An extensive new analysis further confirms the oldest known human footprints in North America date back to the last ice age (about 23,500–21,700 years). To pinpoint their origins, researchers at the University of Arizona relied on cutting-edge methods at the United States Geological Survey (USGS) Radiocarbon Laboratory to examine hundreds of thousands of prehistoric pollen grains extracted from the tracks. According to researchers writing this week in the journal Science Advances, the team can even describe some of the dramatic environmental fluctuations experienced by these prehistoric humans within a single generation.

New Mexico’s White Sands National Park contains more than stunning vistas and desert dunes. It’s also home to one of the most controversial (and consequential) prehistoric discoveries of the last century. In 2006, archaeologists located footprints inside a dry lakebed that they later determined to be the earliest evidence of humans in North America. But there was a problem. Until then, researchers largely agreed that the first humans migrated into the continent about 16,000–12,000 years ago via Beringia, the subcontinent once connecting Alaska to Russia.

However, the White Sands footprints were estimated to be around 23,000 years old. That implied a sustained human presence on the continent at least seven millennia earlier than expected. Various archeological camps continued debating the true age of the White Sands footprints for years, while others cited similar—and sometimes older— sites in both North and South America. Meanwhile, the dry lakebed’s rarely seen geological conditions allowed researchers like University of Arizona geoscientist Jessica Tierney to learn more than each footprint’s age.

“The White Sands sediments are unique in that they allow us to reconstruct environmental conditions during the last ice age at a very high temporal resolution, so that we can see fluctuations that were relevant for the humans present at that time,” Tierney said.

Combining geochemical sediment signatures with the fossilized pollen, researchers accurately determined ancient regional details such as plant distribution, precipitation, temperature, and aridity. They soon learned that the humans who made the White Sands footprints would have experienced incredibly dramatic environmental shifts within their own lifetimes. Within only a few decades, the surrounding conifer forests transformed into plains covered with oak and sage. Lake Oterio, a giant body of water that once covered New Mexico’s national park, fluctuated in size for about 1,500 years until it receded completely. Although these shifts were large, they actually closely followed similar global climate changes at the time.

“And throughout that whole sequence, people were walking there, leaving their tracks alongside those of mammoths, giant sloths and dire wolves,” added Tierney.

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Marine biologists are sounding the alarm on behalf of the Galápagos Islands’ marine iguana (Amblyrhynchus cristatus). Without tightened regulations on the often abused exotic pet trade, researchers warn that a recent “strange uptick” in illegal animal trafficking combined with this season’s Super El Niño is further endangering the already vulnerable reptiles living on the Eastern Pacific archipelago.

“They are already shrinking in size and facing mass mortality, either by starvation or by trying to swim longer distances in search of food,” Juan José Alava, a marine ecotoxicologist at Canada’s Simon Fraser University, explained in a recent letter published in Science.

The marine iguana family encompasses at least 11 known subspecies, each specially evolved to live on the Galápagos Islands. They are the only reptiles in the world capable of foraging underwater for macroalgae, which makes up the majority of their diet. Although iguana colonies remain relatively stable, the International Union for Conservation of Nature (IUCN) still lists them as Vulnerable due to predators, mounting pollution issues, and cyclical El Niño events. Ten of the 11 recognized subspecies are also locally classified as either Critically Endangered or Endangered. Sale of iguanas is banned under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), but a recent uptick in illegal trafficking along with increasingly dramatic climate shifts is adding more stress to the situation.

Ecuadorian authorities have caught people attempting to smuggle iguanas multiple times this year. In May, officials discovered at least a dozen animals inside handbags at an airport that were bound for illegal markets. Law enforcement found another 32 tied up inside a suitcase intended for similar buyers in August. Many trafficked iguanas won’t survive the stress and rough handling, but even rescued reptiles face challenges. Because subspecies are evolved to live on specific islands, ecologists must test each rescued iguana’s DNA to determine where to return them.

Smuggling hasn’t been seen within the Galápagos Marine Reserve itself, but Alava and his colleagues theorize that smugglers are capturing iguanas near Ecuador’s coastal shorelines. Traffickers then obtain CITES permits that falsely declare the reptiles are captive bred in other nations, even though no such authorized facilities actually exist. Often, smugglers are only engaged in the industry out of financial necessity or coercion.

“Artisinal fishing communities from Galapagos and coastal Ecuador, who are facing severe socioeconomic hardship and expanding organized crime activities, may feel pressured to participate in this international black market,” the letter’s authors wrote.

Conservationists are now urging a multifaceted approach to protect the animals. CITES representatives need to close existing permit loopholes, while the Ecuadorian government should focus on simultaneously breaking up organized crime and providing economic aid to struggling communities.

“Maintaining global ocean observing systems is essential, and extreme marine event forecasting and response capabilities are improving,” the authors wrote. “But responsibility and action remain fragmented across environmental [organizations], fisheries, and emergency management, and public health agencies.”

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Even after decades of meteorological advances, weather forecasting remains infamously difficult. Today’s most trusted models are rarely accurate beyond a two-week window due to a constant cascade of atmospheric and climatic variables. These unpredictable meteorological interactions are the foundations of chaos theory. The interdisciplinary field studies how even the world’s most predictable systems can still produce completely unpredictable results, and was first developed by MIT mathematician Edward Lorenz during the 1970s.

“He came up with this theoretical two-week limit where beyond that, we just can’t predict weather because the noise in the system grows so much that it overwhelms any signal you start with,” Judah Cohen, a climatologist also at MIT, explained.

According to Cohen, many climate researchers continue to view Lorenz’s two-week hurdle as insurmountable. And that assumption has largely proven true for nearly 50 years. Even today’s dynamical simulations and artificial intelligence models begin to break down when attempting to predict conditions two-to-six weeks in the future—a window known as subseasonal forecasting. Nicknamed the “predictability desert,” this range runs into slow-moving, highly variable forces like this year’s super El Niño event. Once those factors enter the equation, forecasting becomes more of a roll of the dice l than anything concrete. However, Cohen has had his suspicions about chaos theory’s limitations.

“I never really believed that completely,” he said. “In theory, the atmosphere can create an infinite number of patterns, but it likes to fall into these favorite patterns over and over again.”

To try and break this forecasting barrier, Cohen and his colleague Lester Mackey have spent years developing an AI system that not only minimizes forecasting errors, but learns from its inevitable mistakes through a method called postprocessing. With postprocessing, the AI improves by comparing the inaccuracies with existing historical data, and then adjusts from there.

Cohen’s team recently submitted three versions of their model featuring the postprocessing system the European Center for Medium-Range Weather Forecasts (ECMWF). Widely known as the world’s best forecasting hub, the ECMWF also hosts seasonal competitions that pit the latest prediction models against one another. Most of these systems have relied on historic climate averages to reach their conclusions, but this was the first time a group submitted a program with postprocessing capabilities.

Cohen and his colleagues reported their results in a study published today in the journal Nature. Their AI postprocessing integration blew the existing forecasting models out of the water. For the two-to-six-week subseasonal window, researchers doubled overall prediction accuracy. Such massive improvements could soon help the farmers and energy providers who already rely on subseasonal forecasts, but the benefits may even save lives.

“It also improves predictions of extreme weather events, whether it’s flooding or cold spells or something else,” said Cohen. “It’s really important to predict both, but extreme events might be the most impactful part of this for society.” 

Many researchers have long presumed subseasonal forecasting to be a dead end, but the latest leap may clear the way to even bigger advances in the field.

“People have questioned if it’s even worth investing in models at all for this time range,” said Cohen. “[But] we consistently beat climatology averages with our models.”

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Thanks to some medieval human teeth, archaeologists have pinpointed when lead production first expanded across Europe during the Middle Ages. By examining dental enamel collected from graves located in central England, researchers now know the post-Roman society started mining and smelting again during the mid-7th century. As the team explains in a study published today in the journal Antiquity, the consequences of exposure to the toxic were stark—but distributed unequally among locals.

Humanity’s complicated relationship with lead dates back over 9,000 years, and our environmental exposure to the toxic metal is traceable as far as two million years ago. Lead was instrumental in prehistoric smelting advancements, and its invaluable properties paved technological progress all the way through the Industrial Revolution. However, lead is now known to cause various early developmental issues and its uses are dwindling, but tracing our reliance on the material helps contextualize and understand a society’s historical arc.

Researching these metals also isn’t easy. From the 16th to 19th centuries, manufacturers constantly re-smelted lead waste from ancient Rome and medieval England, which destroyed any discernible way to examine its prior origins and uses. Archaeologists including University of Nottingham’s Christopher Loveluck knew of another way to trace lead production in the Derbyshire Peak District, one of Europe’s largest providers of the metal during the Middle Ages

“The team is delighted to have finally confirmed definitively the date by which the early medieval lead industry was established in the Peak District…through evidence provided by the people themselves,” Loveluck said in the study’s accompanying announcement.

Archaeologists analyzed teeth from bodies buried in three Peak District cemeteries dating back to between 650 and 1500 CE. More specifically, they focused on tooth enamel. The external protective layer finishes forming during childhood, meaning any prior lead exposure stays embedded in the enamel for the rest of an individual’s life. Loveluck and his colleagues discovered that by the 7th century, the Derbyshire children’s lead levels were the same, if not higher, than those of children who lived in industrialized cities during the mid-18th and 19th centuries. By the mid-8th century, the growing lead industry had even begun to seep into surrounding regions like Castleton.

Teeth samples showed lead exposure reached its highest levels during the late 12th and early 13th centuries, which aligns with previous historical and environmental data. While the metal’s presence was ubiquitous among the population, it wasn’t necessarily the same across class or gender. High status gravesites included weapons and other personal items with lower lead concentrations than those seen in the graves of poorer residents. This implies that while the upper class owned lead-imbued possessions, they were higher quality objects. Meanwhile, working class families employed in mines and factories routinely exposed their children to larger amounts of lead.

There is also evidence that suggests women were especially at risk during this era. Three women who died between 17 and 25 years old showed particularly increased lead quantities in their tooth enamel. Overall, most of the men survived to middle or old age, while women often died during young adulthood.

“Our results indicate that in these mining communities, girls and boys alike were raised in dangerously polluted home environments,” said Castleton excavation co-director and study co-author Anna Bloxam. “This exposure…perhaps contributed to higher rates of premature death among women of child-bearing age.”

Lead contamination is still a serious issue today, although overall conditions have improved greatly since medieval England. Still, the underlying problems of environmental degradation and socio-economic vulnerabilities remain relevant today.

“This study has enabled us, for the first time…to look more deeply into the profound impact lead production had on individuals and the communities they lived in,” added University of Sheffield historian and study co-author Colin Merrony.

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