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Portugal’s Oldest Skull Adds to Puzzle of Human Evolution

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Virtual reconstruction of the Aroeira 3 cranium as seen from the front (A), back (B), top (C), and side (D). Image Credit: Zilhão et al. in PNAS, 2017

 
When archaeologists were digging up the dirt floor at the Aroeira cave in central Portugal in 2014, they were already well on their way to understanding the lifestyle of hunter-gatherers who took shelter there during the Middle Pleistocene.

The researchers had found Acheulean handaxes—the most advanced technology of the day—that were used for cutting, scraping, and butchering. They also found burnt deer bones, suggesting that whoever camped out at this cave 400,000 years ago had the know-how to make fires—then a relatively new human achievement.

Then, at the end of the field season, the excavators unexpectedly struck paleoanthropological gold. They were using demolition hammers to break through the cave’s hard fragmented rock when they chipped a piece of bone.

“Immediately we knew we were dealing with a human fossil,” said University of Barcelona archaeologist João Zilhão, the director of the excavation. His team removed a block of the sediment surrounding the fossil, and preparators in Madrid spent two years carefully revealing a human cranium encased inside. Their findings are reported in the current issue of the Proceedings of the National Academy of Sciences.

It’s exceptionally rare to find human remains from this period. It’s even more rare to find them in a good archaeological context, among artifacts like tools and animal bones. So the discovery of this skull—the oldest ever found in Portugal—is exciting for some paleoanthropologists.

Below, you can see the researchers' discovery, removal, cleaning, and finally restoration of the ancient cranium.

Zilhão et al. in PNAS

 
The prehistoric skull from Aroeira shares some similarities with human fossils of the same era found in Spain, France, and Italy—including some fossils thought to be early Neanderthals, which were just starting to emerge in Europe, and some fossils that had been attributed to another species, Homo heidelbergensis. But the new specimen doesn’t fit neatly into a species category, and could help researchers argue for a diversity of human populations in Europe before the rise of modern humans.

Mental_floss spoke to a trio of experts in human evolution for their take on the current study, which they were not involved in. “This find adds more complexity to the European picture, as we are also seeing in Africa and Asia,” Chris Stringer, a paleoanthropologist at London’s Natural History Museum, says.

University College London paleoanthropologist Maria Martinón-Torres sees the skull as a potential ancestor to the Neanderthal. “I think this finding obliges us to abandon the idea that Neanderthal evolution is a single and lineal process,” she says.

She noted that there are several fossils from similar mid-Pleistocene sites, such as Sima de los Huesos in Atapuerca, Spain and Arago in France, that share some Neanderthal traits but have very different combinations of those traits.

“We see now that there is no linearity in the combination of these traits,” Martinón-Torres says. “This is probably due to the fragmentation and isolation of these populations due to the hard climatic conditions in Europe at that time.” She said that when climatic conditions are harsh, populations can get isolated and evolve their own particular distinctive features. Then, when conditions get better, these groups meet and recombine again. “So for a long period we will find a Neanderthal-like but highly variable population,” she says.

Bence Viola, a paleoanthropologist at the University of Toronto, notes that with the addition of the Aroeira skull we now have a few different humans fossils that look quite different from one another despite being from the same period. He says the new skull seems more primitive than the fossils found nearby at Sima de los Huesos, which, ancient DNA results have shown, represent early Neanderthals. “This cranium makes this scenario of having several different populations in Europe in the middle Pleistocene seem likely,” says Viola, who adds that he would be very interested to see what this specimen’s DNA looks like.

Stringer points out that the skull would be even more illuminating if it weren't missing some key parts, including the back of the cranium: “Unfortunately, this new fossil, interesting as it is, doesn’t have the most useful bits to put it into this puzzle."

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Dave Einsel, Stringer, Getty Images
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Stones, Bones, and Wrecks
9.7-Million-Year-Old Teeth Discovered in Germany Have Scientists Puzzled
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Dave Einsel, Stringer, Getty Images

Scientists in Germany say they've found ape teeth that are surprisingly similar to the teeth of an early human relative dating to millions of years later. As the Independent reports, the team of experts unearthed a pair of 9.7-million-year-old fossilized teeth that, they say, have some of the same features as the teeth of the hominid Australopithecus afarensis.

Scientists from the Natural History Museum in Mainz found the fossils a year ago in nearby Eppelsheim but have waited until now to publish their findings—partly because they weren't sure what to make of the puzzling discovery. Of the two teeth, a canine and a molar, the canine tooth bears a striking resemble to that from "Lucy," one of the first known ancient human relatives to walk upright, who lived in Africa some 3.2 million years ago.

"They are clearly ape teeth," researcher Herbert Lutz told local media in a press conference. "Their characteristics resemble African finds that are four to five million years younger than the fossils excavated in Eppelsheim. This is a tremendous stroke of luck, but also a great mystery."

They dated the fossils using the remains of an extinct horse which was found buried in the same spot. In their paper, the scientists describe the canine’s similarities to other remains found in the lower half of the globe, but they still don't have answers to many of the questions the report raises. They plan to continue examining the teeth for clues. The public will also have a chance to see the teeth for themselves, first at a state exhibition this month, and then at Mainz's Natural History Museum.

[h/t Independent]

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6 Pioneering Facts About Mary Leakey

Fossil bones and the earliest footprints of our human ancestors are just a few of Mary Leakey’s groundbreaking discoveries. Get to know the legendary paleoanthropologist, and learn how her serendipitous finds forever altered scientists’ understanding of human origins.

1. MARY LEAKEY WAS A BORN EXPLORER.

Mary Leakey (1913-1996), née Mary Nicol, was destined to be an explorer: Her father, Erskine Nicol, was a landscape painter, and the family traveled extensively through France, Italy, and Switzerland. While staying in a commune in southern France, 12-year-old Mary became interested in archaeology after meeting Elie Peyrony, a French prehistorian excavating a cave. Mary dug through his tiny finds—which included fine points, scrapers, and flint blades—and sorted them into an amateur classification system.

2. FOSSIL HUNTING WAS IN HER BLOOD ...

Leakey’s parents were artists, but hunting for fossils was part of her heritage: Her maternal great-great-grandfather was John Frere, an 18th-century English government official and antiquarian who’s credited with first recognizing Stone Age flint objects as early weapons and tools.

3. ... BUT SHE WASN'T A GREAT STUDENT.

Leakey was intelligent, but she also had a rebellious streak. As a teen, she was expelled from several Roman Catholic convent schools—once for intentionally creating an explosion in a chemistry lab. Figuring she wasn’t cut out for a classroom, Leakey never finished high school, and decided to pursue independent studies in art, geology, and archaeology at the University of London instead. (“I had never passed a single school exam, and clearly never would,” the scientist later wrote in her 1986 autobiography Disclosing the Past.)

4. LEAKEY WAS AN ARTIST WHEN SHE MET HER FUTURE HUSBAND AND RESEARCH PARTNER, LOUIS LEAKEY.

Mary Leakey—who inherited her father’s artistic skills— ended up working as an illustrator for archaeological digs. An archaeologist introduced her to Cambridge University paleontologist Louis Leakey, who needed an illustrator for his book Adam’s Ancestors (1934). The two became lovers, but their union resulted in scandal, as Leakey was still married at the time. The couple married in 1936, after Leakey divorced his first wife.

5. MARY LEAKEY'S FIRST BIG DISCOVERY WAS PROCONSUL AFRICANUS.

Mary Leakey's first major discovery came in 1948 when she found a fossil skull fragment of Proconsul africanus, an ancestor of apes and humans, which later diverged into two separate species. The fossil was thought to be more than 18 million years old.

6. ANOTHER ONE OF MARY LEAKEY'S FAMOUS FINDS CAME COURTESY OF ELEPHANT POOP.

In 1978, Leakey was on an expedition in Laetoli, in Tanzania, when members of her camp engaged in a spirited elephant dung fight. A scientist fell down, and he noticed strange indentations on the ground that had been recently exposed by erosion. They turned out to be tracks made around 3.7 million years prior, from animals that had walked over damp volcanic ash. Examining these prints took several years, but the team's efforts paid off when Leakey noted that one of the prints seemed to be made by a hominin. This discovery showed that early humans began walking upright long before scientists thought they had.

Additional source: Ancestral Passions: The Leakey Family and the Quest for Humankind's Beginnings, Virginia Morell

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