A teenage girl climbed into an underground cave around 13,000 years ago. Edging through the ink-dark chamber, she accidentally plunged to her death at the bottom of a deep pit.

Rising seas eventually inundated the cave, located on Central America’s Yucatán Peninsula. But that didn’t stop scuba divers from finding and retrieving much of the girl’s skeleton in 2007.

“First Face of America,” a new NOVA documentary airing February 7 on PBS, provides a closeup look at two dangerous underwater expeditions that resulted in the discovery and salvaging of bones from one of the earliest known New World residents, dubbed Naia.
The program describes how studies of Naia’s bones (SN: 6/14/14, p. 6) and of genes from an 11,500-year-old infant recently excavated in Alaska have generated fresh insights into how people populated the Americas. Viewers watch anthropologist and forensic consultant James Chatters, who directed scientific studies of Naia’s remains, as he reconstructs the ancient teen’s face and charts the lower-body injuries that testify to what must have been a rough life.
In one suspenseful scene, cameras record Chatters talking with scuba divers shortly before the divers descend into the submerged cave to collect Naia’s bones. The scientist describes how thousands of years of soaking in seawater have rendered the precious remains fragile. He uses a plaster cast of a human jaw to demonstrate for scuba diver Susan Bird how to handle Naia’s skull so that it stays intact while being placed in a padded box. Bird’s worried expression speaks volumes.

“On the day of the dive, there was so much tension, so many people on the verge of freaking out,” Bird recalls in the show. When the divers return from their successful mission, collective joy breaks out.
The scene then shifts to a lab where Chatters painstakingly re-creates what Naia looked like. Asian-looking facial features raise questions about how the ancient youth ended up in Central America. That’s where University of Alaska Fairbanks anthropologist Ben Potter enters the story. In 2013, Potter and colleagues excavated the remains of two infant girls at an Alaskan site dating nearly to Naia’s time. Analysis of DNA recovered from one of the infants , described in the Jan. 11 Nature , supports a scenario in which a single founding Native American population reached a land bridge that connected northeast Asia to North America around 35,000 years ago. As early as 20,000 years ago, those people had moved into their new continent, North America. Naia’s face reflects her ancestors’ Asian roots.
In tracing back how people ended up in the Americas, NOVA presents an outdated model of ancient humans moving out of Africa along a single path through the Middle East around 80,000 years ago. Evidence increasingly indicates that people started leaving Africa 100,000 years ago or more via multiple paths (SN: 12/24/16, p. 25). That’s a topic for another show, though. In this one, Naia reveals secrets about the peopling of the Americas with a lot of help from intrepid scuba divers and state-of-the-art analyses. It’s fitting that a slight smile creases her reconstructed face.

Bedbugs leave a lasting legacy.

Their poop contains a chemical called histamine, part of the suite of pheromones that the insects excrete to attract others of their kind. Human exposure to histamine can trigger allergy symptoms like itchiness and asthma. (Our bodies also naturally release histamine when confronted with an allergen.) Histamine stays behind long after the bedbugs disappear, scientists report February 12 in PLOS ONE.

Researchers from North Carolina State University in Raleigh collected dust from apartments in a building with a chronic bedbug infestation. After a pest control company treated the apartments by raising the temperature to a toasty 50° Celsius, the researchers sampled the dust again. They compared those two sample groups with a third, from area homes that hadn’t had bedbugs for at least three years.

Dust from the infested apartments had levels of histamine chemical that were 22 times as much as the low amount found in bedbug-free houses, the researchers found. And while the heat treatment got rid of the tiny bloodsuckers, it didn’t lower the histamine levels.

Future pest control treatments might need to account for bedbugs’ long-term effects.

AUSTIN, Texas — An analysis of the metals in dozens of Picasso’s bronze sculptures has traced the birthplace of a handful of the works of art to the outskirts of German-occupied Paris during World War II.

This is the first time that the raw materials of Picasso’s sculptures have been scrutinized in detail, conservation scientist Francesca Casadio of the Art Institute of Chicago said February 17 at the annual meeting of the American Association for the Advancement of Science. And the elemental “fingerprints” help solve a mystery surrounding the sculptures’ origins.
“In collaboration with curators, we can write a richer history of art that is enriched by scientific findings,” Casadio said.

Casadio and colleagues from the Art Institute of Chicago and Northwestern University in Evanston, Ill., studied 39 bronzes in the collection of the Picasso Museum in Paris. The team used a portable X-ray fluorescence spectrometer to record the amount of copper, tin, zinc and lead at several points on each sculpture.
Based on the percentage of tin versus zinc in the bronze, “we found that there are compositional groups that relate to a specific foundry,” Casadio said. Seventeen sculptures had a foundry mark on them, so the researchers could relate metal mixes to specific foundries.
But seven sculptures lack foundry marks. Based on their composition, researchers pegged five to a specific foundry — that of Émile Robecchi, a craftsman whose workshop sat in the southern outskirts of Paris. Original invoices from the foundry surfaced two years ago and revealed when some of the pieces were cast. For instance, the description, weight and size written on one invoice confirmed that the bronze of Tête de femme de profil (Marie­Thérèse) — a portrait of one of Picasso’s mistresses originally sculpted in plaster in 1931 — was cast at the foundry in February 1941.
At that time, the war had been under way for years and the Germans had just occupied Paris. Picasso worried that his fragile plaster sculptures could be easily destroyed and sought to have them cast in bronze.

The team’s analysis also found two distinct mixtures of bronze that came out of the Robbechi foundry. That difference makes sense in the context of 1940s occupied Paris, when the Germans instituted laws requiring that people turn in certain metals to go toward war efforts, Casadio said.

“A lot of [foundries’] archives are incomplete or nonexistent,” Casadio said. The new analysis “reinforces why it’s really important to collaborate and how science adds the missing piece of the puzzle.”

Chile’s Atacama Desert is so dry that some spots see rain only once a decade. Salt turns the sandy soil inhospitable, and ultraviolet radiation scorches the surface. So little can survive there that scientists have wondered whether snippets of DNA found in the soil are just part of the desiccated skeletons of long-dead microbes or traces of hunkered-down but still living colonies.

A rare deluge has solved that mystery. Storms that dumped a few centimeters of rain on the Atacama in March 2015 — a decade’s worth in one day — sparked a microbial superbloom, researchers report February 26 in Proceedings of the National Academy of Sciences.
That storm initially threw a wrench into plans for scientists to get a snapshot of microbial life under normal, hyperarid conditions in the Atacama. “But in the end, it came back as a lucky stroke,” says study coauthor Dirk Schulze-Makuch, an astrobiologist at the Technische Universität Berlin. He and his colleagues drove mining vehicles into the desert to collect soil samples just a few weeks after the storm, and then returned again in 2016 and 2017 to track changes as the moisture dissipated.

The team found microbes — a mix of extremophile archaea, bacteria and fungi — that were tolerant of desiccation, salinity and UV radiation. The kinds of species were fairly consistent across sampling sites, which suggests there’s something of a native microbial community that can survive in this salty sand by going dormant between periods of moisture, says Schulze-Makuch.

Schulze-Makuch and his colleagues also found evidence for enzymes that are by-products of cellular metabolism. And traces of ATP, the molecule that cells use for energy, lingered inside cells. Those markers of life were the most bountiful at the first sampling time, and then declined as the soil dried out again.

Collectively, it’s evidence that microbes aren’t just dying and leaving their DNA behind in the Atacama — they’re laying low to live another day. That’s encouraging to Schulze-Makuch: He’s interested in the Atacama as a proxy for conditions on Mars.
Armando Azua-Bustos, an astrobiologist at the Centro de Astrobiología in Madrid who was not part of this study, agrees. “If we’re finding that, on Earth, truly dry places are still inhabited,” he says. “That opens the door to finding life elsewhere in the universe.”