The Mystery of Homo naledi

A new human species possessing traits of both ancient hominids and modern humans has been found to have lived far more recently than scientists initially believed—pointing to the existence of a “shadow lineage” of primitive humans that may have lived alongside Homo sapiens in southern Africa up until the Middle Stone Age.

In 2013, two spelunkers exploring a cavern near Johannesburg, South Africa stumbled upon a treasure trove of ancient hominid remains. The bones were soon after discovered to be the remains of a previously unknown cousin to humans, and were named Homo naledi, after the Sethoso world for “star.” The hominid, a tiny 5-foot tall species with a brain size and torso shape that resembled early hominids, but with several features (including hand and spinal shape) mirroring modern humans, seemed to fit somewhere between our more ancient ape-like ancestors such as Australopithicus and modern human cousins such as Homo erectus and Homo neanderthales. Because of this, scientists estimated Homo naledi to be somewhere around 2 million years old– but until recently, they didn’t know just how old the species was.

By Chris Stringer, Natural History Museum, United Kingdom

Origins of Homo naledi

In 2015, researchers analyzing the Homo naledi bones found that the remains dated back to some 236,000 to 335,000 years ago, far more recent then expected. This places Homo naledi as living at least until the Middle Stone Age, at which time our own Homo sapiens ancestors were moving into southern Africa (around 200,000 years ago). There’s a strong chance, some scientists say, that the far more primitive Homo naledi may have interacted in the latter part of its existence with Homo sapiens, and that Homo sapiens may even be responsible for the species’ ultimate extinction, outcompeting them in the same way our species is believed to have done with the Neanderthals.

The idea is not without precedent. The species Homo floresiensis, better known as the “Hobbits,” is believed by some scientists to have evolved from early, more primitive human ancestors and surviving unchanged in Indonesia for millions of years after migrating out of Africa. Much like H.naledi, Homo floresiensis is believed to have gone extinct around the time Homo sapiens arrived in its part of the world around 50,000 years ago, driven to the brink by competition with our own species.

Given H. naledi’s ape-like appearance, scientists believe that the species may have initially evolved some 2 million years ago, nearly 1.8 million years before modern humans emerged, then survived in southern Africa nearly unchanged while the Homo genus eventually continued to evolve into Homo habilis, Homo erectus and, eventually, Homo sapiens.

Lee Roger Berger research team

However, Not Everyone Agrees

Other scientists, however, disagree with the idea of Homo naledi surviving unchanged for millions of years, arguing that the bones are far too recent for a hominid from the base of the human tree to have lived until so soon. Instead, they propose that Homo naledi may have evolved from a more anatomically-modern human thousands (instead of millions) of years ago, then later evolved more primitive-like features.

Either way the existence of another human species in southern Africa during the Middle Stone Age means that some of the stone tools uncovered in the region may have been mislabeled as belonging to Homo sapiens, when they could have in fact originated from H.naledi, argues Lee Berger, the lead scientist behind the discovery. However, to date no stone tools have been found with H.naledi bones, although this doesn’t rule out the possibility of the species having tool-making capabilities.

Berger also says that mass the placement of the bodies within the South Africa cave that they were found may point to an early form of ceremonial burial, a claim that has proven controversial. Scientists have counter-argued that the bodies instead may have been deposited in the cave to avoid attracting predators, rather than because of religious significance.

The discovery and aging of H.naledi serves to continue to flesh out the ever-expanding story of our species, which is quickly developing into a complicated web rather than a clear species-by-species progression, full of dead ends, false starts, and species at different evolutionary stages existing at the same time.

For More Information

Images:

  • reconstruction of Homo naledi skull: By Martinvl (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
  • skeletal remains: By Lee Roger Berger research team (http://elifesciences.org/content/4/e09560) [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons
  • skull comparison: By Chris Stringer, Natural History Museum, United Kingdom [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

Article by Devin Windelspecht. Devin is a junior at Northeastern University in Boston MA where he majors in international relations.  Devin is responsible for background work on many of the articles on the site, as well as preparing articles on recent scientific discoveries.

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