Back in the heyday of department stores, Olga Soffer stood at the center of the action.

As special events coordinator for Abraham & Straus, a shopping mecca on Fulton Street in Brooklyn, Ms. Soffer organized fashion shows, cooking festivals and other programs to reel in customers.

She loved her job, but after more than a decade it began to feel more tedious than chic.

“I stopped caring,” she later wrote, “if it was navy blue or dark brown socks that were the next hot item.”

So she went to graduate school, became an archaeologist and wound up embarking on a primitive second act in fashion, unearthing startling revelations about ice age clothing and the role that women played in prehistoric textile production.

“The transition from one career in fashion promotion to another in archaeology did take some time, but it was never boring,” she wrote in an autobiography she produced for family and friends.

Professor Soffer died on June 20 at her home in Los Angeles. She was 83. Her death, which was not widely reported, was confirmed by her daughter, Alex Beattie, who did not provide a cause.

Becoming one of the world’s top experts on the Upper Paleolithic period, Professor Soffer helped establish that the wardrobes of ice age people weren’t limited to animal hides, as had been previously thought.

Her research showed that they had produced woven cloth, string skirts and caps — among other necessities, including belts, nets and baskets — thousands of years earlier than scholars believed.

“She made the invisible visible,” Michael Petraglia, a professor of archaeology and human evolution at Griffith University in Australia, said in an interview. “She really changed the complexion of the field. This is a giant loss in archaeology and anthropology.”

Professor Soffer’s breakthrough discovery came in the 1990s, as she sifted through thousands of fired-clay fragments, dating back more than 26,000 years, that had been excavated from settlements in what is now Czechia.

Under magnification, she noticed faint parallel lines in the fragments. She photographed them, writing, “plant fibers?” in her notebook, the lines having tantalizingly suggested the production of textiles.

Several years later, James M. Adovasio, an expert on ancient fiber technologies at Mercyhurst University in Pennsylvania, visited her at home in Illinois. She projected slides of the fragments on her refrigerator door, and Professor Adovasio went “absolutely ballistic,” she told The New York Times in 1995.

Her hunch had been correct.

Standing in her kitchen, Professor Adovasio told her “that the lines were the impressions of textiles, making them by far the earliest such artifacts,” as he, Professor Soffer and Jake Page wrote in “The Invisible Sex: Uncovering the True Roles of Women in Prehistory” (2007).

There was also evidence of woven baskets and nets used in hunting.

Intrigued, Professor Soffer decided to reanalyze Venus figurines found in Europe, searching for evidence of clothing that might have been missed in previous studies (which had largely been conducted by men, she liked to note).

Sure enough, she and her collaborators found carved details depicting caps, skirts, belts and garments worn across the chest.

Because women were the primary crafters in subsequent societies, Professor Soffer concluded that they had probably played the same role in prehistoric times.

“Women were not just out there to reproduce,” she told Scientific American in 2000. “They were actively involved in production as well, just as women are in any and all societies that we know of.”

What’s more, the nets probably gave women the ability to help with hunting, especially for small animals like rabbits.

“Life was lived by more than stone spear point,” she told The Times in 2012. “It gets us away from the Hemingway, mega-macho male stuff.”

Olga Aleksandrovna Shabunin was born on Sept. 9, 1942, in Belgrade, the capital of Nazi-occupied Yugoslavia during World War II. Her father, Alexander Shabunin, was a Canadian immigrant who owned rental properties; her mother, Galina (Girs) Shabunin, was an administrative assistant.

The sound of explosions echoed throughout Olga’s childhood. The family’s house, she later wrote, “was some five blocks from the old Belgrade Main Railway Station — a location that was repeatedly bombed during the war, first by the Axis powers, then by the Allied ones.”

When she was an infant, her parents sent her to live with her maternal grandparents in Veliki Beckerek (now Zrenjanin), a rural city about 50 miles north of Belgrade. Soon after she arrived, the Nazis captured the city and sent them to a labor camp.

“My grandmother used to tell me that being incredibly blonde and Aryan looking, I was a big hit with the commander of the camp, whose daughter back home in Germany I ostensibly resembled,” she wrote. “He would, Grandma told me, often come to take me to the officers’ mess hall at dinner time for some decent food and warmth.”

Back in Belgrade, her father lost his Canadian citizenship and was jailed. He was released when the war ended.

In 1955, the family immigrated to the United States, settling in Brooklyn, where Olga’s father assembled window blinds and her mother worked as a seamstress.

After high school, Olga enrolled at Hunter College in Manhattan, majoring in political science. She graduated in 1965, and her first job was with Abraham & Straus.

“What followed,” she wrote, “were years in a fun and glamorous job where I discovered and promoted fashion trends and devised all possible ways of using fashion to lure customers into the store.”

Eventually, feeling restless, she enrolled in graduate school at Hunter, taking courses in art history at night. Gradually, she drifted toward paleoanthropology and ethnography, immersing herself in other times and cultures.

She received a master’s degree in anthropology in 1975 and then entered a doctoral program at the City University of New York. She wrote her dissertation on the prehistoric archaeology of Eastern Europe.

At first, the career change baffled her friends.

“It was like, ‘Wait, you’re doing what?’” Marcia Hurwitz, an Abraham & Straus colleague and lifelong friend who became a Hollywood agent, said in an interview. “But ultimately it made sense. She wanted more in life — we all did. She was always way more evolved than being in fashion.”

Professor Soffer taught at Hunter, Lehman College and the University of Wisconsin-Milwaukee before joining the University of Illinois in 1985.

Before turning to prehistoric fashion, she excavated sites in Russia and Ukraine — a difficult undertaking for someone from the United States, especially a woman.

“She had to work with older Soviet men who were really dominant in the field,” Professor Petraglia said. “It takes a really special, determined person to do that. She was pretty amazing.”

Her marriage to Mark Soffer, a high school history teacher, ended in divorce in 1979. She married Dmitry V. Bobyshev, a poet and translator, the same year; they divorced in 1991.

In addition to Ms. Beattie, her daughter from her first marriage, she is survived by two grandchildren.

Professor Soffer’s research was widely (and amusingly) covered in the media.

“Furs for Evening, But Cloth Was the Stone Age Standby,” a 1999 Times headline read.

Introducing a segment on Professor Soffer, the “Nightline” host Chris Bury said, “Tonight, the real caveman couture.”

Even she had some fun with it.

“That skirt is to die for,” Professor Soffer told The Times, describing a little number she discovered on a Venus figurine. “Though maybe it’s an acquired taste.’‘

Flying over the southwestern Amazon, archaeologists have discovered hundreds of ancient, monumental designs carved in the earth that hint at complex societies in the rainforest a millennium before Spanish and Portuguese colonists arrived.

The research, published this week in the journal Nature, shows circles, squares and other geometric figures, some with connecting roads, beneath the forest canopy, with nearly 400 previously unknown earthworks in all. Many are formations that archaeologists call geoglyphs and date from between 600 B.C. to 850 A.D. All of them add to evidence contradicting the depiction of the Amazon as a largely untouched expanse before the arrival of Europeans in the 15th century.

To see under the dense canopy near the borders of Bolivia, Brazil and Peru, the researchers used a laser-scanning technology called lidar — an acronym for light detection and ranging — which archaeologists and other scholars around the world have used to map sites invisible to the naked eye.

The geoglyphs, shaped by embankments, mounds and trenches, vary in size. Most span seven acres, including many with ditches 30 feet wide and 15 feet deep. The biggest figure sprawls across more than 120 acres.

“This is an important and ambitious study, based on exceptionally extensive lidar coverage for this region, which reveals the remarkable scale of pre-Columbian landscape modification in southwestern Amazonia,” said José Iriarte, an archaeologist at the University of Exeter who was not involved in the research.

Further excavation, he said, would be crucial in investigating the geoglyphs, which in many ways remain mysterious, including “how they were used and whether they were associated with residence, ceremonies or other activities.”

Drawing in part on oral accounts from the Apurinã nation, the Indigenous group that lives in the center of the earthwork area, the researchers said that the designs likely had several purposes.

“We are quite sure that those are used for festivities, political occasions, ceremonies, dance, music and also competition like ball games,” said Martti Pärssinen, the lead author and an emeritus professor at the University of Helsinki.

The researchers attributed the structures to an ancient society they called the Aquiry, which Dr. Pärssinen described as a multicultural, multilingual group that “shared a common cosmology” reflected in these ceremonial centers.

“Nobody has totally figured out” the exact purpose or meaning of the geoglyphs, which may have astronomically related forms, said Anna Roosevelt, a professor of anthropology at the University of Illinois Chicago, who was not on the team.

Dr. Pärssinen said the archaeologists had not found any evidence of permanent residence at the mounds from the Aquiry era, which ended around 900 A.D. Nor did they believe any were meant to be defensive structures.

But the structures, stretching across a zone of 1,700 square miles, build on evidence that the Amazon basin was widely and densely populated in the centuries before Columbus. Chroniclers like Gaspar de Carvajal, a missionary who traveled the Amazon in the 1540s with the conquistador Francisco de Orellana, described a land “thickly populated” in some places, with many large settlements, including one that “stretched for five leagues without there intervening any space from house to house.”

Those accounts were largely dismissed in the centuries that followed, given the crushing toll that disease and colonization took on Indigenous people. Scientists who followed also struggled to see how large or complex societies could develop without European-style agriculture, contributing to a false idea that the Amazon was a pristine forest, rather than one where the population was almost wiped out.

“Archaeologists find all of these things that are not supposed to be found in Amazonia, and it’s not because Amazonia is different in terms of the soil but how you use the forest,” Dr. Roosevelt said.

Recent work in other parts of the Amazon has found the traces of roads, canals, plazas and residential platforms, including in eastern Ecuador. Dr. Pärssinen’s team estimated that there may be thousands more earthworks in the region, and noted that the rainforest remains so dense in some places that even lasers could not pierce the foliage.

In other places, scientists warned, deforestation for agriculture may have damaged or destroyed sites. “This heritage is highly threatened by logging and soybean farming,” said Eduardo Neves, an archaeologist at the University of São Paulo, who was not on the team.

Dr. Pärssinen’s team also suggested that at the peak of Aquiry society, between 100-300 A.D., the total population of just this region may have reached up to three million people.

Population estimates are a subject of intense and sometimes thorny debate among researchers. Some experts said that the latest study’s proposal should be treated with caution, since it extrapolates not from excavated settlements but from a number of other factors, like how many earthwork sites may be in the region and how many people were probably needed to build and maintain them.

But most scientists now hold that the 16th-century accounts of dense populations were not as far-fetched as many generations believed.

“They thought that it was imagination of Carvajal and the expedition of Orellana, which saw really huge settlements,” Dr. Pärssinen said.