Matter: Neanderthals, the World’s First Misunderstood Artists

Neanderthals could use feathers and bird claws as ornaments, archaeologists found. But some scientists were skeptical about what these findings meant.

Neanderthals might have lived near modern humans, after all, and spotted them making things. Neanderthals were smart enough to copy the ornaments, the thinking went — but not enough to invent them.

This debate was fueled in part by technological uncertainty: It can be very difficult to pin down a firm date for human fossils and artifacts.

To determine the age of cave paintings, for example, researchers have traditionally relied on radiocarbon dating. But that method only works if the paint contains carbon-bearing ingredients, such as charcoal. Red ocher, by contrast, can’t be dated this way.

Making matters worse, radiocarbon dating becomes increasingly unreliable beyond about 40,000 years.

Dr. Zilhão joined with archaeologists Alistair G.W. Pike of the University of Southampton and Dirk L. Hoffmann, now at the Max Planck Institute for Evolutionary Anthropology in Germany, to see if the prehistory of European art could be brought into sharper focus.

Instead of studying radiocarbon, they would use a different clock to tell time.

As water seeps into caves, it may deposit milky crusts of minerals on the walls known as flowstones. Flowstones contain tiny amounts of uranium, which slowly breaks down into thorium. The older a flowstone gets, the more thorium builds up inside it.

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Archaeologists Dirk Hoffmann, left, and Alistair Pike sampling calcite crust atop a red ladder-like painting in the La Pasiega cave in Spain. Credit J. Zilhão

A flowstone covering a piece of cave art might give Dr. Zilhão and his colleagues a minimum age for its creation. The problem was that scientists usually needed big chunks to find enough uranium and thorium to measure. The flowstones on cave art were typically very small.

But Dr. Hoffman had been working on ways to drastically increase the sensitivity of the technology so that he could work with much smaller samples.

The researchers returned to caves in Spain where ancient paintings had been discovered over the past century. The artists had drawn abstract images on the cave walls, including long lines, patterns of dots, and the outline of a human hand.

The team found flowstones covering parts of the artworks and scraped away samples for dating. In three caves, it turned out, some of the art was over 64,000 years old — about 20,000 years earlier than the first evidence of modern humans in Europe.

“They must have been made by Neanderthals,” said Dr. Pike.

Wil Roebroeks, an archaeologist at Leiden University who was not involved in the new study, said the evidence was conclusive. “This constitutes a major breakthrough in the field of human evolution studies,” he said. “Neanderthal authorship of some cave art is a fact.”

Dating flowstones is a big advance on previous techniques for determining the age of cave art, but the technology has one major limitation: it can only assign a minimum age to cave paintings. Flowstones may have begun forming the day after a painting was finished — or 10,000 years afterward.

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Cueva de los Aviones, in eastern Spain, once was home to Neanderthals. Credit J. Zilhão

But a second study, which Dr. Zilhão and his colleagues published Thursday in the journal Science Advances, hints that Neanderthals might well have been painting long before 64,000 years ago.

The scientists traveled to a cave on the coast of Spain where Dr. Zilhão had earlier discovered shells that had been drilled with holes and painted with ocher.

In 2010, he and his colleagues had used radiocarbon dating to estimate the age of other shells in the same layer of rock at 45,000 to 50,000 years old.

That result did not tell the team who made the ornaments. Neanderthals might be responsible, but it was also possible that the earliest modern humans in Europe made them.

And the uncertainties of radiocarbon dating also had left open the possibility that the shells were, in fact, far older.

Dr. Zilhão returned to the cave in order to try uranium dating. He and his colleagues discovered a layer of flowstone sitting atop the rock where they had found the shell jewelry. That flowstone turned out to be about 115,000 years old.

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Side Effects: Sifrhippus, the First Horse, Got Even Tinier as the Planet Heated Up

Scientists have known that many mammals appear to have shrunk during the warming period, and the phenomenon fits well with what is known as Bergmann’s rule, which says, roughly, that mammals of a given genus or species are smaller in hotter climates.

Although the rule refers to differences in location, it seemed also to apply to changes over time. But fine enough detail was lacking until now.

In Science, Ross Secord, of the University of Nebraska-Lincoln; Jonathan Bloch, of the Florida Museum of Natural History at the University of Florida in Gainesville; and a team of other researchers report on the collection and analysis of Sifrhippus fossils from the Bighorn Basin.

They report that the little horse got 30 percent smaller over the first 130,000 years, and then — as always seems to happen with weight loss — shot back up and got 75 percent bigger over the next 45,000 years.

The fossils indicate that at its smallest Sifrhippus weighed about eight and a half pounds, and at its largest about 15 pounds.

Using fine-grained detail on both climate and body size, the researchers concluded that the change in size was, as suspected, driven primarily by the warming trend.

“It seems to be natural selection,” said Dr. Secord. He said animals evolved to be smaller during warming because smaller animals did better in that environment, perhaps because the smaller an animal is, the easier it is to shed excess heat.

Paul L. Koch, head of the department of earth and planetary sciences at the University of California, Santa Cruz, and a specialist in reconstructing ecosystems and climates from many millions of years ago, said, “The paper lets us see the effect of warming on mammals where the climate change is really large.”

Dr. Koch, who was not involved in the study, said he thought that the question of whether natural selection was the cause of the changes was still open, and that the disruption of ecosystems during the warming period might have led smaller animals to migrate to new locations.

The current warming period is occurring on a scale of hundreds of years, not thousands, and scientists can only speculate on whether modern mammals will shrink.

“It’s difficult to say that mammals are going to respond in the same way now,“ Dr. Secord said. “If I had to guess,” he said, he thinks some will get smaller. And, he said, some studies have shown some birds to be getting smaller in response to warming.

If warming continues at the highest rate projected, he said, there’s another question: “Can mammals keep up?” 

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