In 2015, scientists announced the discovery of a new Homo species from South Africa, named Homo naledi. Regarded as one of the most primitive Homo species yet unearthed, as its brain was only about the size of an orange, it possessed an unusual mix of human-like and non-human-like features such as feet suited for a life on the ground but hands adapted for a life in the trees. But don’t let its small brain fool you as it was advanced enough to practice death rituals, scientists said. Researchers unearthed fossils from at least 15 individuals belonging to the new species in the Rising Star cave system in South Africa. [Source: Charles Q. Choi, Live Science, September 10, 2015 ||]
Homo naledi lived between 335,000 and 226,000 years ago, about the same time that modern humans first appeared."It's a very exciting finding," said paleoanthropologist Ian Tattersall at the American Museum of Natural History, who suggested these new hominins might not belong to genus Homo. "I'm a great advocate for the notion that the genus Homo has been made overinclusive," he told Live Science. "I don't like to stuff new things in old pigeonholes. I don't think we have the vocabulary needed to describe the diversity we're seeing in early hominins." ||
Charles Q. Choi wrote in Live Science: “The age of the fossils remains uncertain, since the chamber lacks many of the features that scientists normally rely on to date fossils. As such, scientists can't yet say where Homo naledi fits on the human family tree. Depending on its age, it could be a direct ancestor to Homo sapiens, or the ancestor of the species that gave rise to Homo sapiens. "At this stage, all we know is that it's reasonably primitive," Harcourt-Smith said. ||
“The researchers did note that both Homo naledi and the "hobbit" Homo floresiensis had similarly tiny brains. Although the scientists said they could not as yet speculate on any evolutionary links between those two species, the researchers new findings revealed that small-brained, primitive-looking human species with fairly modern features did exist in the past. This suggests that the hobbit is no longer an anomaly, the researchers said.” Scientists detailed their findings online September 10, 2015 in two papers published in the journal eLife and the cover story of the October 2015 issue of National Geographic magazine. ||
Websites and Resources on Hominins and Human Origins: Smithsonian Human Origins Program humanorigins.si.edu ; Institute of Human Origins iho.asu.edu ; Becoming Human University of Arizona site becominghuman.org ; Talk Origins Index talkorigins.org/origins ; Last updated 2006. Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; Wikipedia article on Human Evolution Wikipedia ; Human Evolution Images evolution-textbook.org; Hominin Species talkorigins.org ; Paleoanthropology Links talkorigins.org ; Britannica Human Evolution britannica.com ; Human Evolution handprint.com ; National Geographic Map of Human Migrations genographic.nationalgeographic.com ; Humin Origins Washington State University wsu.edu/gened/learn-modules ; University of California Museum of Anthropology ucmp.berkeley.edu; BBC The evolution of man" bbc.co.uk/sn/prehistoric_life; "Bones, Stones and Genes: The Origin of Modern Humans" (Video lecture series). Howard Hughes Medical Institute.; Human Evolution Timeline ArchaeologyInfo.com ; Walking with Cavemen (BBC) bbc.co.uk/sn/prehistoric_life ; PBS Evolution: Humans pbs.org/wgbh/evolution/humans; PBS: Human Evolution Library www.pbs.org/wgbh/evolution/library; Human Evolution: you try it, from PBS pbs.org/wgbh/aso/tryit/evolution; John Hawks' Anthropology Weblog johnhawks.net/ ; New Scientist: Human Evolution newscientist.com/article-topic/human-evolution; Fossil Sites and Organizations: The Paleoanthropology Society paleoanthro.org; Institute of Human Origins (Don Johanson's organization) iho.asu.edu/; The Leakey Foundation leakeyfoundation.org; The Stone Age Institute stoneageinstitute.org; The Bradshaw Foundation bradshawfoundation.com ; Turkana Basin Institute turkanabasin.org; Koobi Fora Research Project kfrp.com; Maropeng Cradle of Humankind, South Africa maropeng.co.za ; Blombus Cave Project web.archive.org/web; Journals: Journal of Human Evolution journals.elsevier.com/; American Journal of Physical Anthropology onlinelibrary.wiley.com; Evolutionary Anthropology onlinelibrary.wiley.com; Comptes Rendus Palevol journals.elsevier.com/ ; PaleoAnthropology paleoanthro.org.
Discovery of the Homo Naledi Fossils
Charles Q. Choi wrote in Live Science: “Two cavers, Rick Hunter and Steven Tucker, discovered the new fossils in 2013 in a cave known as Rising Star, locatedi n the Cradle of Humankind World Heritage Site about 30 miles (50 kilometers) northwest of Johannesburg in South Africa. The species is named after the cave; "naledi" means "star" in Sesotho, a South African language. [Source: Charles Q. Choi, Live Science, September 10, 2015 ||]
Jamie Shreeve wrote in National Geographic: In 2013, “a pair of recreational cavers entered a cave called Rising Star, some 30 miles northwest of Johannesburg. Rising Star has been a popular draw for cavers since the 1960s, and its filigree of channels and caverns is well mapped. Steven Tucker and Rick Hunter were hoping to find some less trodden passage. In the back of their minds was another mission. In the first half of the 20th century, this region of South Africa produced so many fossils of our early ancestors that it later became known as the Cradle of Humankind. Though the heyday of fossil hunting there was long past, the cavers knew that a scientist in Johannesburg was looking for bones. The odds of happening upon something were remote. But you never know. [Source: Jamie Shreeve, National Geographic, September 2015 /+]
“Deep in the cave, Tucker and Hunter worked their way through a constriction called Superman’s Crawl—because most people can fit through only by holding one arm tightly against the body and extending the other above the head, like the Man of Steel in flight. Crossing a large chamber, they climbed a jagged wall of rock called the Dragon’s Back. At the top they found themselves in a pretty little cavity decorated with stalactites. Hunter got out his video camera, and to remove himself from the frame, Tucker eased himself into a fissure in the cave floor. His foot found a finger of rock, then another below it, then—empty space. Dropping down, he found himself in a narrow, vertical chute, in some places less than eight inches wide. He called to Hunter to follow him. Both men have hyper-slender frames, all bone and wiry muscle. Had their torsos been just a little bigger, they would not have fit in the chute, and what is arguably the most astonishing human fossil discovery in half a century—and undoubtedly the most perplexing—would not have occurred. /+\
“After contorting themselves 40 feet down the narrow chute in the Rising Star cave, Tucker and Rick Hunter had dropped into another pretty chamber, with a cascade of white flowstones in one corner. A passageway led into a larger cavity, about 30 feet long and only a few feet wide, its walls and ceiling a bewilderment of calcite gnarls and jutting flowstone fingers. But it was what was on the floor that drew the two men’s attention. There were bones everywhere. The cavers first thought they must be modern. They weren’t stone heavy, like most fossils, nor were they encased in stone—they were just lying about on the surface, as if someone had tossed them in. They noticed a piece of a lower jaw, with teeth intact; it looked human.
The bones were found in a chamber named Dinaledi (chamber of stars), accessible only through a narrow chute, almost a hundred yards from the cave entrance. How they got there is a mystery. The most plausible answer so far: Bodies were dropped in from above. Hundreds of fossils have been recovered, most excavated from a pit a mere yard square. More fossils surely await./+\
“Berger could see from the photos that the bones did not belong to a modern human being. Certain features, especially those of the jawbone and teeth, were far too primitive. The photos showed more bones waiting to be found; Berger could make out the outline of a partly buried cranium. It seemed likely that the remains represented much of a complete skeleton. He was dumbfounded. In the early hominin fossil record, the number of mostly complete skeletons, including his two from Malapa, could be counted on one hand. And now this. But what was this? How old was it? And how did it get into that cave?/+\
Recovery of the Homo Naledi Fossils
Alyson Krueger wrote in The Guardian: “The remains were uncovered in November 2013 during a three-week expedition, called Rising Star after the local cave system. The chamber where the remains were found is 30 metres below ground, and access is via gaps so small that team members had to extend one arm in front of their bodies, superman-style, to get through. For this reason, the six-strong group was composed of small, slim women, who earned the nickname the underground astronauts.If they had slipped while climbing down the rocks, they could have dropped 20 metres to their deaths. The expedition was so dangerous that a medical team was on hand, with doctors trained to go underground to treat any broken bones. The results were 1,550 bones unearthed, from 15 individuals, more than all previous Africa expeditions combined. [Source: Alyson Krueger, The Guardian, May 25, 2017]
Charles Q. Choi wrote in Live Science: “The fossils were recovered in two missions in 2013 and 2014 dubbed the Rising Star Expeditions. The bones lay in a chamber now named Dinaledi, meaning "many stars," located about 300 feet (90 meters) from the entrance of Rising Star. Getting into Dinaledi required a steep climb up a sharp limestone block called "the Dragon's Back" and then down a narrow crack only 7 inches (18 centimeters) wide. A global call for researchers who could fit through this chute resulted in six women chosen to serve as what the researchers called "underground astronauts." "They risked their lives on a daily basis to recover these extraordinary fossils," study lead author Lee Berger, a paleoanthropologist at the University of the Witwatersrand in Johannesburg, told Live Science. [Source: Charles Q. Choi, Live Science, September 10, 2015 ||]
“The scientists recovered more than 1,550 bones and bone fragments, a small fraction of the fossils believed to remain in the chamber. These represent at least 15 different individuals, including infant, child, adult and elderly specimens. This is the single largest fossil hominin find made yet in Africa. (Hominins include the human lineage and its relatives dating from after the split from the chimpanzee lineage.) "With almost every bone in the body represented multiple times, Homo naledi is already practically the best-known fossil member of our lineage," Berger said. "We will be trying to extract DNA from these fossils," Berger added.” ||
Skinny Individuals Wanted
After Berger the importance of the discovery in Rising Star, he had to figure out how to excavate and retrieve the fossils. Jamie Shreeve wrote in National Geographic: “Most pressing of all: how to get it out again, and quickly, before some other amateurs found their way into that chamber. (It was clear from the arrangement of the bones that someone had already been there, perhaps decades before.) Tucker and Hunter lacked the skills needed to excavate the fossils, and no scientist Berger knew—certainly not himself—had the physique to squeeze through that chute. So Berger put the word out on Facebook: Skinny individuals wanted, with scientific credentials and caving experience; must be “willing to work in cramped quarters.” Within a week and a half he’d heard from nearly 60 applicants. He chose the six most qualified; all were young women. Berger called them his “underground astronauts.” [Source: Jamie Shreeve, National Geographic, September 2015 /+]
“With funding from National Geographic (Berger is also a National Geographic explorer-in-residence), he gathered some 60 scientists and set up an aboveground command center, a science tent, and a small village of sleeping and support tents. Local cavers helped thread two miles of communication and power cables down into the fossil chamber. Whatever was happening there could now be viewed with cameras by Berger and his team in the command center. Marina Elliott, then a graduate student at Simon Fraser University in British Columbia, was the first scientist down the chute. “Looking down into it, I wasn’t sure I’d be OK,” Elliott recalled. “It was like looking into a shark’s mouth. There were fingers and tongues and teeth of rock.”/+\
“Elliott and two colleagues, Becca Peixotto and Hannah Morris, inched their way to the “landing zone” at the bottom, then crouched into the fossil chamber. Working in two-hour shifts with another three-woman crew, they plotted and bagged more than 400 fossils on the surface, then started carefully removing soil around the half-buried skull. There were other bones beneath and around it, densely packed. Over the next several days, while the women probed a square-yard patch around the skull, the other scientists huddled around the video feed in the command center above in a state of near-constant excitement. Berger, dressed in field khakis and a Rising Star Expedition cap, would occasionally repair to the science tent to puzzle over the accumulating bones—until a collective howl of astonishment from the command center brought him rushing back to witness another discovery. It was a glorious time./+\
“The bones were superbly preserved, and from the duplication of body parts, it soon became clear that there was not one skeleton in the cave, but two, then three, then five ... then so many it was hard to keep a clear count. Berger had allotted three weeks for the excavation. By the end of that time, the excavators had removed some 1,200 bones, more than from any other human ancestor site in Africa—and they still hadn’t exhausted the material in just the one square yard around the skull. It took another several days digging in March 2014 before its sediments ran dry, about six inches down./+\
“There were some 1,550 specimens in all, representing at least 15 individuals. Skulls. Jaws. Ribs. Dozens of teeth. A nearly complete foot. A hand, virtually every bone intact, arranged as in life. Minuscule bones of the inner ear. Elderly adults. Juveniles. Infants, identified by their thimble-size vertebrae. Parts of the skeletons looked astonishingly modern. But others were just as astonishingly primitive—in some cases, even more apelike than the australopithecines. “We’ve found a most remarkable creature,” Berger said. His grin went nearly to his ears.” /+\
Analyzing Homo Naledi
Jamie Shreeve wrote in National Geographic: “In paleoanthropology, specimens are traditionally held close to the vest until they can be carefully analyzed and the results published, with full access to them granted only to the discoverer’s closest collaborators. By this protocol, answering the central mystery of the Rising Star find—What is it?—could take years, even decades. Berger wanted the work done and published by the end of the year. In his view everyone in the field should have access to important new information as quickly as possible. And maybe he liked the idea of announcing his find, which might be a new candidate for earliest Homo, in 2014— exactly 50 years after Louis Leakey published his discovery of the reigning first member of our genus, Homo habilis. [Source: Jamie Shreeve, National Geographic, September 2015 /+]
“In any case there was only one way to get the analysis done quickly: Put a lot of eyes on the bones. Along with the 20-odd senior scientists who had helped him evaluate the Malapa skeletons, Berger invited more than 30 young scientists, some with the ink still wet on their Ph.D.’s, to Johannesburg from some 15 countries, for a blitzkrieg fossil fest lasting six weeks. To some older scientists who weren’t involved, putting young people on the front line just to rush the papers into print seemed rash. But for the young people in question, it was “a paleofantasy come true,” said Lucas Delezene, a newly appointed professor at the University of Arkansas. “In grad school you dream of a pile of fossils no one has seen before, and you get to figure it out.”/+\
“The workshop took place in a newly constructed vault at Wits, a windowless room lined with glass-paneled shelves bearing fossils and casts. The analytical teams were divided by body part. The cranial specialists huddled in one corner around a large square table that was covered with skull and jaw fragments and the casts of other well-known fossil skulls. Smaller tables were devoted to hands, feet, long bones, and so on. The air was cool, the atmosphere hushed. Young scientists fiddled with bones and calipers. Berger and his close advisers circulated among them, conferring in low voices./+\
“Delezene’s own fossil pile contained 190 teeth—a critical part of any analysis, since teeth alone are often enough to identify a species. But these teeth weren’t like anything the scientists in the “tooth booth” had ever seen. Some features were astonishingly humanlike—the molar crowns were small, for instance, with five cusps like ours. But the premolar roots were weirdly primitive. “We’re not sure what to make of these,” Delezene said. “It’s crazy.”/+\
“The same schizoid pattern was popping up at the other tables. A fully modern hand sported wackily curved fingers, fit for a creature climbing trees. The shoulders were apish too, and the widely flaring blades of the pelvis were as primitive as Lucy’s—but the bottom of the same pelvis looked like a modern human’s. The leg bones started out shaped like an australopithecine’s but gathered modernity as they descended toward the ground. The feet were virtually indistinguishable from our own./+\ “You could almost draw a line through the hips—primitive above, modern below,” said Steve Churchill, a paleontologist from Duke University. “If you’d found the foot by itself, you’d think some Bushman had died.”/+\
“But then there was the head. Four partial skulls had been found—two were likely male, two female. In their general morphology they clearly looked advanced enough to be called Homo. But the braincases were tiny—a mere 560 cubic centimeters for the males and 465 for the females, far less than H. erectus’s average of 900 cubic centimeters, and well under half the size of our own. A large brain is the sine qua non of humanness, the hallmark of a species that has evolved to live by its wits. These were not human beings. These were pinheads, with some humanlike body parts.” /+\
Homo Naledi Lived 335,000-226,000 Years Ago, Likely Alongside Modern Humans
More fossils of Homo naledi were found in the Rising Star Cave system in South Africa and the previous bones and other artifacts found help dated the species to between 335,000 and 226,000 years ago, pretty much placing them side by side with early modern humans. A series of papers published in the journal eLife addressed many issues related to Homo naledi, chief among them its age, which turned out to much younger than previously thought. [Source: Léa Surugue, International Business Times, May 9, 2017]
Léa Surugue wrote in the International Business Times: “A team led by Paul Dirks from the James Cook University in Australia measured the concentration of radioactive elements and the level of radioactive decay in three fossilised teeth, as well as in the sediments and rocks inside the Dinaledi Chamber – where the fossils were first discovered in 2013-14. This is at present one of the most precise and reliable method for dating samples, made all the more robust here by the fact the scientists had independent laboratories around the world carry the analyses. The experts didn't know which samples came from the cave and which were 'controls'. The findings suggest that H Naledi fossils are between 236,000 and 335,000 years old. This mean that the species might have coincided with the earliest members of our own species – Homo Sapiens – which most likely evolved around that time.
“In a separate study, another team also reports on the discovery of new fossils in a deep chamber of the Rising Star Cave system (nearly 100 metres away from the Dinaledi chamber) – known as the Lesedi Chamber. About 130 fossils were found in the Lesedi chamber, likely belonging to three individuals, one child and two adults. One of the adults is particularly well preserved, with a nearly complete skeleton. It has been called "Neo" – the Sesotho word meaning "a gift". The researchers believe they will find more remains as the excavation progresses.”
Homo Naledi Characteristics
Jamie Shreeve wrote in National Geographic: “ A composite skeleton reveals H. naledi’s overall body plan. Its shoulders, hips, and torso hark back to earlier ancestors, while its lower body shows more humanlike adaptations. The skull and teeth show a mix of traits. “Weird as hell,” paleoanthropologist Fred Grine of the State University of New York at Stony Brook later said. “Tiny little brains stuck on these bodies that weren’t tiny.” The adult males were around five feet tall and a hundred pounds, the females a little shorter and lighter. “The message we’re getting is of an animal right on the cusp of the transition from Australopithecus to Homo,” Berger said....“Everything that is touching the world in a critical way is like us. The other parts retain bits of their primitive past.” [Source: Jamie Shreeve, National Geographic, September 2015 /+]
Charles Q. Choi wrote in Live Science: “On average, Homo naledi stood about 5 feet (1.5 m) tall and weighed about 100 lbs. (45 kilograms). It had a tiny brain, only about 30.5 cubic inches (500 cubic centimeters) in size, making the organ about as large as the average orange. That's smaller than the modern human brain, which is about 73 to 97 cubic inches (1,200 to 1,600 cubic cm), but comparable in size to the brain of Australopithecus sediba. Australopithecines are likely the ancestors of the human lineage. [Source: Charles Q. Choi, Live Science, September 10, 2015 ||]
“Homo nalediwas a surprising blend of primitive and modern hominin traits. For example, "the hands suggest tool-using capabilities," study co-author Tracy Kivell of the University of Kent in England said in a statement. Many scientists have long believed that tool use accompanied a boost in brain size, but Homo naledi's brain was rather small. ||
“In addition, its feet are virtually indistinguishable from those of modern humans. This, together with its long legs, suggest the species was adapted for a life on the ground involving long-distance walking. However,; its fingers were extremely curved, more curved than those of nearly any other species of early hominin, which hints at a life suited for climbing trees. "Modern humans are really unusual in that walking on two legs is pretty much all we do," study co-author Will Harcourt-Smith, a paleoanthropologist at Lehman College in the Bronx and the American Museum of Natural History in New York, told Live Science. "Homo naledi probably spent most of its time walking on two legs, but also spent some proportion of its time up in trees — whether to escape predators or nest at night, we don't know." ||
“Furthermore, Homo naledi's small teeth, slender jaws and many skull features are similar to those of the earliest known members of Homo, but its shoulders are more similar to those of apes. "The combination of anatomical features we see in this creature is not like any we've ever seen before," study co-author John Hawks, a paleoanthropologist at the University of Wisconsin–Madison, told Live Science.”
Homo Naledi Climbed Trees and Walked with a Swagger
Homo naledi, had hands and feet adapted for a life both on the ground and in the trees, which among other things made it walk with a swagger. Charles Q. Choi wrote in Live Science: “Scientists investigated the hands and feet of H. naledi to learn more about a key shift in human evolution — the move from a life of climbing trees to one spent walking on the ground. Modern humans dominate the planet partly because walking upright frees their hands for tool use, scientists have found. The researchers analyzed more than 150 H. naledi hand bones, including a nearly complete adult right hand that was missing just one wrist bone. They found the species shared a long, robust thumb and wrist architecture with modern humans and Neanderthals, potentially giving the hand a precise, forceful grip that may have been useful for tool use. [Source: Charles Q. Choi, Live Science, October 6, 2015]
“However, its fingers were longer and more curved than most australopithecines — indeed, more curved than those of nearly any other species of early hominin. This quality hints at a life suited for moving and climbing through trees. The scientists detailed their findings on H. naledi's hands and feet online in October 6, 2015 in two papers in the journal Nature Communications. "The tool-using features of the H. naledi hand, in combination with its small brain size, has interesting implications for what cognitive requirements might be needed to make and use tools, and, depending on the age of these fossils, who might have made the stone tools that we find in South Africa," Tracy Kivell at the University of Kent in England, lead author of one of the two H. naledi papers, said in a statement.
“The scientists also investigated 107 H. naledi foot bones, including a nearly complete adult right foot. They found the ancient hominin's foot shared many features with the modern human foot, suggesting that it was well-suited for standing and walking on two feet. "The foot is not entirely humanlike, but it's more humanlike than not," William Harcourt-Smith, a paleoanthropologist at Lehman College in the Bronx and the American Museum of Natural History in New York, told Live Science. "I think it would've been very good at walking on the ground."
“However, the H. naledi foot had toes that were more curved than those of modern humans, supporting the notion that the hominin was also relatively adept at life in the trees. "H. naledi wouldn't have been in any way as proficient as chimpanzees or much more primitive hominins at climbing trees, but it still would be better-suited than we are," said Harcourt-Smith, lead author of the other H. naledi paper. [Source: Charles Q. Choi, Live Science, October 6, 2015]
“Intriguingly, H. naledi's pelvis was more like that of australopithecines such as Lucy, flaring outward more than that of modern humans. "This configuration moved the hip muscles away from the hip joints and gave them more leverage in walking — perhaps more of an advantage than humans have today," study co-author Jeremy DeSilva, an anthropologist at Dartmouth University, said in the statement. "Over time, the architecture of the pelvis evolved and expanded to allow the birth of larger-brained babies."These findings suggest that early human evolution involved many experiments "on different ways to be bipedal," Harcourt-Smith said. Scientists are still unsure how exactly H. naledi might have walked differently from modern humans. "But there's absolutely no doubt that its gait would have been different," Harcourt-Smith said.”
Homo Naledi Death Rituals
Charles Q. Choi wrote in Live Science: “Intriguingly, this primitive human species may have disposed of its dead repeatedly, a ritualized behavior previously confirmed only in modern humans. "Homo naledi is a primitive member of our genus, perhaps the most primitive we've ever seen, but it had the capacity both mentally and behaviorally to dispose of remains in a ritual fashion," Berger said. [Source: Charles Q. Choi, Live Science, September 10, 2015 ||]
“Dinaledi is an isolated part of the Rising Star cave system that was never open directly to the surface and attracted only a few accidental visitors. Of the more than 1,550 bones and bone fragments recovered from Dinaledi so far, only about a dozen are not hominin. These include the remains of small animals such as birds and mice. There is no evidence that flowing water or mud washed these bones into Dinaledi, nor are there bite marks suggesting that predators or scavengers carried the remains into the chamber, nor cut marks suggesting cannibalism. Instead, the researchers suggest, these remains were brought into this remote spot intentionally over time. ||
“Prior research had uncovered another possible instance of an extinct human species disposing of its dead, in Atapuerca in Spain. This site also contained remains thrown to the bottom of a cave. "Those hominins were much larger-brained, much closer to modern humans in brain size," Harcourt-Smith said. "There's debate as to which species was at Atapuerca — probably Homo heidelbergensis, a close relative of Neanderthals."
“However, this is the first time such behavior with the dead has been seen with such a primitive hominin— that is, one dating back so early in the human family tree. "It's just an extraordinary discovery, a game-changer to see this very advanced behavior used back then," Harcourt-Smith said. It remains unknown why Homo naledi disposed of its dead in this way. "We can spin a lot of yarns," Harcourt-Smith said. Maybe it buried the dead out of reverence, he said, or "maybe to get rid of things that were smelling. Maybe another species was throwing them down." ||
Later new fossils were found deep in a different chamber of the Rising Star Cave system known as the Lesedi Chamber, about a 100 meters from the Dinaledi chamber. Léa Surugue wrote in the International Business Times: “The scientists note that the Lesedi chamber is small, pitch dark and very difficult to access. This gives credit to the theory that the bodies were deliberately laid to rest inside and that H Naledi was hiding its dead. "The discovery likley adds weight to the hyposthesis that Homo naledi was using dark, remote places to cache its dead," explained John Hawks (Wits University), leader of the research team at Rising Star. "What are the odds of a second, almost identical occurrence happening by chance?" This behaviour may be a sign of the emergence of a primitive culture and suggests that the species may have been more intelligent than was previously hypothesised. [Source: Léa Surugue, International Business Times, May 9, 2017]
Insights from Homo Naledi on Human Evolution
In 2017, the scientific team that found Homo Naledi said that its latest discoveries and insights published in May 2017 in Elife would change the way we look at human evolution. Team leader, paleoanthropologist Lee Berger of Johannesburg’s University of the Witwatersrand, said that it was possible that some artifacts and behaviors attributed only to early humans — things like tools, adornments and burial of the dead — might actually be the work of Homo naledi or some other hominin. The date when Homo naledi lived — 236,000-335,000 years ago — “corresponds with when most archeologists and paleoanthropologists — and genetics — is suggesting we see the rise of modern humans,” he said. “And a lot of people argue that that rise was right here in southern Africa. But now there’s another species here. Everything is very complex from this moment onward.” [Source: Anita Powell, VOA News, May 9, 2017]
Among the cache of fossils found in the second chamber, Berger said was is a nearly complete adult skull, which scientists nicknamed Neo — the SeSotho word for “gift.” “Neo gives us a real look at what the body and face of this incredible new species looks like. It tells us we were a little bit wrong,” he said. “We had guessed there was a little bit more nose. Actually Homo Naledi has a little flatter, even more primitive face than we thought, which is one of the reasons we placed it further back in the family tree of relatedness to early hominins. It’s clear that parts of Homo Naledi from Neo are very, very, very primitive, amongst the most primitive we’ve seen in hominins. And other parts are surprisingly advanced. They, in fact, are comparable mostly with us, as humans.”
Jennifer Raff wrote in The Guardian: “Many people tend to think of human evolution as a very linear path: from primitive creatures more or less directly to ourselves. But for most of the history of evolution, there were multiple species of hominins running (or climbing) around the African landscape, each with their own unique physical adaptations to the challenges of survival. As with all evolutionary experiments, some of these adaptations proved more successful than others. Based on careful study of fossils spanning millions of years in Africa, paleoanthropologists thought they had a good understanding of how the experiment’s results unfolded. Human evolution wasn’t a straight progression by any means, but more like a complicated bush, with branches leading off in many directions. Still, there were definite trends that made their way into our textbooks. Hominin lineages with some trait combinations died off without leaving any descendants. In the lineages that persisted, brains got bigger, legs longer, arms shorter, fingers less curved, teeth smaller. [Source: Jennifer Raff, The Guardian, May 23, 2017]
“It mostly made sense, and the new species discovered in a South African cave in 2015 seemed initially to fit within this paradigm. Homo naledi, as it was called, had some very primitive morphological features that meant it was likely very ancient indeed - possibly 2 million years ago, close to the root of our genus Homo. | “But the recent discovery of a new set of H. naledi remains, in a separate chamber of the same cave system, and the first direct dates of the earlier H. naledi skeletons, has challenged this tidy story. Shockingly, the remains dated to just 236,000-335,000 years ago. This makes H. naledi very young: contemporaneous with early modern H. sapiens elsewhere in Africa. Yet, as the new fossils confirmed, H. naledi possessed a weird mosaic of primitive (ancient) and derived (more human-like) traits, such as small brain sizes (roughly a third of the size as ours: you can see the difference in the picture above) but human-like hands and limbs. |=|
“One reason this has paleoanthropologists in an uproar is that it means some features, such as small brain sizes, persisted long after they thought it possible. Berger et al. suggests that in light of this, we perhaps should be concerned about fossils which we have assigned to species on the basis of morphology rather than direct dates. If some remains have been misclassified, we may need to change our ideas about how different hominin lineages evolved. Another implication of these dates is that these hominins were around South Africa when stone tools began to be made. While they haven’t been found in association with any tools in the cave, we must still be open to the possibility that these small brained hominins could have made them. Finally, whether or not the H. naledi remains were deliberately buried inside the cave remains an extremely contentious issue among paleoanthropologists. These possibilities - both still unverified - pose a “robust challenge” for archaeologists to grapple with.
“Notably, there are some things that these fossils won’t change: 1) We are indeed the product of evolution (I’m anticipating some of the comments on this post inevitably challenging evolution. Sorry guys, the evidence is incontrovertible and the fact that scientists change their minds as to the details when new discoveries are made speaks to the strength of the scientific process, not the weakness of the theory). 2) Humans originated in Africa, 3) There were multiple kinds of hominins co-existing for much of human evolution, 4) Humans are likely descended from H. erectus, with subsequent ancestry from some of the other kinds of hominins (Denisovans, Neanderthals, and probably others). |=|
“So where does H. naledi fit within the overall picture of human evolution in Africa? It’s still unresolved. Berger et al. suggested three scenarios: First, H. naledi belongs to one of the lineages leading to H. habilis, H. rudolfensis, H. floresiensis, and A. sediba. Alternatively, H. naledi is younger - a sister lineage to the clade that contains H. erectus and the big-brained later hominins (including H. sapiens). The final scenario is that H. naledi is even younger still - a sister lineage to H. sapiens. Another possibility is that H. naledi is the result of hybridisation between two or more lineages, perhaps one related to humans and one related to Australopithecines. |=|
“The unusual combination of primitive and derived features of H. naledi make distinguishing between the above scenarios difficult without genetic evidence. If we could get a genome from one or more H. naledi individuals, we could determine the phylogenetic relationship between it and the big-brained hominins: H. sapiens and H. neanderthalensis (we don’t yet know the brain size of Denisovans). This would tell us whether or not human populations had ancestry from this group (and perhaps others). |=|
No Homo Naledi DNA Yet
Despite the recovery of numerous Homo naledi fossils, recovering DNA from them has thus far been elusive.Jennifer Raff wrote in The Guardian: “On a bioarchaeological level (assuming we could get DNA from multiple individuals in the cave), we could ask whether H. naledi individuals buried in the cave were close relatives, and whether there was a relationship between burial location and genetic relatedness. The answers to these questions might give us some insights into the social structure of the species, whether the individuals buried within the cave constituted a single population close in time, or whether there is detectable genetic change over time in the individuals within the cave. We could also use the molecular clock to estimate the time of divergence of H. naledi to the other hominins. [Source: Jennifer Raff, The Guardian, May 23, 2017]
“Ancient DNA could answer a lot of questions regarding H. naledi’s ancestry and relationships, but unfortunately we’re not there yet. While the dates of these fossils fit comfortably within the range at which we can obtain ancient DNA (currently up to ~560–780,000 years ago), Berger et al. notes in their paper that “attempts to obtain aDNA from H. naledi remains have thus far proven unsuccessful.” One of the team members, Dr John Hawks, noted on twitter in a conversation with myself and others that three separate ancient DNA labs have actually made the attempt without any luck (ours at the University of Kansas wasn’t one of them, for the record), but that they will keep trying. |=|
“This is an important reminder of just how difficult and frustrating ancient DNA research can be, and if there’s anything I wish the interested public would know about it, it’s this: Behind the exciting news that comes out every month about this ancient genome or that lie scores of failed attempts, and the frustrated tears of many graduate students. |=|
“Ancient DNA preservation depends on many different variables, such as the temperature(s), UV radiation, and pH the remains have been subjected to, the type of bone, tooth, or tissue being sampled, and the amount of water, salinity, microbes, and oxygen present in the depositional context. This is why some very ancient bones will yield their genetic secrets, while ones just a few hundreds of years old won’t no matter how hard you try. Furthermore, morphological preservation of bone doesn’t always correspond with biomolecular preservation, and we can’t necessarily know in advance whether DNA will be present in a skeleton before we attempt to recover it. Thus ancient DNA researchers must always be mindful about addressing important questions, be responsible about sampling fossils, and not commit too many resources (particularly money and time) to samples which won’t work. Knowing when to stop working on a sample that won’t yield DNA is almost as important as determining which samples to attempt in the first place.
“Will we ever get a H. naledi genome? Based on the hints we’ve gotten so far, the odds don’t look great. Just as with H. floresiensis, the other small-brained hominin that persisted until quite recently (50,000 years ago), their position in our family tree looks to remain unclear for a while - a lesson to us about how much we still have to learn. But if I weren’t relentlessly optimistic, I wouldn’t have lasted long in the world of ancient DNA research. Perhaps it will just take a little more time and luck. We’ve certainly seen these two variables in abundance throughout the remarkable story of H. naledi’s discovery.”
Image Sources: Wikimedia Commons
Text Sources: National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Nature, Scientific American. Live Science, Discover magazine, Discovery News, Natural History magazine, Archaeology magazine, The New Yorker, Time, BBC, The Guardian, Reuters, AP, AFP and various books and other publications.
Last updated September 2018