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.”

Stonehenge Builders Likely Descended From Immigrants, Genetic Analysis Says

Matt Cardy/Getty Images
Matt Cardy/Getty Images

There's a lot we don't know about Stonehenge, but until recently, the structure was thought to have been built by hunter-gatherers native to what's considered England today. A new study disputes that theory. As IFL Science reports, Stonehenge was likely the the work of Turkish people who migrated to Britain 6000 years ago and their descendants.

In the new report published in the journal Nature: Ecology & Evolution, scientists from London's Natural History Museum and University College London explain how they analyzed the DNA from the remains of dozens of people who lived in Britain between 8500 BCE and 2500 BCE.

The results contained fewer native British genes than expected: Researchers found that when the people whose bones they studied were alive, most of Britain's hunter-gatherer population had already been replaced by farmers from the Aegean region.

Roughly 6000 years ago, people from what is now Turkey traveled across Europe and settled in Britain. In addition to reshaping the British gene pool, the new group also introduced agriculture to the area. Archaeologists have long debated whether farming is something that was brought to Britain by a different culture or if native hunter-gatherers gradually adopted it on their own.

"The transition to farming marks one of the most important technological innovations in human evolution. It first appeared in Britain around 6000 years ago; prior to that people survived by hunting, fishing and gathering," study co-author Mark Thomas said in a press release. "Our study strongly supports the view that immigrant farmers introduced agriculture into Britain and largely replaced the indigenous hunter-gatherer populations."

That means Stonehenge, the first part of which was constructed around 3000 BCE, was likely the work of people who were culturally and genetically closer to ancient Aegeans than native Britons. But how they moved the 25-ton stones to their current location and for what purpose remains a mystery.

[h/t IFL Science]

An Ancient Shipwreck Has Been Turned Into an Underwater Museum Off the Coast of Greece

iStock.com/ultramarinfoto
iStock.com/ultramarinfoto

If you love ancient history and eerie, abandoned places, it might be time to break out the scuba diving gear and book a flight to Greece. As AFAR reports, the site of an ancient shipwreck near Alonissos, a Greek island in the Aegean Sea, has been turned into an underwater museum.

While underwater museums exist in Florida, Mexico, and Europe, those destinations are geared more toward art and sculpture lovers. In this case, divers will be swimming alongside a piece of history dating back to the late 5th century B.C.E. The wooden cargo ship, which sank for an unknown reason, disintegrated long ago. However, the seabed is still covered in thousands of amphoras (a kind of storage jar used in ancient Greece and Italy), which likely held wine.

Dubbed the Peristera shipwreck, the site was discovered in the early 1990s. It was named after the uninhabited island where it was discovered, but guided dives of the site leave from the harbor of Steni Valla on Alonissos, which is located in the Northern Sporades group of islands in the northwest Aegean Sea.

Peristera is the first shipwreck in Greece to be made accessible to the public, but it won’t be the last. As part of a program funded by the European Commission, the country also plans to open up three other shipwreck sites in the Pagasetic Gulf. The efforts are part of a push to promote eco-friendly tourism while also highlighting the country’s rich history.

“The goal is in the next two years to make the country’s shipwrecks visitable, but also to provide important information and raise awareness about underwater monuments, such as the Peristera wreck off Alonissos,” alternate culture minister Kostas Stratis said at an event, according to the Greek City Times.

Italy and Croatia are also expected to create their own underwater museums in the future via the same program, called BlueMed.

[h/t AFAR]

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