Hominid Hype, Take 2015

When a new species, Homo naledi, was unveiled on September 10, 2015, it was no surprise that news outlets immediately buzzed about the discovery of a new "human ancestor."

What will become of Homo naledi remains to be seen. So far, however, its pathway resembles that of so many other hominin fossils whose “transitional” or “ancestral” status ultimately went belly-up. When evaluating media claims of a “human ancestor,”  a strong dose of healthy skepticism is warranted.

 

The news media might be heavily biased in favor of evolution, but at least they’re predictable. Whenever a new hominin fossil is discovered, reporters eagerly seize the opportunity to evangelize for Darwin. Thus, when a new species, Homo naledi, was unveiled on September 10, 2015, it was no surprise that news outlets immediately buzzed about the discovery of a new “human ancestor.”

CNN declared, “Homo naledi: New species of human ancestor discovered in South Africa.” PBS hailed the discovery of a “Trove of fossils from a long lost human ancestor.” The Daily Mail reported, “Scientists discover skull of new human ancestor Homo Naledi.” NBC New York announced: “Scientists Discover Homo Naledi, Early Human Ancestor.” And so on.

To be sure, the find is striking for its magnitude alone: hundreds of hominin bones were found in a cave near Johannesburg, South Africa. In a field where a single scrap of jaw gets everyone excited, this is a big deal.

Dubious Details

But do we know that Homo naledi really is the “human ancestor” that so many news sources are now promoting? Dig into the details, and the answer comes up “No.”

The main claim about Homo naledi is that it was a small-brained (compared to humans), upright-walking hominin, with a trunk similar to that of the apelike australopithecines, but with humanlike hands and feet. That’s what the media has reported, but the details in the technical papers show that even some of those supposedly humanlike traits are unique:

  • Regarding the hands, the technical papers note the “unique first metacarpal morphology”1; this and other sources indicate that naledihad long, curved fingers, suggesting that, unlike humans, it was well-suited for “climbing and suspension.”2 According to a press statement from the researchers, “the H. naledihand reveals a unique combination of anatomy that has not been found in any other human fossil before.”3
  • Likewise, a technical paper found that its foot “differs from modern humans in having more curved proximal pedal phalanges [i.e., toes], and features suggestive of a reduced medial longitudinal arch,” giving it an overall “unique locomotor repertoire.”4In other words, naledi‘s foot shows that, again unlike humans, it was “likely comfortable climbing trees.”5
  • The technical papers similarly reveal “unique features in the femur and tibia” and a lower limb that “differs from those of all other known hominin.”6
  • Regarding the head, the main technical paper reporting the find states, “Cranial morphology of H. nalediis unique.”7

In other words, overall, the species is highly unique. Lee Berger, the lead scientist who discovered the find, even admitted, “It doesn’t look a lot like us.”8 But the call to evangelize for Darwin is irresistible.

Age Unknown

The discoverers of Homo naledi are calling it an “anatomical mosaic.” That terminology raises a red flag. In the parlance of evolutionary biology, that usually means the fossil is a unique organism that doesn’t fit easily into the standard evolutionary tree. As one technical paper concluded, “the H. naledi skeleton is a unique mosaic previously unknown in the human fossil record.”9

Indeed, just four years ago, the hominin Australopithecus sediba—also discovered and promoted by Berger—was the transitional form du jure between the australopithecines and our own genus, Homo. Yet sediba is very different from naledi in some important ways, including the pelvis. If the same researchers now want to advocate Homo naledi as some new “transitional form,” they must radically revise their evolutionary story.

Both sediba and naledi have been called a “human ancestor” in recent years, but evolutionarily speaking, both claims cannot be true. As one news outlet rightly acknowledged: “Each [sediba and naledi] has different sets of australopith-like and human-like traits that can’t be easily reconciled on the same family tree.”10

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