the United States have tried to undermine judicial independence by packing courts with political supporters, have openly broken laws, or have sought to delegitimize the press by labeling mainstream media as “enemies of the people.” They have tried to dismantle professional bureaucracies and to turn them into partisan instruments. It is no accident that Orbán puts himself forward as a proponent of “illiberal democracy.”

The contemporary attack on liberalism goes much deeper than the ambitions of a handful of populist politicians, however. They would not be as successful as they have been were they not riding a wave of discontent with some of the underlying characteristics of liberal societies. To understand this, we need to look at the historical origins of liberalism, its evolution over the decades, and its limitations as a governing doctrine.

What Liberalism Was

Classical liberalism can best be understood as an institutional solution to the problem of governing over diversity. Or to put it in slightly different terms, it is a system for peacefully managing diversity in pluralistic societies. It arose in Europe in the late 17th and 18th centuries in response to the wars of religion that followed the Protestant Reformation, wars that lasted for 150 years and killed major portions of the populations of continental Europe.

While Europe’s religious wars were driven by economic and social factors, they derived their ferocity from the fact that the warring parties represented different Christian sects that wanted to impose their particular interpretation of religious doctrine on their populations. This was a period in which the adherents of forbidden sects were persecuted—heretics were regularly tortured, hanged, or burned at the stake—and their clergy hunted. The founders of modern liberalism like Thomas Hobbes and John Locke sought to lower the aspirations of politics, not to promote a good life as defined by religion, but rather to preserve life itself, since diverse populations could not agree on what the good life was. This was the distant origin of the phrase “life, liberty, and the pursuit of happiness” in the Declaration of Independence. The most fundamental principle enshrined in liberalism is one of tolerance: You do not have to agree with your fellow citizens about the most important things, but only that each individual should get to decide what those things are without interference from you or from the state. The limits of tolerance are reached only when the principle of tolerance itself is challenged, or when citizens resort to violence to get their way.

Understood in this fashion, liberalism was simply a pragmatic tool for resolving conflicts in diverse societies, one that sought to lower the temperature of politics by taking questions of final ends off the table and moving them into the sphere of private life. This remains one of its most important selling points today: If diverse societies like India or the United States move away from liberal principles and try to base national identity on race, ethnicity, or religion, they are inviting a return to potentially violent conflict. The United States suffered such conflict during its Civil War, and Modi’s India is inviting communal violence by shifting its national identity to one based on Hinduism.

There is however a deeper understanding of liberalism that developed in continental Europe that has been incorporated into modern liberal doctrine. In this view, liberalism is not simply a mechanism for pragmatically avoiding violent conflict, but also a means of protecting fundamental human dignity.

The ground of human dignity has shifted over time. In aristocratic societies, it was an attribute only of warriors who risked their lives in battle. Christianity universalized the concept of dignity based on the possibility of human moral choice: Human beings had a higher moral status than the rest of created nature but lower than that of God because they could choose between right and wrong. Unlike beauty or intelligence or strength, this characteristic was universally shared and made human beings equal in the sight of God. By the time of the Enlightenment, the capacity for choice or individual autonomy was given a secular form by thinkers like Rousseau (“perfectibility”) and Kant (a “good will”), and became the ground for the modern understanding of the fundamental right to dignity written into many 20th-century constitutions. Liberalism recognizes the equal dignity of every human being by granting them rights that protect individual autonomy: rights to speech, to assembly, to belief, and ultimately to participate in self-government.

Liberalism thus protects diversity by deliberately not specifying higher goals of human life. This disqualifies religiously defined communities as liberal. Liberalism also grants equal rights to all people considered full human beings, based on their capacity for individual choice. Liberalism thus tends toward a kind of universalism: Liberals care not just about their rights, but about the rights of others outside their particular communities. Thus the French Revolution carried the Rights of Man across Europe. From the beginning the major arguments among liberals were not over this principle, but rather over who qualified as rights-bearing individuals, with various groups—racial and ethnic minorities, women, foreigners, the propertyless, children, the insane, and criminals—excluded from this magic circle.

A final characteristic of historical liberalism was its association with the right to own property. Property rights and the enforcement of contracts through legal institutions became the foundation for economic growth in Britain, the Netherlands, Germany, the United States, and other states that were not necessarily democratic but protected property rights. For that reason liberalism strongly associated with economic growth and modernization. Rights were protected by an independent judiciary that could call on the power of the state for enforcement. Properly understood, rule of law referred both to the application of day-to-day rules that governed interactions between individuals and to the design of political institutions that formally allocated political power through constitutions. The class that was most committed to liberalism historically was the class of property owners, not just agrarian landlords but the myriads of middle-class business owners and entrepreneurs that Karl Marx would label the bourgeoisie.

Liberalism is connected to democracy, but is not the same thing as it. It is possible to have regimes that are liberal but not democratic: Germany in the 19th century and Singapore and Hong Kong in the late 20th century come to mind. It is also possible to have democracies that are not liberal, like the ones Viktor Orbán and Narendra Modi are trying to create that privilege some groups over others. Liberalism is allied to democracy through its protection of individual autonomy, which ultimately implies a right to political choice and to the franchise. But it is not the same as democracy. From the French Revolution on, there were radical proponents of democratic equality who were willing to abandon liberal rule of law altogether and vest power in a dictatorial state that would equalize outcomes. Under the banner of Marxism-Leninism, this became one of the great fault lines of the 20th century. Even in avowedly liberal states, like many in late 19th- and early 20th-century Europe and North America, there were powerful trade union movements and social democratic parties that were more interested in economic redistribution than in the strict protection of property rights.

Liberalism also saw the rise of another competitor besides communism: nationalism. Nationalists rejected liberalism’s universalism and sought to confer rights only on their favored group, defined by culture, language, or ethnicity. As the 19th century progressed, Europe reorganized itself from a dynastic to a national basis, with the unification of Italy and Germany and with growing nationalist agitation within the multiethnic Ottoman and Austro-Hungarian empires. In 1914 this exploded into the Great War, which killed millions of people and laid the kindling for a second global conflagration in 1939.

The defeat of Germany, Italy, and Japan in 1945 paved the way for a restoration of liberalism as the democratic world’s governing ideology. Europeans saw the folly of organizing politics around an exclusive and aggressive understanding of nation, and created the European Community and later the European Union to subordinate the old nation-states to a cooperative transnational structure. For its part, the United States played a powerful role in creating a new set of international institutions, including the United Nations (and affiliated Bretton Woods organizations like the World Bank and IMF), GATT and the World Trade Organization, and cooperative regional ventures like NATO and NAFTA.

The largest threat to this order came from the former Soviet Union and its allied communist parties in Eastern Europe and the developing world. But the former Soviet Union collapsed in 1991, as did the perceived legitimacy of Marxism-Leninism, and many former communist countries sought to incorporate themselves into existing international institutions like the EU and NATO. This post-Cold War world would collectively come to be known as the liberal international order.

But the period from 1950 to the 1970s was the heyday of liberal democracy in the developed world. Liberal rule of law abetted democracy by protecting ordinary people from abuse: The U.S. Supreme Court, for example, was critical in breaking down legal racial segregation through decisions like Brown v. Board of Education. And democracy protected the rule of law: When Richard Nixon engaged in illegal wiretapping and use of the CIA, it was a democratically elected Congress that helped drive him from power. Liberal rule of law laid the basis for the strong post-World War II economic growth that then enabled democratically elected legislatures to create redistributive welfare states. Inequality was tolerable in this period because most people could see their material conditions improving. In short, this period saw a largely happy coexistence of liberalism and democracy throughout the developed world.

Discontents

Liberalism has been a broadly successful ideology, and one that is responsible for much of the peace and prosperity of the modern world. But it also has a number of shortcomings, some of which were triggered by external circumstances, and others of which are intrinsic to the doctrine. The first lies in the realm of economics, the second in the realm of culture.

The economic shortcomings have to do with the tendency of economic liberalism to evolve into what has come to be called “neoliberalism.” Neoliberalism is today a pejorative term used to describe a form of economic thought, often associated with the University of Chicago or the Austrian school, and economists like Friedrich Hayek, Milton Friedman, George Stigler, and Gary Becker. They sharply denigrated the role of the state in the economy, and emphasized free markets as spurs to growth and efficient allocators of resources. Many of the analyses and policies recommended by this school were in fact helpful and overdue: Economies were overregulated, state-owned companies inefficient, and governments responsible for the simultaneous high inflation and low growth experienced during the 1970s.

But valid insights about the efficiency of markets evolved into something of a religion, in which state intervention was opposed not based on empirical observation but as a matter of principle. Deregulation produced lower airline ticket prices and shipping costs for trucks, but also laid the ground for the great financial crisis of 2008 when it was applied to the financial sector. Privatization was pushed even in cases of natural monopolies like municipal water or telecom systems, leading to travesties like the privatization of Mexico’s TelMex, where a public monopoly was transformed into a private one. Perhaps most important, the fundamental insight of trade theory, that free trade leads to higher wealth for all parties concerned, neglected the further insight that this was true only in the aggregate, and that many individuals would be hurt by trade liberalization. The period from the 1980s onward saw the negotiation of both global and regional free trade agreements that shifted jobs and investment away from rich democracies to developing countries, increasing within-country inequalities. In the meantime, many countries starved their public sectors of resources and attention, leading to deficiencies in a host of public services from education to health to security.

The result was the world that emerged by the 2010s in which aggregate incomes were higher than ever but inequality within countries had also grown enormously. Many countries around the world saw the emergence of a small class of oligarchs, multibillionaires who could convert their economic resources into political power through lobbyists and purchases of media properties. Globalization enabled them to move their money to safe jurisdictions easily, starving states of tax revenue and making regulation very difficult. Globalization also entailed liberalization of rules concerning migration. Foreign-born populations began to increase in many Western countries, abetted by crises like the Syrian civil war that sent more than a million refugees into Europe. All of this paved the way for the populist reaction that became clearly evident in 2016 with Britain’s Brexit vote and the election of Donald Trump in the United States.

The second discontent with liberalism as it evolved over the decades was rooted in its very premises. Liberalism deliberately lowered the horizon of politics: A liberal state will not tell you how to live your life, or what a good life entails; how you pursue happiness is up to you. This produces a vacuum at the core of liberal societies, one that often gets filled by consumerism or pop culture or other random activities that do not necessarily lead to human flourishing. This has been the critique of a group of (mostly) Catholic intellectuals including Patrick Deneen, Sohrab Ahmari, Adrian Vermeule, and others, who feel that liberalism offers “thin gruel” for anyone with deeper moral commitments.

This leads us to a deeper stratum of discontent. Liberal theory, both in its economic and political guises, is built around individuals and their rights, and the political system protects their ability to make these choices autonomously. Indeed, in neoclassical economic theory, social cooperation arises only as a result of rational individuals deciding that it is in their self-interest to work with other individuals. Among conservative intellectuals, Patrick Deneen has gone the furthest by arguing that this whole approach is deeply flawed precisely because it is based on this individualistic premise, and sanctifies individual autonomy above all other goods. Thus for him, the entire American project based as it was on Lockean individualistic principles was misfounded. Human beings for him are not primarily autonomous individuals, but deeply social beings who are defined by their obligations and ties to a range of social structures, from families to kin groups to nations.

This social understanding of human nature was a truism taken for granted by most thinkers prior to the Western Enlightenment. It is also one that is one supported by a great deal of recent research in the life sciences that shows that human beings are hard-wired to be social creatures: Many of our most salient faculties are ones that lead us to cooperate with one another in groups of various sizes and types. This cooperation does not arise necessarily from rational calculation; it is supported by emotional faculties like pride, guilt, shame, and anger that reinforce social bonds. The success of human beings over the millennia that has allowed our species to completely dominate its natural habitat has to do with this aptitude for following norms that induce social cooperation.

By contrast, the kind of individualism celebrated in liberal economic and political theory is a contingent development that emerged in Western societies over the centuries. Its history is long and complicated, but it originated in the inheritance rules set down by the Catholic Church in early medieval times which undermined the extended kinship networks that had characterized Germanic tribal societies. Individualism was further validated by its functionality in promoting market capitalism: Markets worked more efficiently if individuals were not constrained by obligations to kin and other social networks. But this kind of individualism has always been at odds with the social proclivities of human beings. It also does not come naturally to people in certain other non-Western societies like India or the Arab world, where kin, caste, or ethnic ties are still facts of life.

The implication of these observations for contemporary liberal societies is straightforward. Members of such societies want opportunities to bond with one another in a host of ways: as citizens of a nation, members of an ethnic or racial group, residents of a region, or adherents to a particular set of religious beliefs. Membership in such groups gives their lives meaning and texture in a way that mere citizenship in a liberal democracy does not.

Many of the critics of liberalism on the right feel that it has undervalued the nation and traditional national identity: Thus Viktor Orbán has asserted that Hungarian national identity is based on Hungarian ethnicity and on maintenance of traditional Hungarian values and cultural practices. New nationalists like Yoram Hazony celebrate nationhood and national culture as the rallying cry for community, and they bemoan liberalism’s dissolving effect on religious commitment, yearning for a thicker sense of community and shared values, underpinned by virtues in service of that community.

There are parallel discontents on the left. Juridical equality before the law does not mean that people will be treated equally in practice. Racism, sexism, and anti-gay bias all persist in liberal societies, and those injustices have become identities around which people could mobilize. The Western world has seen the emergence of a series of social movements since the 1960s, beginning with the civil rights movement in the United States, and movements promoting the rights of women, indigenous peoples, the disabled, the LGBT community, and the like. The more progress that has been made toward eradicating social injustices, the more intolerable the remaining injustices seem, and thus the moral imperative to mobilizing to correct them. The complaint of the left is different in substance but similar in structure to that of the right: Liberal society does not do enough to root out deep-seated racism, sexism, and other forms of discrimination, so politics must go beyond liberalism. And, as on the right, progressives want the deeper bonding and personal satisfaction of associating—in this case, with people who have suffered from similar indignities.

This instinct for bonding and the thinness of shared moral life in liberal societies has shifted global politics on both the right and the left toward a politics of identity and away from the liberal world order of the late 20th century. Liberal values like tolerance and individual freedom are prized most intensely when they are denied: People who live in brutal dictatorships want the simple freedom to speak, associate, and worship as they choose. But over time life in a liberal society comes to be taken for granted and its sense of shared community seems thin. Thus in the United States, arguments between right and left increasingly revolve around identity, and particularly racial identity issues, rather than around economic ideology and questions about the appropriate role of the state in the economy.

There is another significant issue that liberalism fails to grapple adequately with, which concerns the boundaries of citizenship and rights. The premises of liberal doctrine tend toward universalism: Liberals worry about human rights, and not just the rights of Englishmen, or white Americans, or some other restricted class of people. But rights are protected and enforced by states which have limited territorial jurisdiction, and the question of who qualifies as a citizen with voting rights becomes a highly contested one. Some advocates of migrant rights assert a universal human right to migrate, but this is a political nonstarter in virtually every contemporary liberal democracy. At the present moment, the issue of the boundaries of political communities is settled by some combination of historical precedent and political contestation, rather than being based on any clear liberal principle.

Conclusion

Vladimir Putin told the Financial Times that liberalism has become an “obsolete” doctrine. While it may be under attack from many quarters today, it is in fact more necessary than ever.

It is more necessary because it is fundamentally a means of governing over diversity, and the world is more diverse than it ever has been. Democracy disconnected from liberalism will not protect diversity, because majorities will use their power to repress minorities. Liberalism was born in the mid-17th century as a means of resolving religious conflicts, and it was reborn again after 1945 to solve conflicts between nationalisms. Any illiberal effort to build a social order around thick ties defined by race, ethnicity, or religion will exclude important members of the community, and down the road will lead to conflict. Russia itself retains liberal characteristics: Russian citizenship and nationality is not defined by either Russian ethnicity or the Orthodox religion; the Russian Federation’s millions of Muslim inhabitants enjoy equal juridical rights. In situations of de facto diversity, attempts to impose a single way of life on an entire population is a formula for dictatorship.

The only other way to organize a diverse society is through formal power-sharing arrangements among different identity groups that give only a nod toward shared nationality. This is the way that Lebanon, Iraq, Bosnia, and other countries in the Middle East and the Balkans are governed. This type of consociationalism leads to very poor governance and long-term instability, and works poorly in societies where identity groups are not geographically based. This is not a path down which any contemporary liberal democracy should want to tread.

That being said, the kinds of economic and social policies that liberal societies should pursue is today a wide-open question. The evolution of liberalism into neoliberalism after the 1980s greatly reduced the policy space available to centrist political leaders, and permitted the growth of huge inequalities that have been fueling populisms of the right and the left. Classical liberalism is perfectly compatible with a strong state that seeks social protections for populations left behind by globalization, even as it protects basic property rights and a market economy. Liberalism is necessarily connected to democracy, and liberal economic policies need to be tempered by considerations of democratic equality and the need for political stability.

I suspect that most religious conservatives critical of liberalism today in the United States and other developed countries do not fool themselves into thinking that they can turn the clock back to a period when their social views were mainstream. Their complaint is a different one: that contemporary liberals are ready to tolerate any set of views, from radical Islam to Satanism, other than those of religious conservatives, and that they find their own freedom constrained.

This complaint is a serious one: Many progressives on the left have shown themselves willing to abandon liberal values in pursuit of social justice objectives. There has been a sustained intellectual attack on liberal principles over the past three decades coming out of academic pursuits like gender studies, critical race theory, postcolonial studies, and queer theory, that deny the universalistic premises underlying modern liberalism. The challenge is not simply one of intolerance of other views or “cancel culture” in the academy or the arts. Rather, the challenge is to basic principles that all human beings were born equal in a fundamental sense, or that a liberal society should strive to be color-blind. These different theories tend to argue that the lived experiences of specific and ever-narrower identity groups are incommensurate, and that what divides them is more powerful than what unites them as citizens. For some in the tradition of Michel Foucault, foundational approaches to cognition coming out of liberal modernity like the scientific method or evidence-based research are simply constructs meant to bolster the hidden power of racial and economic elites.

The issue here is thus not whether progressive illiberalism exists, but rather how great a long-term danger it represents. In countries from India and Hungary to the United States, nationalist conservatives have actually taken power and have sought to use the power of the state to dismantle liberal institutions and impose their own views on society as a whole. That danger is a clear and present one.

Progressive anti-liberals, by contrast, have not succeeded in seizing the commanding heights of political power in any developed country. Religious conservatives are still free to worship in any way they see fit, and indeed are organized in the United States as a powerful political bloc that can sway elections. Progressives exercise power in different and more nuanced ways, primarily through their dominance of cultural institutions like the mainstream media, the arts, and large parts of academia. The power of the state has been enlisted behind their agenda on such matters as striking down via the courts conservative restrictions on abortion and gay marriage and in the shaping of public school curricula. An open question for the future is whether cultural dominance today will ultimately lead to political dominance in the future, and thus a more thoroughgoing rollback of liberal rights by progressives.

Liberalism’s present-day crisis is not new; since its invention in the 17th century, liberalism has been repeatedly challenged by thick communitarians on the right and progressive egalitarians on the left. Liberalism properly understood is perfectly compatible with communitarian impulses and has been the basis for the flourishing of deep and diverse forms of civil society. It is also compatible with the social justice aims of progressives: One of its greatest achievements was the creation of modern redistributive welfare states in the late 20th century. Liberalism’s problem is that it works slowly through deliberation and compromise, and never achieves its communal or social justice goals as completely as their advocates would like. But it is hard to see how the discarding of liberal values is going to lead to anything in the long term other than increasing social conflict and ultimately a return to violence as a means of resolving differences.

Francis Fukuyama, chairman of the editorial board of American Purpose, directs the Center on Democracy, Development and the Rule of Law at Stanford University.