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Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
Hawks et al. in eLife, 2017

Puzzling Human Relative Homo Naledi May Have Lived at the Same Time as Our Ancestors

Original image
Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
Hawks et al. in eLife, 2017

It's tempting to think that evolution works in a straight line, with clearly defined, graduated steps from primitive to modern. We humans are especially prone to telling our own evolutionary story in this manner. Evolution doesn't work that way, though, and we aren’t even the end point of human evolution, but works in progress. (Personally, I hope we are amphibious and have fins in 3 million years. That would be awesome.)

The latest evidence for that essential truth comes from the Rising Star cave system in South Africa, where scientists say Homo naledi, the unusual hominid species they discovered there in 2013, is surprisingly young, living as recently as 236,000 years ago. That means it was one of various hominids wandering the Earth at the same time as the Neanderthals in Europe; the Denisovans in western Asia; the ancestors of the “hobbit,” Homo floresiensis; and, in Africa, potentially alongside the earliest members of our own species, Homo sapiens.

Moreover, the researchers found three more individuals in another chamber in the cave system, one of them with the most complete H. naledi skull discovered yet. (You can see it above.) Today the large team of researchers published a trio of papers documenting their results in the open-access journal eLife.

In 2015, we reported on the initial discovery of 15 sets of hominid remains found in the Dinaledi cave by a team of researchers led by paleoanthropologist Lee Berger. It was an unprecedented bounty of bones. Often, paleoanthropologists are reconstructing human evolutionary history from scant remains—a fragment of skull or jaw bone here, a femur or a finger there. But in the Dinaledi cave, there are at least 1500 bones, and likely a lot more, since only a small fraction of the cave was excavated by a half-dozen archaeologists—all female, all cavers, all slim enough to squeeze through a series of cave tunnels that narrowed to just 7 inches in one spot—who worked in extraordinary conditions to excavate the bones from a pitch-black cave nearly 100 feet beneath the surface.

The ancient creatures were no bigger than the small but formidable women who unearthed them. Slender and about 5 feet tall as adults, they would’ve weighed just under 100 pounds. Their bodies are a fascinating mosaic of primitive and modern: tiny, orange-sized brains housed in skulls with jaws and teeth closer to early Homo; shoulders suited for climbing trees but feet and ankles made for walking; hands potentially capable of making tools, but with fingers well-curved for tightly gripping tree branches.

The discovery made headlines worldwide. Most of us—whether scientist or science nerd—fascinated by the find had one question: How old were they?

DATING THE REMAINS

When H. naledi was first discovered, the researchers deliberately didn’t attempt to answer that question. Determining where a species fits into the evolutionary record based on its morphology is not an unusual approach, but it can also be misleading. In the past 1.5 years, other scientists have proposed ages for H. naledi that range from 100,000 to 2 million years ago.

In one of the current studies, researchers led by James Cook University geologist Paul Dirks conducted six dating tests to narrow the age range, including the paleomagnetic dating of calcite left behind by running water and a chemical analysis of three fossil teeth discovered in the cave using a technique called combined U-series and electron spin resonance (US-ESR) dating. From all the tests, they came up with an age range: they're most likely between 236,000 and 335,000 years old.

As eLife notes in a commentary on the study, “The estimated dates are much more recent than many had predicted, and mean that H. naledi was alive at the same time as the earliest members of our own species—which most likely evolved between 300,000 and 200,000 years ago. These new findings demonstrate why it can be unwise to try to predict the age of a fossil based only on its appearance, and emphasize the importance of dating specimens via independent tests.”

American Museum of Natural History paleoanthropologist Ian Tattersall echoed that sentiment to Mental Floss. “This is an object lesson in trying to date anything by what it looks like,” he says. While he doesn't find the age estimate surprising, he’s less convinced that H. naledi belongs in our Homo genus: “Anything as odd as this is always going to be tough to fit into both a phylogeny and a timescale,” he notes.

Did our ancestors interact with this oddball? We have no idea. But we do know that the picture of human evolution continues to expand in detail and complexity with every discovery like H. naledi.

Bioarchaeologist (and regular Mental Floss contributor) Kristina Killgrove, who teaches biological anthropology, human origins, and evolutionary theory at the University of West Florida, tells us that the long wait for H. naledi dates was “worth it.”

She says, “These dates reveal a much more complicated story of hominin evolution than ever before. We used to think of human evolution as a single lineage—the classic image of the progression from apes to humans. But H. naledi shows that palaeoanthropologists are onto something far more complex—and far more interesting! While these new dates won't make it into textbooks in time for the fall semester, I will certainly be updating my human evolution lectures this summer."

ONE NEW CAVE, THREE NEW BODIES

Whatever we have to learn about this cousin of humanity can only be helped by the other discovery reported today in eLife: 133 bones from three likely H. naledi individuals—two adults and one child—found in another cave in the Rising Star system. First spotted in 2013 by cavers, the bones were unearthed in three locations in a cave the researchers coined Lesedi. The two caves are found at the same depth, but they’re not directly connected.

As with the first expedition into the Dinaledi cave, the working conditions for the researchers weren’t easy: Wits University archaeologist Marina Elliott, who led the intrepid team of “underground astronauts” who excavated both sites, told National Geographic that while the Lesedi cave was slightly easier to reach than Dinaledi, she still had to excavate one set of remains from a 2-foot-wide alcove while laying on her chest, her shoulders pinned between rocks. “It’s extremely physically difficult,” she said. “I’ve tried to do a lot of yoga to get myself to be able to do it.”

Elliott would probably say it was worth it, though; the remains she excavated in that location yielded the most complete H. naledi skull so far discovered. Dubbed Neo (after the Setswana word for "a gift," not the The Matrix character), this adult has a larger skull—and therefore a larger brain capacity—than the other specimens so far discovered, but it falls within an expected range.

ARE THESE BURIALS OF A SORT?

One of the most contentious theories Berger and the team proposed when the first H. naledi fossils were discovered was that these bodies had been intentionally placed in the cave in some sort of death ritual. Berger and John Hawks, a paleoanthropologist at the University of Wisconsin, revisit that theory in the third paper published in eLife. They point out that the caves are difficult to access and aren’t obvious “death traps” that individuals could’ve accidentally fallen into. Nor did the remains show any signs of mass death, having been fed upon by carnivores or scavengers, or of having been flushed into the caves by a water system.

So how did they get there?

The researchers write, “We propose that funerary caching by H. naledi is a reasonable explanation for the presence of remains in the Dinaledi and Lesedi Chambers. Mortuary behaviors, while culturally diverse, are universal among modern human cultural groups. Such behaviors are not seen in living non-human primates or in other social mammals, but many social mammals exhibit signs of grief, distress, or other emotional response when other individuals within their social group die.”

They say that while there’s no evidence of symbolic thinking among H. naledi, such sophisticated thought isn’t necessarily a requirement for a death ritual. The “physical and social effects of the deaths of group members” could have been motivation enough.

“Such behavior may have many different motivations, from the removal of decaying bodies from habitation areas, to the prevention of scavenger activity, to social bonding, which are not mutually exclusive,” they note. “We suggest only that such cultural behavior may have been within the capabilities of a species that otherwise presents every appearance of technical and subsistence strategies that were common across the genus Homo.”

Original image
Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
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Stones, Bones, and Wrecks
9-Year-Old Boy Trips Over the Bones of a Long-Extinct Elephant Relative
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A 9-year-old boy quite literally stumbled across a new paleontological discovery when he tripped over a giant skull while hiking in Las Cruces, New Mexico in November 2016. As The New York Times reports, the fossilized bones have been identified as the million-year-old remains of a Stegomastodon, a long-extinct distant relative of the modern elephant.

It all began with a game of chase: Jude Sparks, now 10, was running from his younger brothers when he tumbled face-first over what appeared to be a giant tusk. "My face landed next to the bottom jaw," Sparks told ABC news affiliate KVIA-TV. "I look farther up and there was another tusk."

Sparks's parents thought it looked like an elephant skull; his brother, a cow skull. As for Jude himself, he eyed the oddly shaped bones, and "just knew it was not something that you usually find," he later told the Times.

The Sparks didn't dig up the bones, but they did take a cell phone picture. Later, they compared the snapshot to elephant skulls, but they weren't 100 percent identical. So to solve the mystery once and for all, the family sought the opinion of Peter Houde, a biology professor at New Mexico State University.

Houde instantly recognized the skull as that of a Stegomastodon, a creature that belonged to the animal family Gomphotheres and is a distant cousin of ancient mammoths and modern elephants. Stegomastodons roamed the Earth in the past few million years, and may have been hunted by early humans. This particular specimen is at least 1.2 million years old. Theories for the Stegomastodon's extinction include climate change or the arrival of mammoths, which may have led to a competition for food resources, according to National Geographic.

Mammoth fossils are relatively common across the western portion of North America, but only a couple hundred Stegomastadons have been found throughout the world. The Sparks had serendipity on their side, as they visited the site right after heavy rains had exposed the Stegomastodon skull.

Together, Houde and the Sparks family reburied the skull and sought permission from the landowner to excavate the find. Once they obtained a team, a permit, and funding, they got to work and dug up the skull in May.

"All of the protein is gone from these fossils, and the bone is very, very brittle and fragile," Houde told KVIA. "And as soon as the sediment is taken away from around it, it just falls apart completely on its own. So we have to use preservatives to stabilize it before we remove the sediment around it. And then build plaster and wooden casing around it to remove it safely. It's a big job."

The Stegomastodon will likely go on display at New Mexico State University, providing students, faculty, and visitors alike with an up-close view of the rare fossil.

[h/t The New York Times]

Original image
Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
iStock
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Stones, Bones, and Wrecks
Melting Glacier Reveals Bodies of Swiss Couple Missing Since 1942
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On August 15, 1942, Marcelin and Francine Dumoulin ventured to the meadow above their house in the Swiss Alps to milk their cows. What should have been business as usual turned into a harrowing missing-persons case when the married couple never returned. Now, nearly 75 years later, two frozen bodies that likely belonged to Marcelin and Francine have been found in the dwindling Tsanfleuron glacier near their former home, Reuters reports.

An employee at the Les Diablerets resort in Switzerland's Valais canton saw the remains near a ski lift earlier in July. The bodies, one male and female, were perfectly preserved down to their belongings and 1940s attire. Experts believe the couple perished after falling into a crevasse. Like other Alpine glaciers, the Tsanfleuron glacier has been hit hard by rising temperatures associated with climate change. The glacier finally revealed the missing bodies this summer after years of receding.

When Marcelin and Francine vanished, they left behind seven children who never gave up hope of finding them. Seventy-nine-year-old Marceline Udry-Dumoulin, the couple’s youngest child, told a local newspaper the discovery brings her a "deep sense of calm."

The bodies will now undergo DNA testing to verify their identities. Once that's taken care of, Udry-Dumoulin plans to give her parents "the funeral they deserved."

[h/t Reuters]

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