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Homo naledi: The Basics and The Controversy

The internet, non-scientific publications, religious groups and armchair enthusiasts flew into a frenzy when National Geographic published its October 2015 issue lauding the findings of Lee R. Berger et al., which suggested that modern-day humans (Homo sapiens) did not evolve from apes (Australopithecus) or Neanderthals (Homo neanderthalensis) but from a different ancestor.

For the first time, we decided to sit down, read Berger’s research paper and make the new discovery- and the basic arguments for and against his hypothesis- understandable, so that you can better speak about the subject before getting your panties in a bunch about whether or not your own theories of evolution have been validated.

Modern humans (Homo sapiens) are now the only living species in our genus. Only 100,000 years ago, several other now-extinct species belonged to that genus, and they are referred to collectively as “hominins.”

Paleoanthropologist Lee R. Berger and his team made their discovery in a cave system in South Africa in October 2013 and recovered their samples in just five months. In his report, Berger says he and his team found, buried 98 feet underground, “1,550 hominin specimens representing nearly every element of the skeleton multiple times […] which could be refit into more complete systems. The collection is a morphologically homogeneous sample that can be attributed to no previously–known hominin species.” They named it Homo naledi (“naledi” means “star” in the S. African “Sotho” or “Sethoto” language). The fragments and specimens- were “refit into 737 partial or compete anatomical elements,” in order to complete the system- and were from, not one, but 15 different individuals of different ages, and included teeth and jaw bones. They were clearly hominin, claims Berger. The geological age of the fossils is not yet known.

Berger’s team’s claims1 Homo naledi differs notably from Australopithecus and all known hominids yet described, in the following ways:

  • First metacarpals (toe bones), femora (thigh bones) and teeth
  • Homo naledi’s skull is specifically different from Australopithecus::
    • Pentagonal-shaped, posterior vault
    • External, occipital protuberance
    • Sagittal “keeling” (thickening of frontal or parietal bones) (Sagittal keeling has been found in hominem cranial specimens with turberculosis-related bone infections. Experts have suggested this morphology is synonymous with the spread of TB and the rapid movement of erectus from Africa to Asia [west to east].)
    • Teeth and mandibular features that are smaller and more “gracile” (i.e. slender, without bony crests for heavy chewing muscles, compared to “robust” teeth and jaws for intense chewing on fibrous vegetation) (Earlier studies show a relationship between masticatory power/stress and cranial development. In general, more gracilization in skull size and superstructures follows larger brains and decreased mechanical force of mastication.)2
    • Less post-orbital constriction (larger, more spherical eye sockets)
    • Flatter, squarer face
  • Markedly curved fingers
  • Small body mass- about 88-123 lbs. (similar to small-bodied humans and the largest known australopiths)

Berger summarized: “The overall morphology of H. naledi places it within the genus Homo rather than Australopitheus or other early hominin genera.” “H. naledi presents yet a different combination of traits […] combin[ing] a humanlike body size and stature with an australopith-sized brain; features of the shoulder and hand apparently well-suited for climbing with humanlike hand and wrist adaptations for manipulation; australopith-like hip mechanics with humanlike terrestrial adaptations of the foot and lower limb […] we must abandon the expectation that any small fragment of the anatomy can provide singular insight about the evolutionary relationships of fossil hominins.”

To this point, H. naledi “lacks the powerful mastication that typifies,” but “the generally humanlike ankle and foot” and “aspects of the lower limb suggest enhanced locomotor performance for a striding gait” and “bipedality,” hypothesizes, Berger. He advises that more scientific research is still needed, but that:

“Baboons are no more related to us, than cats are related to dogs. We are both primates, but we don’t descend from baboons. Homo naledi is related to the human species.” (National Geographic Explorer, October 2015)

Not so fast, say skeptics.

Berkeley paleoanthropologist and osteology (bone study) author, Tim White3, has not been shy about his critique of Berger’s work and extrapolations and cites numerous issues, including the following:

  • Berger’s findings are probably S. African erectus
    • 13 of 83 H. naledi skull characteristics are present in H. erectus.
    • Occipital protuberances have been seen in Kenya H. erectus skulls.
  • Berger’s bones have not yet been dated, come from 15 different individuals and evidence of purposeful burial is circumspect at best.
  • Bone scrapings/shavings in photos indicates negligent handling of the specimens.
  • Conspiracy theory: Berger is seeking attention. His naledi paper was published in National Geographic (not a science publication), on the website eLife, and in concert with a NatGeo-sponsored TV special. (White claims that’s just two years from discovery and hardly time for any peer review. White said he, himself, has previously had to “[hold] the popular press off for 10 years,” because “you can’t do good science when those guys are in the room- as Berger did […] while excavating […]”
  • A precedent Berger-NatGeo controversy stirred in 2008 regarding a Palau project, whose hypothesis was dispelled by Berger’s peers. The magazine Nature (in an article by Rex Dalton) additionally alleged that Berger and NatGeo “collaborated with a London production company, Parthenon Entertainment, to make a film of the Palauan finds.”)
  • “The ancestral condition for early modern humans is one of large [cranial] size (in both breadth and length) and robusticity […] a modern cranial ’shape’ appeared before cranial size reduction and gracilization occurred, and a definition of a modern human skull cannot include cranial gracility among its parameters.”2

UH Manoa anthropologist Michael Pietrusewsky, an authority on South Pacific human remains, has said, “The more I read the paper, the more I am convinced it is complete nonsense and cannot be accepted as serious science.”

Whether you believe the hypothesis of H. naledi, or in media-entertainment hype by non-scholars, the discussion is sure to evolve. What is safe to say is that a good dose of humility is needed. As Richard Dawkins told us in The Ancestor’s Tale (The Mouse’s Tale), it is the ordering of- not the complexity of- genes in a genome that manifests a mouse from a man.

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1 Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa. Lee R. Berger, et al., Evolutionary Studies Institute and Centre of Excellence in PalaeoSciences, University of the Witwatersrand, Johannesburg, South Africa. September 10, 2015.

2 The question of robusticity and the relationship between cranial size and shape in Homo sapiens. Marta Mirazon Lahr and Richard V. S. Wright. Journal of Human Evolution, Academic Press, Ltd. (1996).

3 Bones of Contention: Why Cal Paleo Expert is So Skeptical That Homo Naledi Is New Species, by Glen Martin. Cal Alumni UC Berkeley California Magazine, October 1, 2015.)

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