Homo Naledi bones rattle evolutionary paradigm

From the bottom of a cave west of Johannesburg, two forms of life are rising from obscurity: Homo Naledi, a puzzling ape; and a new breed of ‘rock star’ palaeo-anthropologist. The potential ‘new species’ could change the evolutionary ‘tree’, or could be just another ape without tools or culture. The eventual results have potential implications for the study of culture.

The stakes in evolution are rising. Fossil ‘detectives’ used to work alone in obscure laboratories, and write papers that only a few hundred of their own kind would read. Now they work in teams, publish blogs with huge followings, sometimes posted with videos and 3D scans in real time, with funding to match.

The latest finds were made in May 2017. Homo Naledi and Prof Lee Berger’s team have been waiting their turn to scramble the theories of evolution. “We were misled. There is no straight line of evolution. We do not yet know how hominid species are connected. We need a complete re-think,” he told Stoneprint Journal. (see a note on the potential implications for the study of culture at the end of the report).

Fossil ‘detectives’ reveal a cache in the Johannesburg Cradle

‘Rock star’ palaeontologist Prof Lee Berger leads a team of 170 scientists in the Cradle of Humankind west of Johannesburg. He had identified likely caves in a review of earlier studies.

Fossils offer windows on the past, thanks to rare geological conditions, as in the West Rand’s Cradle of Humankind area. Berger refused to give up when Richard Leakey and his other mentors told him in East Africa that the evolutionary ‘tree’ was worked out. “They said there were no more species to find”.

But they advised him to go to South Africa and chip away at the likes of ‘Mrs Ples’ in the Sterkfontein cave. In recent years, Prof Ron Clarke and the late Prof Philip Tobias found Little Foot. Then Berger found Homo Naledi skulls at sites named Malapa and Sediba, and the debate about species versus variants of species flared up like a Swartkrans shelter fire on an Ice Age night.

Public interest in our biological past

Berger had long tried blogging to popularise science, and teamed up with John Hawkes to build up a following. Earlier, Australopithicus (Southern Ape Man) Sediba was on the cover of Science three times, and the lay public took an interest.

Then Berger hit the paleo jackpot at Rising Star cave system near Greensleeves. The cave had been known to the local club for 50 years, but had not attracted hominid fossil specialists. Here are many fossil skeletons, often complete, not just teeth and fragments as before.

For the first time, the number of fossil skeletons outnumbered the scientists studying them. There used to be a 1% chance of finding something, like the tooth that Berger found in the West Rand Cradle two weeks after arriving in South Africa 26 years ago. The second tooth he had called “scientific gold that I could build a career on”. But finds and funding dried up. Berger doggedly mapped his finds by GPS and against Google Earth. He discovered that the early data were wrong, and the new data led him to fossil caves.

“At Malapa, it took my young son only 90 seconds to find the first piece of fossil.” The odds improved. Then they hit the fossil ‘lottery’ in Rising Star caves.

Did Homo Naledi meet early modern humans, of whom known records start about BC 100 000, at Klasies River, Border Cave, and elsewhere in Africa? Some critics think people ate ape and monkey brains, and threw the bones down erosion traps, from where a flood or two washed the light bones down, over a gravel trap, to the deepest part of a cave where no large animals ever went (see critic’s warnings against popular evolutionary assumptions below).

Anyone could check the new fossil evidence on the web, or print out exact copies of some of the ‘new’ fossils on a 3D printer. The white plaster fills in some missing parts. “The face looked ape-like, but other skulls now reveal it is flatter and more human-like,” said Prof Berger.

Young speleologists on the team

The scientists hired young West Rand speleologist (cave climber) Rick Hunter, partly because he could fit into the narrow passages leading down to the resting place of the fifteen Naledi skeletons.

“It is a struggle to get through a narrow vertical slit, to the point where the bodies were probably dropped down from, and then another descent and a slope to get to them,” he told Stoneprint Journal.

He saw a jaw, and pointed the lens of a relay camera at it. “I was beyond a beacon placed by a previous caver, but that beacon was not mapped, so I thought it was the skeleton of a climber. But it was partly fossilised, and turned out to be one of the hominids.

The sport cavers who first photographed the bones behind the narrow passage, became involved in the scientific team. Speleologist Rick Hunter helped to map the nooks and crannies of the 1.8km long Rising Star cave system, near the already famous Sterkfontein cave system.

Evolutionary tree, bush, or no relation?

“One hand has bones slightly curved in, as if the body had slowly withered there in the mud.”

Berger jokes that nobody should believe the team’s version of “certain words” that he stuttered when the recovery team brought up the jaw. A link or twig or offshoot in the chain or ‘bush’ of species? There is no firm theory, and thus no firm criticism yet. The entire cache would take many years, perhaps decades, to reveal and study. Most remain in situ for now.

Some of the bones show signs of trauma, perhaps the cause of death, perhaps from falling or being thrown down into the dolomite cave among many earlier bones. Perhaps from eroding in a waste tip near the surface, and washing down in mud.

Unlike the typical jumble of Sterkfontein fossils, the Rising Star finds are more complete, and some are not fossilised yet. And they are much more recent than expected.

There are no signs that these hominids died in the cave, or were pulled into the cave by carnivores, said Rick. Was their inaccessible resting place chosen for being out of reach of carnivores? Or did nature deposit them in the cache by alluvial action?

Did Naledi and our ancestors marry?

Berger and his associate and co-author, Dr John Hawks of Wisconsin, launched their joint book, ‘Homo Naledi’, at Origins Centre in May 2017. “There are no ‘pure’ species. We are mongrels,” said Berger.

Among the responses to the string of new fossils, are some comments that many species include a wide variety of sizes and shapes.

“Some researchers have been too eager to name new species, which may emerge to be variants of known species,” said Prof Francis Thackeray of the Wits Evolution Institute at an open day of lectures in 2016.

The Neanderthals of Europe and the Denisovans of Asia, for example, are known from residues in our genes to have interbred with humans, and thus were human-like.

Lack of tools or artefacts with the bodies in Rising Star caves, could indicate that they were not modern humans, but absence of evidence is not evidence of absence. And tools were probably too heavy to wash across the final hurdle, if the deposit is alluvial.

Could our ancestors have talked to, and perhaps married Homo Naledi in the dolomite hills of Mogale City? Berger replied, “We could not get DNA from the skeletons yet, but we keep on testing new technology.

“We may get lucky again. Palaeontologists are somewhat aggressive and persistent, and the scientific process is speeding up.”

The local cave system resulted from dolomitic geology and groundwater. At Rising Star cave, a rise may have blocked gravel, allowing only light mud and parts of skeletons to spill into the lowest chamber.

Critics warn against popular assumptions

Diane Eager and John Mackay warned against popular assumptions of human ‘ancestors’. Every hominid fossil discovery has been hailed by popular media, and in schools and colleges, as more evidence for the ‘evolution of apes into humans’.

However what was actually found, and thus far concluded, is not clear-cut. “The collection of bones and teeth [used in tentative reconstructions] represents at least 15 individuals. Apart from small hand and foot bones, most of the bones are damaged or eroded.

“Many of the bones are incomplete, and there is not one whole skull or intact cranium. Without one intact whole skeleton as a reference point, there is no evidence these bones belong to one individual, or one species.

“Are the bones evidence for ape to human evolution? No. Fossils are promoted as evidence for evolution only when you fit them into an assumed evolutionary sequence or ‘tree’ of life. Fossils per se by themselves are never evidence for evolution. Comments on the age of these finds by one of the original Homo Naledi research team and other researchers bring this out well.”

Body of evidence, or ape-man of many parts? A tentative reconstruction (after National Geographic) based on a mixture of washed-down bones, that critics say could also be a mixture of several species. Homo Naledi has a name, but not a date yet.

Similar species, such as Australopithecines, such as Lucy, were apes. They are often portrayed as “human ancestors”, but their name means “southern ape”.

Australopithecus Sediba was found in the same region as Homo naledi bones. The shoulders and hips are ape-like, but the wrists, hands and feet are human-like, although the fingers are more curved than human fingers.

Naldi bones have not been dated, so they cannot be fitted into any evolutionary timetable. The estimated age of the famous KNM-ER 1470 skull of Homo Rudolfensis, from Koobi Fora, Kenya, has swung upward and down by more than a half million years as geologists revised age estimates of the KBS Tuff.

The age of the Sterkfontein Member 4 fossils has been notoriously difficult to determine. Different teams have produced very different ages for the famous Little Foot skeleton from the Silberberg Grotto of Sterkfontein, ranging over more than a million years.

Carol Ward of the University of Missouri, commented to The Atlantic: “Without dates, the fossils reveal almost nothing about hominin evolution, beyond supporting the growing realisation that there was much more species diversity than previously thought.”

Species diversity could simply mean more apes. Many apes have become extinct.

At Rising Star cave, there are no whole skeletons and no intact skulls, so formal burial of the dead behind the narrow passage, is unlikely.

Ape and monkey brains were, and still are considered a delicacy in some cultures. The broken skulls and bodies could be food waste, discarded into the upper part of the cave, from where they were washed down during a flood, along with some light mud, leaving stones and gravel behind at turns and inclines.

The bones were not embedded in rock or mineralised like many fossils, but were in “largely unconsolidated mud-rich sediments” in the base of the cave.

If they turn out to be a mixture of human and ape bones, that would also prove nothing, say the critics. Humans and apes live together today, but neither shows any evidence of evolving from one to the other.

“The curious mixture of ape and human characteristics is better explained by the bones being a mixture of human and ape bones, washed into a cave, rather than an ape in the process of turning into a pre-human.”

If human evolution was not the long incremental process that popular culture thinks it was; and if there are no half-human species with semi-cultural behaviour; the case for culture as a standard set of archetypes, in a standard repertoire of media, with a standard ensemble of material artefacts, could be stronger.

  • This report was compiled by Stoneprint Journal, to invite comments on potential evidence for hominid, Neanderthal or Denisovan material culture, such as tools, weapons, art, or ritual; and to invite comment on the application or mis-application of the evolutionary paradigm to material culture. Some prolific Early Stone Age tools are considered to predate most of the hominids.
  • See archetypal analysis of some Ice Age, and Younger Dryas artworks, on http://www.stoneprint.wordpress.com and on http://www.mindprintart.wordpress.com and on http://www.edmondofurter.wordpress.com.
  • Visit Morphosource.org
  • See YouTube videos such as https://www.youtube.com/watch?v=iFn-FgfChGQ
  • Some of the Rising Star fossils are on display at Maropeng, a popular evolution tourist site in the Cradle of Humankind (one of several sites with similar names worldwide).

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