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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.
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

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.
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.”

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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.
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Stones, Bones, and Wrecks
Take a Closer Look at the $17 Billion 'Holy Grail of Shipwrecks'

Feast your eyes on these new images of the treasure among the wreckage of the Spanish ship San José, often called the "holy grail of shipwrecks." When it sank on June 8, 1708, it was carrying gold, silver, jewels, and other precious cargo worth roughly $17 billion today. Now, Woods Hole Oceanographic Institution (WHOI) is revealing the major role it played in the 2015 expedition to find the San José.

The three-masted, 62-gun Spanish galleon exploded and sank at the hands of the British during the War of the Spanish Succession. It was carrying its riches to the Colombian city of Cartegena to finance the war. Archaeologists had been trying to find the San José for decades before it was finally located on November 27, 2015, during an expedition organized by Colombia, Maritime Archaeology Consultants (MAC), and WHOI. The multibillion-dollar treasure, which still sits nearly 2000 feet below the surface of the ocean near Cartegena, is just now being revealed.

WHOI's autonomous underwater vehicle REMUS 6000 was responsible for finding the elusive wreck. REMUS has been with the project since the beginning: The machine created the first side-scan sonar images of the site. After that, REMUS journeyed to a point 30 feet above the site and captured high-resolution photos of the ship's distinctive bronze cannons, which are engraved with dolphins. REMUS's documentation of this defining feature allowed scientists to positively identify the wreck as the fabled San José. (Thanks to whoever had the idea to put dolphins on the cannon in the first place.)

WHOI also released REMUS's photos of the wreckage, which show details of the horde, including ceramics and those famous cannons. "This constitutes one of the greatest—if not the biggest, as some say—discoveries of submerged patrimony in the history of mankind,” Colombian president Juan Manuel Santos said back when the treasure was discovered.

The San José's treasure is the subject of a legal battle for ownership between Colombia and U.S. salvage company Sea Search Armada, which helped look for the wreck. In 2011, four years before the San José was even found, the court ruled that the booty belongs to Colombia, but the dispute is ongoing. Because of the legal drama, the exact location of the wreck remains a government secret.

Below, check out the newly released pictures for a closer look at cannons, teacups, and other ceramics.

cannons from the San Jose
Woods Hole Oceanographic Institution

pots from the San Jose
Woods Hole Oceanographic Institution

teacups from the San Jose
Woods Hole Oceanographic Institution

REMUS 6000
REMUS 6000
Mike Purcell, Woods Hole Oceanographic Institution


A mosaic of images taken by the REMUS 6000 depicts the whole site.
A mosaic of images taken by the REMUS 6000 depicts the whole site.
Jeff Kaeli, Woods Hole Oceanographic Institution

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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.
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Stones, Bones, and Wrecks
Researchers Accidentally Discover 128-Year-Old Shipwreck
iStock
iStock

Scientists conducting a routine survey of the waters along Australia's east coast got more than they bargained for when they accidentally discovered a 128-year-old shipwreck.

Their encounter with the sunken Carlisle, which sank in 1890, was captured on camera, and Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) has released footage showing an aerial view of the wreckage, teeming with schools of fish.

The researchers were mapping the seafloor of Bass Strait, which separates mainland Australia from the island of Tasmania, to improve nautical charts for the major shipping route, according to Mashable. During a scan of the waters, the sunken ship showed up as a "blip," ABC reports.

"We just happened to go over this blip, and we noticed it, and thought, 'Oh jeez, that looks just a little too much like a shipwreck,' and so we did a little bit more investigating and looked at it digitally," CSIRO hydrographer Matt Boyd told ABC. "Then once we established that yes, it was a shipwreck, we put a drop camera down."

Volunteers from the Maritime Archaeological Association of Victoria then went to the site and confirmed that the ship was indeed the Carlisle. It most likely collided with rocks while sailing from Melbourne to Newcastle, where it was supposed to pick up coal on its way to South America. All 23 crew members survived, escaping on three life boats.

The researchers discovered two more shipwrecks during a weeklong expedition from Brisbane to Hobart, one of which was identified as the HMAS Pioneer, a ship built for the British Royal Navy in 1900 that was scuttled in 1931.

[h/t ABC]

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