Humankind’s bombs, plastics, chickens and more have altered the planet enough to usher in a new chapter in Earth’s geologic history. That’s the majority opinion of a group of 35 experts tasked with evaluating whether the current human-dominated time span, unofficially dubbed the Anthropocene, deserves a formal place in Earth’s geologic timeline alongside the Eocene and the Pliocene.

In a controversial move, the Anthropocene Working Group has declared that the Anthropocene warrants being a full-blown epoch (not a lesser age), with its start pegged to the post–World War II economic boom and nuclear weapons tests of the late 1940s and early 1950s. The group made these provisional recommendations August 29 at the International Geological Congress in Cape Town, South Africa.
If eventually approved by the International Commission on Stratigraphy (ICS) — the gatekeepers of geologic time — and the Executive Committee of the International Union of Geological Sciences, the Anthropocene would usurp the current Holocene Epoch, which has reigned since the end of the last glacial period around 11,700 years ago. The Holocene would become the shortest completed epoch in history, just thousandths the length of the next shortest epoch.

“We’ve left an indelible mark on the Earth,” says Jan Zalasiewicz, a geologist at the University of Leicester in England and convener of the working group. “We now cannot go back to anything that’s ostensibly the same as the Holocene.”

Not all scientists are onboard with the plan. Critics say it’s grounded in politics and pop culture, not science, and that not enough time has passed to put just decades-old changes in context. Any proposal advocating for the Anthropocene will face strong skepticism, says Whitney Autin, a sedimentary geologist at the State University of New York at Brockport. “The idea of amending geologic time carries the same weight as eliminating an amendment to the U.S. Constitution,” he says.
To build its case for the new epoch, the working group will spend the next two to three years scouring natural records, such as rocks, mud and tree rings, for evidence that humankind’s impacts have brought about a distinct new phase in the stratigraphic record. The group will then submit a formal proposal for approval.

“We’re leaving physical signals in sediments, in corals, in trees that are going to be long lasting if not permanent,” says Colin Waters, a geologist at the British Geological Survey in Keyworth and a member of the working group. “It’s not just history, it’s geology as well.” And those geologic changes merit official recognition as a new epoch, Waters says.

The goal of the geologic time scale is to label and formalize discrete phases in Earth’s stratigraphic record as a tool for geologists and other scientists. This time scale allows scientists to easily identify, describe and discuss rocks of similar age across the planet.

The term “Anthropocene” has risen in popularity among scientists and the general public in recent years, driven in part by its use in a 2002 article by atmospheric chemist and Nobel laureate Paul Crutzen. The article argued that humans’ exploitation of natural resources has reshaped the planet enough to bring about a new epoch.

While “Anthropocene” now appears in the titles of papers, conference talks and books about everything from climate change to philosophy, those who embrace the term nonetheless disagree on its definition. Some researchers pin the start of the epoch to when humans first started converting forests to farmland thousands of years ago, while others, such as Crutzen, use the start of the Industrial Revolution or the recent acceleration in fossil fuel burning.

The Anthropocene Working Group was convened by the ICS in 2009 to sort out the definition of the Anthropocene and assess whether the time interval should be formally added to the geologic time scale. Among its 35 members, the working group contains an international mix of geologists, climate scientists, archaeologists and other experts.

In January, members of the working group published a review of evidence for the Anthropocene in Science. Pro-Anthropocene arguments come from multiple areas of science, from biology to climate to chemistry, the researchers reported. For instance, humans have introduced species such as the domestic chicken worldwide and driven many others to extinction (SN Online: 8/26/15). Emissions from human activities such as fossil fuel burning have altered Earth’s climate (SN: 4/16/16, p. 22). Manufactured materials such as plastics, aluminum and concrete will remain embedded in the ground as “technofossils.” Fallout from nuclear weapons tests has left a radioactive mark in soil, marine sediments and even ice. These human impacts make the Anthropocene distinct in the stratigraphic record from the Holocene, the researchers concluded.

For the Anthropocene to become official, the working group will have to establish a starting point for the proposed epoch. That can be accomplished by picking a nice round number — the Hadean-Archean switchover is an even 4 billion years ago, for instance — or by linking the starting point to a physical marker in the global sedimentary record, an approach now favored by ICS.

The marker for the start of the Holocene, for instance, is linked to chemical and physical changes in the Greenland ice sheet caused by the warming that brought Earth out of its last bout of glacial growth. Such markers — also called “golden spikes,” similar to the ceremonial spike that marked the union of the first U.S. transcontinental railroad — are chosen for being ubiquitous and consistent throughout the world.
Golden spikes are not necessarily important or even relevant to the differences that distinguish geologic time frames, says Stan Finney, a geologist at California State University, Long Beach, and former chair of the ICS. For instance, the Thanetian Age — a 3.2-million-year stretch during the Paleocene Epoch — is marked by just one of many reversals in Earth’s magnetic field.

While a golden spike’s geologic signal may be global, the official physical spike itself is literally a single point in the stratigraphic record somewhere on Earth. (A single point avoids the problem of using multiple points that could end up having different ages, muddling the time boundary.) The golden spike for the Holocene is inside an ice core collected from Greenland and kept chilled in a freezer at the University of Copenhagen.

The need for a golden spike shaped the working group’s Anthropocene proposal, Zalasiewicz says. While phases in human history such as early agriculture and the Industrial Revolution have had profound impacts on the planet, they didn’t have a simultaneous worldwide effect that could be used to mark the start of the new epoch. Had a major volcanic eruption spewed a distinctive layer of ash across the globe near the start of the Industrial Revolution, “it would have been a pretty good candidate,” Zalasiewicz says. Even though the eruption would have had nothing to do with human activity, the ash would have been a ubiquitous and easily identifiable marker for geologists.

Radioactive carbon and plutonium blasted from the ramp up in atmospheric nuclear tests during the 1950s is another story. And the timing is so recent that it opens up many new places to hunt for the proposed epoch’s golden spike, including in living organisms such as trees and corals. “We’re a bit like confused kids wandering around an enormous sweetshop wondering how we’re going to choose,” Zalasiewicz says.

Even if the group finds a golden spike, its proposal will face criticism from scientists who contend that the Anthropocene doesn’t warrant its own epoch. Radioactive fallout “is a widespread marker that qualifies for the rules that they need to follow to make a recommendation,” says William Ruddiman, a professor emeritus at the University of Virginia in Charlottesville, “but that doesn’t mean that it’s right, or that it makes sense.”

Not enough time has passed since the proposed start date of the Anthropocene to have enough perspective to put the observed changes in the sedimentary record in proper context, Autin says. “A lot of stratigraphers would say that maybe in thousands or millions of years there will be a distinctive demarcation in the rock record at this point in time, but right now it’s a proposal that’s premature.”

Placing the boundary so recently is “dubious, to say the least,” agrees Mike Walker, a professor emeritus at the University of Wales Trinity Saint David who helped establish the golden spike that represents the start of the Holocene. Divisions of geologic time “should have a utility for geoscientists, archaeologists, anthropologists, et cetera,” he says. “I see little of value to the wider science community in an epoch boundary at A.D. 1950.”

The formalization of the Anthropocene is not just scientifically motivated, but also driven by a desire to highlight humankind’s impact on the environment, suggests Lucy Edwards, a geologist with the U.S. Geological Survey in Reston, Va. “It’s a meme,” she says. “The thinking is that if you have a concept and you give it a new word, it carries more weight.”

The motivation behind the newly announced proposal isn’t overly focused on humankind being to blame for recent changes, Zalasiewicz responds. “If we had all the same changes, but caused by something else, like volcanoes or a meteorite or my cat, then it would be just as significant.”

More time isn’t needed to recognize that modern sediments are unique, he adds. After all, he says, if humans had been around 50 years after the environmental catastrophe that wiped out the dinosaurs about 66 million years ago, they would have clearly seen that Earth’s environment and ecology had permanently changed.

ORLANDO, Fla. — When sex chromosomes among common pill bugs go bad from disuse, borrowed bacterial DNA comes to the rescue. Certain pill bugs grow up female because of sex chromosomes cobbled together with genes that jumped from the bacteria.

Genetic analysis traces this female-maker DNA to Wolbachia bacteria, Richard Cordaux, based at the University of Poitiers with France’s scientific research center CNRS, announced September 29 at the International Congress of Entomology.

Various kinds of Wolbachia infect many arthropods, spreading from mother to offspring and often biasing their hosts’ sex ratios toward females (and thus creating even more female offspring). In the common pill bug (Armadillidium vulgare), Wolbachia can favor female development in two ways. Just by bacterial infection without any gene transfer, bacteria passed down to eggs can make genetic males develop into functional females. Generations of Wolbachia infections determining sex let these pill bugs’ now-obsolete female-making genes degenerate. Which makes it very strange that certain populations of pill bugs with no current Wolbachia infection still produce abundant females. That’s where Cordaux and Poitier colleague Clément Gilbert have demonstrated a second way that Wolbachia makes lady pill bugs — by donating DNA directly to the pill bug genes.
The researchers, who share an interest in sex determination, have built a case that Wolbachia inserted feminizing genes into pill bug chromosomes. The bacterial genes thus created a new sex chromosome.

“Incredible,” said Steve Perlman after hearing the talk, not in disbelief but in wonder at the biology. Perlman, of the University of Victoria in Canada, studies symbiosis and parasitism and says this new example of far-flung gene transfer is part of “a big thing in the field now.” Such transfers provide exotic genetic variation that fuels evolutionary processes. Audience members Ellen Martinson and Vincent Martinson, both of the University of Rochester in New York, were themselves coauthors of a 2016 paper describing microsporidian fungus DNA that has become a venom gene in some wasps.

The world’s most minuscule machines operate on the molecular level and have won their creators the 2016 Nobel Prize in chemistry. The prize is shared between Jean-Pierre Sauvage of the University of Strasbourg in France, J. Fraser Stoddart of Northwestern University in Evanston, Ill., and Bernard Feringa of the University of Groningen in the Netherlands.

Sauvage and colleagues first linked two ring-shaped molecules together in 1983 to form a necklacelike chain. In 1991, Stoddart’s team created an atom-scale axle, paving the way to build molecular “muscles” and “elevators.” Through electrochemistry, Feringa and colleagues powered up the first light-powered molecular motor in 1999 and even designed a four-wheel drive, nano-sized car.

These fantastic machines have opened up the molecular world to manipulating and moving objects at the smallest levels imaginable. There are “endless opportunities,” Feringa said in a phone interview during the announcement ceremony.

Scaling up from one cell to many may have been a small step rather than a giant leap for early life on Earth. A single-celled organism closely related to animals controls its life cycle using a molecular toolkit much like the one animals use to give their cells different roles, scientists report October 13 in Developmental Cell.

“Animals are regarded as this very special branch, as in, there had to be so many innovations to be an animal,” says David Booth, a biologist at the University of California, Berkeley who wasn’t part of the study. But this research shows “a lot of the machinery was there millions of years before animals evolved.”
Multicellular organisms need to be able to send messages between their cells and direct them to particular roles within the body. That requires a great deal of cell-to-cell coordination — something that unicellular organisms don’t have to deal with. But an amoeba (Capsaspora owczarzaki) employs many of those same tricks to switch its single-celled body between different life stages. That means that the earliest animals were probably “recycling mechanisms that were already present before,” says study coauthor Iñaki Ruiz-Trillo, a biologist at the Institute for Evolutionary Biology in Barcelona.

C. owczarzaki goes through three different life stages, acting independently in some stages and aggregating with other amoebas in others. Ruiz-Trillo and colleagues analyzed C. owczarzaki’s proteome — its complete set of proteins — during each life stage.

The amoeba made different amounts of its proteins in each life stage, the team found, suggesting that it was responding to new demands. But it went a step further, too, also shifting the way its proteins behaved during each stage.

Proteins can change their behavior by grabbing on to a molecular fragment called a phosphate ion. The phosphate ion’s effect depends on where it sticks to the protein and whether there are other phosphate ions stuck on nearby. C. owczarzaki showed distinct differences in the pattern of these phosphate add-ons between its three life stages. That parallels what’s seen in animals: Proteins in different organs within the same animal show similar modification differences.

The researchers also found changes in the molecules that control the protein modification process. Certain enzymes within a cell act like molecular concierges, helping phosphate ions latch on to proteins. The type of enzyme often determines where the ion sticks — and thus the effect it has. For instance, enzymes called tyrosine kinases often guide modifications that help multicellular organisms send messages between cells. Those enzymes aren’t thought to be widely used by single-celled species, says study coauthor Eduard Sabidó, a biologist at the Centre for Genomic Regulation in Barcelona. But C. owczarzaki uses these enzymes across all of its life stages, generating them in different quantities depending on the stage.
Previous research showed that other single-celled organisms had the genes for tyrosine signaling, but this study shows how widely it’s actually used and how closely it’s linked to specific life changes, says Booth.

The shared molecular mechanisms suggest that the unicellular common ancestor of today’s animals and C. owczarzaki probably used these same tricks, too, paving the way for multicellular life. That’s not to say animals don’t get any credit, says Sabidó — they’ve expanded this toolkit further over time. But the perceived chasm between a simple single-celled existence and a complex multicellular one might not have required a flying leap to cross. “This gap,” Sabidó says, “maybe isn’t such a gap.”

To the bafflement of birders, yellow-shafted flickers (Colaptes auratus auratus) sometimes sport red or orange wing feathers.

Scientists have suggested that the birds, which inhabit eastern North America, might be products of genetic variation affecting the carotenoid pigments that produce their flight-feather colors. Alternatively, the birds might be hybrids from mixing with a subspecies that lives in the west, red-shafted flickers (Colaptes auratus cafer). Despite decades of study, no clear-cut explanation has emerged.

It turns out that diet may be to blame. Jocelyn Hudon of the Royal Alberta Museum in Canada and her colleagues tested the red flight feathers from two yellow-shafted flickers and found traces of rhodoxanthin, a deep red pigment found in plants, and a potential metabolite. This suggests that the birds’ bodies break down rhodoxanthin — a clue that the pigment enters the body through food. Spectral and biochemical tests of feathers from museum collections also point to rhodoxanthin and suggest that the pigment may mess with yellow carotenoid production as well.

Yellow-shafted flickers probably pick up the red pigment when they eat berries from invasive honeysuckle plants, which contain the ruby pigment and produce similar red hues in other birds, the researchers write October 12 in The Auk. The plants also happen to produce berries just around the time that flickers molt their flight feathers.

PASADENA, Calif. — The forecast on Pluto is clear with less than a 1 percent chance of clouds. Images from the New Horizons spacecraft show hints of what could be a few isolated clouds scattered around the dwarf planet, the first seen in otherwise clear skies.

Seven cloud candidates appear to hug the ground in images taken shortly after the probe buzzed by the planet in July 2015. Along the line where day turns to night, several isolated bright patches appear. These are consistent with clouds forming at sunset and sunrise, said mission head Alan Stern during an October 18 news conference at a meeting of the American Astronomical Society’s Division for Planetary Sciences.

If they are clouds, they’re probably made of ethane, acetylene or hydrogen cyanide, based on what researchers have learned about Pluto’s atmosphere — though they might not be clouds, just reflective splotches on the surface, Stern said. Without stereo imaging, it’s impossible to tell how high off the ground the patches are, or whether they’re in the sky at all. Since New Horizons isn’t returning to Pluto — it’s hurtling deep into the Kuiper belt — the spacecraft won’t be able to take another look at the cloud candidates and answer these questions. That will have to wait until another spacecraft goes back to orbit Pluto, Stern said.

The Schiaparelli Mars lander, missing in action since its October 19 descent, dinged the surface of the Red Planet. A black spot framed by dark rays of debris mark the lander’s final resting place, the European Space Agency reports online October 27. Its parachute, still attached to the rear heat shield, lies about 1.4 kilometers to the south, new images from the Mars Reconnaissance Orbiter show. The front heat shield, ejected about four minutes into the descent, sits roughly 1.4 kilometers to the east of the impact site.

Radio contact with Schiaparelli was lost about 50 seconds before its planned landing. Early analysis of data from the lander indicate that the parachute was jettisoned prematurely and that the landing rockets shut off just a few seconds after igniting. Engineers with ESA’s ExoMars mission are still analyzing that data to understand what went wrong.

Below most volcanoes, Earth packs some serious deep heat. Mount St. Helens is a standout exception, suggests a new study. Cold rock lurks under this active Washington volcano.

Using data from a seismic survey (that included setting off 23 explosions around the volcano), Steven Hansen, a geophysicist at the University of New Mexico, peeked 40 kilometers under Mount St. Helens. That’s where the Juan de Fuca tectonic plate releases fluids due to intense heat and pressure as it descends beneath the North American plate. Those fluids rise and trigger melting in the rock above, fueling an arc of volcanoes that line up like lights on a runway. All except for Mount St. Helens, which stands apart about 50 kilometers to the west. Still, Hansen and colleagues expected to see a heat source under Mount St. Helens, as seen at other volcanoes.
Instead, thermal modeling revealed a wedge of a rock called serpentinite that’s too cool to be a volcano’s source of heat, the researchers report November 1 in Nature Communications. “This hasn’t really been seen below any active arc volcanoes before,” Hansen says.

This odd discovery helps show what the local crust-mantle boundary looks like, but raises another burning question: Where is Mount St. Helens’ heat source? Somewhere to the east, suggests Hansen. Exactly where, or how it reaches the volcano, remains a cold case.

Editor’s Note: this article was revised on January 4, 2017, to note how the Juan de Fuca tectonic plate fuels the chain of volcanoes.

It’s a familiar sight: Your mom or grandmother picks up a document and immediately holds it out at arm’s length to make out the small letters on the page, while simultaneously reaching for her reading glasses. As people age, their ability to see things close up often fades, a condition known as presbyopia. The eye can no longer focus light on the retina, focusing it instead just behind and causing poor close-up vision.

Many have thought that presbyopia was a consequence of living in an era in which people are overburdened by tasks that require frequently focusing in the near-field of vision. But perhaps not: A new study finds that if bonobos could read, they too would need glasses as they age.

Bonobos aren’t burdened with having to read tiny newsprint or letters on a mobile phone screen, but they do perform one task that regularly requires close focus: grooming. This behavior not only removes tiny bits of dirt and ectoparasites from the animals but also promotes social relationships. Most of the time, a bonobo grooms by putting its face within 20 centimeters of its partner and picking off the offending debris with its fingers. But older bonobos place their partner at arm’s length, probably because they can no longer see close up, researchers report November 7 in Current Biology.

For more than 40 years, researchers from Japan’s Kyoto University have studied wild bonobos in the Luo Scientific Reserve near a village called Wamba. Some researchers had noticed that older bonobos groomed differently than young ones, keeping their companions at arm’s length. Then in 2015, Heunglin Ryu of Kyoto University and colleagues decided to try to quantify this. Was it all older bonobos, or just some? They photographed 14 bonobos as they groomed, using the bonobos’ ear length and a ruler to determine grooming distance. Then they plotted out their data.

Grooming distance increased exponentially after a bonobo hit age 35, with the oldest bonobos, at age 45, keeping their partners around five times as far away as did young bonobos. A video of one bonobo taken in 2009 showed how her vision changed. When Ki was 29 years old, she placed his face 11.9 centimeters from her fingers as she plucked away at her partner. But at age 35, that had increased to 16.9 centimeters.

Scientists had reported anecdotes of older female chimpanzees (male chimps generally do not reach old age) that developed presbyopia. The bonobo finding combined with our own bad eyesight may indicate that presbyopia is a condition that dates to at least our most recent common ancestor.

As in humans, bad eyesight may come with a price for older bonobos. People who are farsighted often have trouble seeing in the dark. If that is also true for bonobos, they may have difficulty seeing in the low light of the rainforest canopy. Plus, if they are not able to groom others well, that may affect their social lives. Maybe they would benefit from reading glasses.

Global emissions of carbon dioxide won’t increase much in 2016 despite overall economic growth, newly released bookkeeping suggests. The result marks a three-year-long plateau in the amount of CO2 released by human activities, scientists from the Global Carbon Project report November 14 in Earth System Science Data.

The group’s projected rise in CO2 emissions of 0.2 percent for 2016 is far lower than the rapid emissions growth of around 2.3 percent annually on average from 2004 through 2013. Emissions increased by about 0.7 percent in 2014 over the previous year and remained largely flat in 2015.

China is largely responsible for the emissions slowdown, the researchers write. The country is the world’s largest carbon dioxide emitter and is projected to reduce its CO2 emissions by 0.5 percent this year.