How Intelligent Was Homo naledi?

Discover Magazine (and other outlets) are running a story which questions how important cranial size is to overall intelligence.  The focus of this inquiry is Homo naledi, the small-brained hominin that is now thought to be no more than 200ky old.  Lee Berger, who was on the team that discovered Homo naledi has always argued that, because of the comparative difficulty of navigating the cave, that she was placed in the Rising Star Chamber intentionally.  At issue is the brain size:

When it comes to brain volume, previous research established that Homo naledi‘s was 465-560 milliliters. (In today’s study, the authors acknowledge those earlier numbers, based on virtual reconstructions, but also perform their own physical reconstructions and measure the volume with a water displacement method, arriving at a similar range of 460-555 mL.)

This is very small. As the authors note, contemporary hominins possessed brains well over 1000 cc at this point. It was the complexity of H. naledi's brain that surprised people:

Homo naledi‘s inferior frontal and lateral orbital gyri were organized notably more like that of other members of the genus Homo than that of australopiths. These are parts of the brain associated with complex behaviors, such as communication, planning and tool-making, that are particularly important in our lineage.

Finding Homo naledi‘s brain was structurally similar to that of larger-brained members of the genus tells us two important things. First, it means Homo naledi itself was likely capable of more complex behavior than australopiths with a similar brain volume but different brain structure. Second, it torpedoes the old notion that Homo brains grew steadily in size and complexity until reaching the evolutionary pinnacle that is Homo sapiens (/sarcasm, just a touch).

As we discover that early Homo was behaviorally more complex than we thought, it also forces us to rethink what went on later in hominin evolution and re-evaluate evidence of complexity in H. erectus and archaic H. sapiens. 
 

Why Is Homo floresiensis Still Such a Mystery?

Cosmos Magazine has an article by Debbie Argue, biological anthropologist from Australian National University, about Homo floresiensis and why it has been a struggle to accurately and adequately place this hominin within the framework of human evolution.

 Here was the initial assessment:

Peter Brown and colleagues originally proposed two competing hypotheses about the origins of H. floresiensis. One is that the species is an early hominin similar to the earliest identified in the Homo genus. The fossils for these species are known only from Africa and are between one and two million years old. This implies that the ancestors of H. floresiensis could have got to Flores Island in the vicinity of a million years ago and survived there until at least 60,000 years ago.

Their alternative hypothesis was that H. floresiensis is a dwarfed descendant of Homo erectus, which is the only known non-sapiens hominin to once have existed in Indonesia. Its remains have been found on the island of Java. According to this view, the dwarfing of H. erectus was an evolutionary response to being isolated on an island with a limited food supply. Just as the Asian elephant evolved into the dwarfed Flores stegodon after becoming marooned on the island, H. erectus could have met a similar fate.

It was also proposed that this hominin might have expressed microcephaly.  This idea failed to explain other aspects of the skeleton, however, such as its diminutive height (around 3 feet), long arms and feet and primitive skull features. Here is an image of H. floresiensis compared to a modern human, who had been running around the landscape for at least 100k years while H. floresiensis was extant.

This all saw at least some resolution with the discovery and description of some remains  on another areas of the island Flores that were very similar to the H. floresiensis remains but dated to some 600 thousand years earlier than the remains in Liang Bu.  This lent more credence to the idea that H. floresiensis was, in fact, an offshoot of Homo erectus.

So, Argue, along with Colin Groves, Bill Jungers and Mike Lee, performed statistical tests (this story does not say which kind, a peculiar omission) on a number of different hominin species, comparing them to H. floresiensis.  What did they find?

We therefore hypothesise that H. floresiensis shared a common ancestor with H. habilis. We do not know who that ancestor was or when it lived, but it would have to be older than the oldest H. habilis specimen known, so older than 1.75 million years. The implication is that the H. floresiensis ancestor evolved before that time in Africa, dispersed from that continent, and arrived on Flores earlier than 700,000 years ago, judging by the age of the jaw and teeth found at Soa Basin. This represents a hitherto unknown movement of very early hominins out of Africa.

Presently, the earliest evidence for hominins outside of Africa come from Europe, the Near East and Asia, and date to between 1.5 and 1.8 million years ago. Argue's hypothesis would suggest that H. floresiensis appearance in east Asia represents a separate migration out of African sometime either before or after the wave that saw Homo erectus show up in Trinil and Sangiran, in Indonesia.

Questions still abound as to why this species never saw the evolutionary trajectory that other hominins went through in terms of cranial expansion, increase in height and changes in brachial and crural indices. On the other hand, if evolution proceeds through what we have termed systematics, then advanced traits will show up in related species and if the ancestors of H. floresiensis were cut off, they would just go on their merry way.  We know that such a pattern holds for H. naledi, in South Africa, which coexisted with archaic Homo sapiens, in some way, shape or form. 

The article ends on a very peculiar note, in which she suggests the remote possibility that H. floresiensis is still alive out there, somewhere:

Could the Hobbit still exist in the wild mountain forests of Flores? When H. floresiensis was announced, the media picked up on the local folklore that small human-like creatures roam the forests. Descriptions of sightings are well recorded and quite detailed. The similarity to H. floresiensis is intriguing. But most researchers would say ‘show me the bones!’

This reminds one of the stories involving the Yeti/Sasquatch/Abominable Snowman, which likely derive from the finding of the bones of the Miocene ape Gigantopithecus, which was close to ten feet tall, when standing.  Is H. floresiensis still out there?  Probably not, but I am sure that the cryptozoologists haven't given up hope. 

Q&A With Lee Berger on Human Evolution

The Sunday Times has an interview with Lee Berger about human evolution, in advance of his new book, co-written with John Hawks, Almost Human: The Astonishing Tale of Homo naledi and the Discovery That Changed Our Human Story. As was reported earlier, the original fossils were undated but appeared to be reflective of an early stage in the development of Homo. This idea was shattered when new dates were derived.  As I wrote at the time:

Homo naledi, however, was missing a date—until recently. Nearly everyone in the scientific community thought that the date of the Homo naledi fossils, when calculated, would fall within the same general time period as other primitive early Homo remains. We were wrong. The radiometric dates—recorded using several methods carried out at different laboratories—yielded almost identical ages of between 236 and 300 thousand years before the present (BP). This was an order of magnitude younger than we expected. To say we were surprised would be an understatement.

Interestingly, the interviewer asks no important questions about Homo naledi or the Dinaledi Star cave, itself.  Amid all of the sturm und drang of his tortuous relationships with Ron Clarke and Philip Tobias (✟ 2012), there is one interesting question about human evolution in general:

Throughout the final chapters of the book you often mention how much there still is to learn about Homo naledi and that it’s very likely that there are more early hominim species which are yet to be discovered. The skeletal material you recently came across in the Lesedi Chamber shares similarities with Homo naledi and adds to this statement. What can/does this new discovery tell us about human evolution in Africa?

I think the clear picture that has come from both the discovery of Australopithecus sediba and Homo naledi is that the story of human evolution is not a simple, linear, straightforward one but that ours is a complex history. Naledi and sediba show us that there is more to be found – it’s clear that we don’t really know their ancestral history and the few fossils of other species found across Africa don’t help us much with interpreting where they fit in our family tree – and that’s exciting. We currently are back in the Dinaledi and Lesedi Chambers and making new discoveries – particularly exciting is we seem to have strong evidence that Homo naledi did indeed come down the narrow chute the way our “underground astronauts” come – and that is wonderful and hard to explain – but it’s exciting!

This has been a contentious issue: whether or not the fossil remains were “placed” there or were brought in by scavengers. What is also not clear is if the book was published before the new dates became available, or not.  I will have to buy the book to find that out.  While the rest of the interview is a tad unsubstantive, it is interesting.

New BioLogos Post: What Homo Naledi Means for the Study of Human Evolution

I have a new post up on the significance of the Homo naledi dates and how they affect the study of human evolution.  Comments welcome there and here.

New Post on Homo naledi From Darrel Falk and Deb Haarsma

Darrel Falk and Deb Haarsma have teamed up on a new post about the peculiar South African hominin, Homo naledi, a find on which I reported a few days back.  Darrel Falk:

This is a wonderful time to be studying human origins. Scholars used to think that there was a slow steady progression of one single species after another becoming more and more human-like through time. That’s not the way it was at all. Although these fossils give no evidence for when H. naledi went extinct, it’s clear it was our contemporary in Africa for at least a little while. There also were at least several other hominin species outside of Africa at that same time. Some members of our species migrated out of Africa to Eurasia about 70,000 years ago, only to find that Homo neanderthalensis and the related, but distinctive Denisovans were already there. At the same time, the primitive diminutive species, H. florisiensis, occupied an island in Indonesia, and H. erectus was in eastern Asia. Meanwhile, back in Africa, we know from genetic evidence that, in addition to H. naledi, another unknown hominin species was present and interbred with our species as recently as 30,000 years ago. So our lineage shared life on this planet with a whole set of other species up until just a few thousand generations ago.

A bit back, I wrote a BioLogos post where I examined the hominin diversity in the early to middle Pleistocene, in which I asked the question How Many Forms Were There?  In that post, I pointed out that our simplistic notions of hominin taxonomy needed to be seriously re-evaluated. Where we once upon a time thought that there was only one species of hominin between 3 and 3.5 million years ago, there may, in fact, have been anywhere from three to five.  It is becoming more likely that this is a pattern that characterizes human evolution, perhaps, all the way up to the ascendancy of modern humans.  If this is so, then Bernard Wood is correct, in that we have many, many more species throughout the range of human evolution than we thought.  This discovery will cause a radical rethink of how we interpret species in the human fossil record.  Witness the rise of systematics.

Surprising New Information About Homo naledi

The Atlantic (and other outlets) has a story on new information on the date of the Homo naledi fossils from Rising Star Cave and it is...surprising.  As Sarah Zhang writes:

The one thing everyone agrees is that the fossils themselves are spectacular. In 2015, researchers unveiled 1,500 hominin fossils found deep in a South African cave, excavated by six cavers who were all skinny, short, and female. The hominin, a new species the team christened Homo naledi, was an unusual mix of the old and modern. Their heads were small, suggesting an early hominin perhaps more than a million years old. But their feet were stiff for walking upright and their hands adept like modern humans.

So in the media frenzy that followed—a National Geographic cover, a documentary, numerous articles—the question kept coming up: How old are these Homo naledi fossils, really? What do they tell us, if anything, about the origin of Homo sapiens?

To that first question, the researchers now have an answer: 236,000 to 335,000 years old. As for the second question, well, it’s complicated. “You can’t tell simple stories anymore,” says Lee Berger, a paleoanthropologist at the University of the Witwatersrand who led the research. “This is the gigantic message out of Homo naledi.” The age of these fossils puts these strange, small-brained yet human-like hominins in South Africa just before the emergence of the first anatomically modern Homo sapiens.

Holy Liang Bua, Batman!  If the bones really are 236k, then that would put them roughly 40-50 k years before the advent of modernity represented by the Omo 1 cranium.  Admittedly, that skull is fragments “swimming in plaster” but we have a pretty good idea of what it looks like. We certainly have modernity in the Bouri remains from Herto at 160 ky.

How do we know how old the fossil are?  From the eLife article:

Now, Dirks et al. – who include many of the researchers who were involved in the discovery of H. naledi – report that the fossils are most likely between 236,000 and 335,000 years old. These dates are based on measuring the concentration of radioactive elements, and the damage caused by these elements (which accumulates over time), in three fossilized teeth, plus surrounding rock and sediments from the cave chamber. Importantly, the most crucial tests were carried out at independent laboratories around the world, and the scientists conducted the tests without knowing the results of the other laboratories. Dirks et al. took these extra steps to make sure that the results obtained were reproducible and unbiased.

More specifically, they did Electron Spin Resonance (or Electron Paramagnetic Resonance), Uranium-Thorium disequilibrium, Optically Stimulated Resonance and radiocarbon dating.  This is probably not the last word on the dating of the fossils and there are quite a few assumptions that have been made regarding the provenance of the fossils to the cave sediments, but this is the closest thing that we currently have. One of the critical problems in dating much of the South African cave deposits is their relationship to the hominins found there.  Often, the caves opened up at the top and the fossil remains either fell in, were dropped in or they crawled in.  What makes the Rising Star remains so peculiar is that this cave did not form in the traditional way and the bones were so far into the cave. 

Where does this leave us? It leaves us with more questions than answers.  It has been common consensus that, while there was considerable variability in hominin morphology throughout the Pliocene and early to middle Pleistocene, that this "settled down" and that variability diminished as we made the transition to modern humans.  These fossils suggest the opposite: that large amounts of variability were, in fact, present throughout the range of human existence and only recently (200ky to the present) did this variability drop off.

I am quite sure that more studies will be done to elucidate the relationship that these fossils (there are more very similar fossils next door in the Lesedi cave complex) have to other forms in Africa.  There are obviously very peculiar cultural interactions going on, though (or lack, thereof).  With the Liang Bua remains in East Asia, hypotheses of endemic dwarfism and isolation have been put forth to explain why these remains are so diminutive and primitive.  It is more difficult to put forth these same arguments here where there are few to no barriers to migration and interaction between groups. 

New Study on Homo naledi

Lauren Schroeder and colleagues have published a report on the skull of Homo naledi, in which they address the characteristics and attempt to place them in a taxonomic context, using morphometric analysis.  From the abstract:

Our results indicate that, cranially, H. naledi aligns with members of the genus Homo, with closest affiliations to H. erectus. The mandibular results are less clear; H. naledi closely associates with a number of taxa, including some australopiths. However, results also show that although H. naledi shares similarities with H. erectus, some distances from this taxon – especially small-brained members of this taxon – are extreme. The neighbor joining trees place H. naledi firmly within Homo. The trees based on cranial morphology again indicate a close relationship between H. naledi and H. erectus, whereas the mandibular tree places H. naledi closer to basal Homo, suggesting a deeper antiquity. Altogether, these results emphasize the unique combination of features (H. erectus-like cranium, less derived mandible) defining H. naledi. Our results also highlight the variability within Homo, calling for a greater focus on the cause of this variability, and emphasizing the importance of using the total morphological package for species diagnoses.

Another major finding of the study is that a grouping of H. naledi and specimens of Homo erectus "exceeds, in many instances, what we would expect if this grouping represented a single species."  Recall that we have zero idea how old this find is and, to the extent that this is possible, are trying to place this skull using only taxonomic analysis. Nonetheless, it gives us more information about this stage of hominin evolution and suggests that there was considerable variation of morphs running around during the transition from the australopithecines to early Homo. 

Scorecard on What YEC Sites Think of Homo naledi

Naturalis Historia posted a scorecard  on what the various opinions of Homo naledi are depending on which young earth creationist site you visit.  I have read and responded to the AiG post, which was flawed in its approach from the outset (it assumed that all australopithecines were only apes).

Hat Tip to Todd Wood at CORE.

Human Evolution = Apartheid?

About seven years ago, a Texas county official by the name of John Wiley Price made unwanted national news when he referred to the astronomical term “Black Hole” as racist. From the original story:

Later, Price told MyFOXdfw.com that he believed it and other terms were racist.

"So if it's 'angel food cake,' it's white. If it's 'devil's food cake,' it's black. If you're the 'black sheep of the family,' then you gotta be bad, you know. 'White sheep,' you're okay. You know?" Price said.

Price said people should watch their words when it comes to stereotypes.

"I think people should always be careful. You know, I'm okay if I'm 'bartering' with you. ... But if I try to 'Jew you down,' Oooooh. Is that racist? I thought it meant the same thing? No, maybe it doesn't."

Rather than confirm that the term “Black Hole” is racist, this story, instead, confirmed that science education had completely failed Mr. Price.That he could not distinguish between an astronomical term and a racial epithet was truly amazing.

A story today from South Africa is broadly similar in its absurdity.  As PhysOrg reports:

Some prominent South Africans have dismissed the discovery of a new human ancestor as a racist theory designed to cast Africans as "subhuman", an opinion that resonates in a country deeply bruised by apartheid.

"No one will dig old monkey bones to back up a theory that I was once a baboon. Sorry," said Zwelinzima Vavi, former general secretary of the powerful trade union group Cosatu, a faithful ally of the ruling African National Congress (ANC).

"I am no grandchild of any ape, monkey or baboon—finish en klaar (Afrikaans for "that's it")," he said on his Twitter account, which is followed by more than 300,000 people.

His comments were backed by the South African Council of Churches (SACC), which was historically involved in the fight against apartheid.

Cloaked in the fight against apartheid to give it legitimacy, this perspective is nothing more than anti-evolutionary creationism.  Incredulous, Richard Dawkins comments:

It "breathes new life into paranoia," said prominent British biologist Richard Dawkins on his Twitter account this week. "Whole point is we're all African apes."

He is correct. Importantly, just like Mr. Price, science education has failed Mr. Vavi. We are not descended from baboons. We never were. The large-bodied and small-bodied primates split sometime around the Oligocene Epoch, some 35 to 40 million years ago.  Baboons went one way and the apes went the other.

I am waiting for the Discovery Institute and Answers in Genesis to jump all over this.  The DI has attempted to link evolutionary theory with eugenics and racism before. As far as AiG is concerned, evolution is just plain evil. 

Or is Homo naledi Actually Homo erectus?

California Magazine, from the University of California at Berzerkeley, has an article written by Glen Martin, in which he details the skepticism about the taxonomic status of Homo naledi, specifically, that it does not represent a new species.  Martin writes:

The popular science press went bonkers last month with news that fossilized bones of a previously unknown hominid had been discovered in a cave system in South Africa. Dubbed Homo naledi by lead researcher and University of the Witwatersrand paleoanthropologist Lee Berger, these proto-humans appeared to have lived somewhere between 1 to 3 million years ago, used tools, walked upright, and may have buried their dead, a practice that has only been attributed to our own species, Homo sapiens, and Neanderthals.

So there was a lot of talk of a “missing link”—the biggest find in paleoanthropology since Lucy, the skeleton of a female Australopithecus, was excavated from a gully near Ethiopia’s Awash River in 1974. (Donald Johanson, the lead researcher in Lucy’s discovery team, founded the Institute of Human Origins, which later moved from Berkeley to Arizona State.)

As I mentioned in my post on the find, echoed by PZ Myers, at Pharyngula, this notion of a “missing link” is a straw man that has been created by the popular press and jumped on by organizations like the Discovery Institute and Answers in Genesis.  Martin continues:

Amid all the hoopla and confetti, however, a growing number of scientists are advising caution. They’re not denying the importance of the find; the fossils, they say, are invaluable. But they contend that the bones may not represent a new species. The evidence these skeptics point to suggests that the finds may actually be bones from
Homo erectus, the earliest known hominid to manifest the general proportions, stance and gait of modern humans. H. erectus had a long tenure on the planet, living from about 2 million to 70,000 years ago. The species was widely distributed (from Africa to East Asia and possibly southern Europe), used tools and fire, and may have constructed rafts to cross wide bodies of water.

Berger maintains that the skulls are too small, with too many primitive characteristics to be Homo erectus.  Once again, though, we come to the problem of how old the bones are.  Here, White is particularly critical:

One tibia, for example, was white on one end, a clear indication it had been snapped off in the recent past,” said White. “This (region’s) complex is extensive and like Swiss cheese, and it’s a favorite with spelunkers. You find beer cans next to fossils that are 3.5 million years old. So it’s important not to jump to conclusions.”

If the bones are late, as is possible, then the finds (or at least parts of them) might represent a Homo erectus population that has late primitive retentions. Even if there is more than one species present, there is no getting around the fact that the small, primitive cranium is where the Homo erectus traits are found, as well.

Berger is quoted as saying that this debate should play out in the published literature.  I suspect it will and that, eventually, we will figure out what sorts of primitive and derived traits the cache in the cave actually represents, even if we might never know exactly how old they are.

PZ Myers on Casey Luskin

PZ Myers, over at Pharyngula, has some harsh words for Casey Luskin's examination of Homo naledi.  In the post, he points out something that I have pointed out in several posts for BioLogos and in my rebuttal to Luskin's post on Homo naledi: a complete lack of understanding of systematics:

I’m not going to dissect every point in Luskin’s tediously long article in detail — really, he’s just echoing every question anyone has asked about H. naledi in the last few weeks, in an attempt to construct a litany of doubt — but I have to point out the numerous ways he misrepresents evolutionary biology to pretend that H. naledi is somehow a refutation of Darwin. As I’ve pointed out many times before, Luskin is a scientific illiterate who doesn’t actually understand anything remotely biological, from genetics to embryology to molecular biology to, now, paleontology. Actually, this isn’t the first time Luskin has tripped over himself in a rush to deny — he also didn’t like Tiktaalik. So this is just more of the same.

Luskin has a bad case of missinglinkitis. This is the idea that there is a linear series of steps in a progression leading from ape to human, and all we have to do is find each frame in the movie and we can replay everything in science class. He wants a “link”, a word he uses multiple times, and he wants “transitional fossils”, unaware that every individual is a transition between parent and progeny.

The key is to focus on the traits, something that Luskin and other Intelligent Design supporters fail to do. Myers further points out, as I did, that just about every fossil that we find is a mosaic of traits and when we follow the trait patterns, we can develop phylogenies.  This line of thinking has led to remarkable understanding of the evolution of Devonian tetrapods and the transition from theropod maniraptoran dinosaurs into birds. 

He also makes light of a point that Luskin makes about the venue that Berger and colleagues took when they wanted to publish the paper:

I have to mention two other lesser points from the paper. Luskin really knows nothing.

The technical paper, “Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa,” appeared in a lesser-known journal, eLife. It’s a great find due to the sheer number of bones that were found, but to my mind its publication in eLife is an immediate hint that this fossil isn’t an earthshattering “transitional form,” because if it were, we almost unquestionably would have seen the fossil published in Science or Nature.

No. Wrong. A lot of scientists resent the tyranny of the magical CV-enhancing powers of those two journals, and think they have an inflated and dangerously dominant reputation. eLife is an entirely credible new journal which, to all appearances, has a robust reputation for good, solid peer-review…and is also open source. There are a lot of scientists who are eager to see scientific information disseminated more widely without the limiting restrictions of traditional journal publishing, and Lee Berger, the lead investigator in this work, doesn’t need the résumé reinforcement that publishing in Nature or Science provides.

This is only half-correct. While it is quite true that many scientists like to publish in open-source publications like eLife and PLoS, this is not always the perspective of the managers and department heads, many of whom would much prefer that their researchers publish in high-profile journals, like Science and Nature.  I know this to be true through my work not just in publishing but in dealing with funders.  They like flashy papers.  This often (but not always) conflicts with the desires of the researchers, themselves.  Even though there are plenty of researchers who would like just to publish and get the information out there as fast as possible, I know of quite a few researchers who don't mind padding their resumes a bit with high-profile papers because they are angling for a position higher up on the academic food chain.  We would love to think otherwise, but it just isn't always true. 

Casey Luskin on Homo naledi

Casey Luskin has written a piece for Evolution, News and Views, in which he examines the hype surrounding the new Homo naledi find.  It would take more time than I have to tackle it point by point, but I will hit the high notes.  He writes:

It has long been recognized that we are missing fossils documenting the supposed transition from the apelike genus Australopithecus to the humanlike Homo. Despite what you may be hearing in the media, Homo naledi does not solve this problem.

That's okay. It wasn't meant to. It fills in a bit of a puzzle, that is all. We now have more information than we had about this transition, which appears to have been complex.  He continues:

Some have envisioned the hallowed intermediate link being a creature with an apelike body and a human-like head. For some time, Homo habilis was claimed to be such a candidate -- until cooler heads prevailed, as I noted earlier. Others have hoped we'd uncover something with a more Homo-like postcranial (below the head) skeleton but a more australopith-ape-like body. Indeed, almost exactly four years ago, in a post titled "Hominid Hype and the Election Cycle," I noted these precise arguments with regard to Australopithecus sediba.

Coincidently, we're right now in almost exactly the same place in the election cycle, and seeing almost identical claims about this new fossil discovery. Indeed, Homo naledi was discovered (and is being promoted) by the same researcher, Lee Berger, that unveiled (and promoted) sediba, although, as we'll see, naledi has a very different and unique set of traits from sediba.

One of the issues so far has been the dating of the remains.  Luskin, in quoting Carol Ward's concerns about lack of dating of the fossils, makes a legitimate objection in that we do not know how old the bones are.  That is a problem.  As I pointed out in my BioLogos post, we can date the cave floor, we can date the cave walls and we can date the cave ceiling but we have little to no idea when the bones were dropped in.  It is clear that the floor of this cave was not a living floor.  He writes:

The main claim about Homo naledi is that it is a small-brained hominin (when compared to humans) that has other features that are very humanlike -- especially its hands and feet. As the news headlines suggest, there has been an immense amount of hype about this species, consistent with the hype surrounding Australopithecus sediba, which again was discovered and promoted by the same researcher, Lee Berger. However, while there are some humanlike aspects of its body plan, my overall impression is that this is a highly unique species that doesn't fit well into previously established categories.

He is also correct about that.  It doesn't.  H. naledi has characteristics that link it with many different hominins and the combination of traits is unique.   This is not a problem it is, as Carol Ward commented, shows us that there was considerable hominin diversity at this time and, apparently at other times in the past.  The problem is that he uses selective passages and slanted wording to imply that the case for it having "human" traits is overblown.  For example:

  For example, Luskin writes:

The hands are claimed to be humanlike but they have key unique features and, unlike human hands, are tailored for climbing. ABC News reported: "Homo naledi had human-like hands and feet, but Tattersall said it was impressive that it also had climbing features, more similar to an ape." CNN reports: "Its hands are superficially humanlike, but the finger bones are locked into a curve -- a trait that suggests climbing and tool-using capabilities." And even Berger states: "It's pretty clear from those fingers that they're [for] climbing."

All of this is done to shift the emphasis away from the fact that, while the hominin did possess primitive traits, it also possessed derived ones. Let's see what Berger actually writes about the find:

The hand shares many derived features of modern humans and Neandertals in the thumb, wrist, and palm, but has relatively long and markedly curved fingers (Kivell et al., 2015). The thumb is long relative to the length of the other digits, and includes a robust metacarpal with well-developed intrinsic (M. opponens pollicis and M. first dorsal interosseous) muscle attachments.

Note the characteristics that Luskin leaves out.  With regard to our understanding of its taxonomic designation, Luskin writes:

Even Berger admits, "It doesn't look a lot like us." He also states: "There may be debate over the Homo designation" since "the species is quite different from anything else we have seen."

It wouldn't be surprising if later analyses change our understanding of the fossil.

He then puts in the following quote from an interview of Carol Ward in The Scientist:

Carol Ward, a professor of pathology and anatomical sciences at the University of Missouri who was not involved with the study said she was disappointed by the lack of empirical data presented in the paper. "There are only tiny composite pictures of the fossils, so you can't see them and there are no comparative data comparing it to anything else," said Ward. "There's nothing we can use to make our own judgments about the validity of what they are saying."

The problem is that he leaves out a rather significant statement about the find that precedes that. Here is the entire passage from the article (emphasis added):

“H. naledi possesses a combination of primitive and derived features not seen in the hand of any other hominin,” the authors wrote, but Carol Ward, a professor of pathology and anatomical sciences at the University of Missouri who was not involved with the study said she was disappointed by the lack of empirical data presented in the paper. “There are only tiny composite pictures of the fossils, so you can’t see them and there are no comparative data comparing it to anything else,” said Ward. “There’s nothing we can use to make our own judgments about the validity of what they are saying.”

Luskin has done two things here.  By removing the ellipses in from of the initial part of the quote, he suggests that this is a self-contained thought, which it clearly is not.  Further, by not quoting the initial statement of Ward's, he omits that she sees not just primitive but derived traits as well.  This is a pattern throughout his piece.

He phrases the rest of the piece in the form of four controversies.

The first is “How Old is Homo naledi?”  The irony here is that Luskin could very easily have focused on this topic and left it at that.  He has Berger over a barrel, here.  We don't know how old the bones are.  We have zero idea when they were dropped in. Gunter Brauer had a problem in the 1990s with an important skull in the transition to early modern humans, Eliye Springs, which washed out a bank where the spring entered Lake Turkana.  Great find, no idea what its age is.  As I mentioned in my blog post on Homo naledi, the South African cave sites present a serious problem for dating the hominins in which they are found.  Some success has been had but many finds are simply given wide chronological ranges.

Consequently, if Homo naledi is between 2 and 3 mya, it represents a find that is near where the transition is thought to occur, based on the presence of early Homo in East Africa, although the Ledi jaw may suggest an earlier transition.  On the other hand, if it is late, say 1 mya, then it simply represents a dead end that retained many primitive traits.

Here is what Luskin writes about this:

But some of naledi's advocates think they know what to make of the fossils, despite the compete current lack of an age for these fossils. How do they know? Evolutionary assumptions, which drive a desire among some that the bones should turn out to be somewhere between 2.5 and 3 million years old.

This is not entirely true and Luskin knows it, or ought to. There are perfectly valid reasons to suggest that this find is this old, even if we do not, in fact, know its age. For one thing, we know that we have hominins in East Africa that have derived traits toward modern humans between 2.3 and 1.8 million years ago.  Consequently, we know that the transition to this form(s) took place somewhere between 2.5 and 3.0 million years ago.  Further, this tracks with the discovery of the Ledi jaw, which has a mix of australopithecine and early Homo traits and is dated to 2.8 mya.  Therefore, do we know how old the Homo naledi fossils are?  No, we don't.  Are the estimated dates just being driven by evolutionary assumptions?  Clearly not.

Controversy Number 2: “Is Homo naledi a single species?”  Luskin writes:

The question of whether the bones currently assigned to Homo naledi represent a single species may seem like an academic one but it actually could bear directly upon whether it's something like a transitional form, or nothing of the kind. Jeffrey Schwartz, an anthropologist at the University of Pittsburgh, thinks the bones represent multiple species because of the two different types of skulls found in the cave.

Where Luskin is going with this is that, if there are, in fact, two different species in the cave, then some of them might just be modern human.  He continues:

The fact that Berger appeals to sexual dimorphism (different morphologies between males and females of a single species) to explain the different skulls is revealing. It shows that there is indeed a challenge to his "single species" claim. However, if there are multiple species, then you don't necessarily know that humanlike hands and feet didn't come from something more like us, whereas the small heads came from another species more like an australopith. We just don't know.

Here, he glosses over something very important:  even the human-like skeletal material has characteristics that are not modern for example:

• The small heads have both angular and occipital tori, characteristics only found on Homo erectus.  No australopithecine has these and no modern human does, either.
• The faces, while being small, lack australopithecine traits such as canine jugae and anterior pillars.  Further, there is limited post-orbital constriction, a more modern characteristic.
• Even the “human-like” hands and feet have characteristics that are primitive. For example, Berger writes: 

  The talar head and neck exhibit strong, humanlike torsion; the horizontal angle is higher than in most humans, similar to that found in australopiths. The calcaneus is only moderately robust, but possesses the plantar declination of the retrotrochlear eminence and plantarly positioned lateral plantar process found in both modern humans and Au. afarensis...The phalanges are moderately curved, slightly more so than in H. sapiens. The only primitive anatomies found in the foot of H. naledi are the talar head and neck declination and sustentaculum tali angles, suggestive of a lower arched foot with a more plantarly positioned and horizontally inclined medial column than typically found in modern humans...Overall, carpal shapes and articular configurations are very similar to those of modern humans and Neandertals, and unlike those of great apes and other extinct hominins. However, the H. naledi wrist lacks a third metacarpal styloid process, has a more radioulnarly oriented capitate-Mc2 joint, and has a relatively small trapezium-Mc1 joint compared to humans and Neandertals. Moreover, the phalanges are long (relative to the palm) and more curved than most australopiths.

Therefore, appeals to there being modern humans in the cave along with australopithecines are not warranted. Maybe there was more than one species in the cave and one of them was an australopithecine. What remained, however, was not modern human.  There are no modern humans walking around with angular and occipital tori.

But say there is more than one species down there, and these different species represent different times in the history of hominin evolution.  Would this be a bad thing? What it would mean is that there is a good deal of variability in the human fossil record, something we already suspected anyway.  We know that expanded diversity existed as far back as Ardipithecus.  Why would it not be present at other times?

Controversy No. 3: Did Homo naledi Bury Its Dead?  Here is Luskin:

A major claim being promoted in the media holds that Homo naledi ritualistically buried its dead, a testimony to its supposedly human-like intellect.

and

Even if this story is true, it's not the case that this species buried its dead in any manner like humans bury their dead. The bones weren't buried in the ground. Rather, it seems like the bodies were just tossed into the back crevice of a cave and left there to rot...

Luskin is correct that the media attention to this is overblown and sensationalistic. Luskin goes on, then to quote many different researchers who are skeptical about this claim (skepticism that I think is warranted, by the way) But let's see what Berger et al. say about it. First, the word “burial” never appears once in the original paper by Berger et al. That information comes from the supplementary paper by Dirks et al., who write this:

The Dinaledi collection displays taphonomic characteristics indicative of a depositional history that involved several stages of burial with surface modifications and breakage patterns consistent with repeated reworking of at least part of the assemblage within the confines of the Dinaledi Chamber, involving both biotic and abiotic agents (Supplementary file 2). The distribution of bone material and skeletal part representation indicative of limited winnowing (Table 1) indicate that the fossils of H. naledi must have found their way into the chamber via a difficult route that precluded any other large vertebrates from finding a way in. The distribution of the fossils within reworked material derived from Unit 2, as well-articulated remains in Unit 3 suggests that H. naledi fossils entered the chamber over an extended period of time; that is, not all remains were deposited at once.

So that is what we know, and that is all we know.  First, I was wrong in my post on BioLogos, this is not a standard karst cave with a top opening of any kind.  Consequently, there is no way for the bones to have gotten there unless they were placed there.  There is one possible explanation that is not mentioned by Dirks that is not in the account by Luskin:

Flowstone formation continues today (Flowstone 3), changing the morphology of cave passages. This makes it possible that a more direct access-way or easier passage may have existed when hominins entered. A different entrance into the chamber may also explain the presence of rodent bone concentrations in Facies 1b. However, sedimentation patterns indicate that the accumulation of Unit 2 with fossils occurred below the current entry point into the chamber, and alternate routes did not involve vertical access shafts that connected directly to surface in either the Dinaledi Chamber or nearby Dragon's Back Chamber.

This doesn't address the reliability of the burial hypothesis but it does suggest that it might have been much easier for the bones to get where they were.  I suspect that Jungers is correct in his hypothesis about whether or not they were intentionally buried.

Controversy No. 4: Does "Homo" naledi Belong in Homo? Luskin writes:

Ian Tattersall told ABC News: "We're [probably] looking at a cousin rather than an ancestor, but who knows."

"Who knows..." That is exactly right. Even Berger stated: "We need to be very cautious about proclaiming everything we find as the direct ancestors of humans, it's clear there are a lot of experiments going on out there."

Much is left out of this series of statements. Let's go back to the ABC article from which it is quoted:

Researchers said the newly discovered species most resembles other hominids such as Homo erectus, Homo habilis and Homo rudolfensis.

Ian Tattersall, curator emeritus at the American Museum of Natural History in New York, said the find was incredibly important and could shed important light on Homo sapiens, modern humans, as a species and the many other early hominoids.

“It’s really very exciting,” Tattersall told ABC News. “What this is doing is definitely increasing the perception that we have -- that evolution of hominids was one of vigorous experimentation of evolution.”

Why would the find shed any light on Homo if it did not have any characteristics of Homo? As numerous researchers have commented, it absolutely does.  Many of the characteristics that align it with Homo erectus have been pointed out, as well as other deviations from australopithecines.

Much of what Luskin is trying to accomplish in this section is focused on the fact that, while the Dinaledi finds have characteristics that align them with Homo, they also have some that align them with australopithecines and maybe we are over-interpreting the early Homo ones.  He then vaguely supports his case by using a series of quotes from researchers who are skeptical that we know exactly what H. naledi actually is.  For example, he writes this:

Schwartz himself wrote a scathing op-ed in Newsweek, "Why the Homo Naledi Discovery May Not Be Quite What it Seems." He argued that "Homo naledi" may in fact represent multiple species, and probably doesn't belong in Homo:

Interestingly, he then quotes Schwartz, who points out only the australopithecine portions of the anatomy, to the exclusion of any of the modern traits that it has.  While it is quite true that there are differing opinions about what these finds represent, it is equally true that there are Homo traits present.  Consequently, to simply lump them in with australopithecines is inaccurate.  It may be years before we have enough information to make a sound judgment about exactly where this fits in the pantheon of human evolution, but for now, we can safely say that, whether or not there are one species present or two, a hominin with some of the traits of early Homo was present at this cave.

But even if

it turns out that H. naledi is, in fact, Au. naledi, after much reflection.  Then it just means that australopithecine diversity is greater than we thought it was and that there were many different morphs that exhibited a wide range of traits, some of which were derived in the direction of Homo.  That we don't know exactly which form gave rise to an early Homo form is not a deal-breaker.  Remember, systematics does not reveal ancestor-descendant relationships, but, instead, sister taxa.  Au. sediba and H. naledi are two different forms that express a mosaic of traits, some of which are advanced and some which are not.  They are both considerably more advanced than the australopithecines that preceded them.

Luskin is focused on the fact that H. naledi is probably not the missing link between the australopithecines and early Homo that everybody was hoping for.  That is beside the point.  The point is we now know quite a bit more about this stage of human evolution.  Even if the bones turn out to be younger than we thought, it still gives us information about human evolutionary development that we did not already have.  That's okay.

Debating Homo naledi on Premier Christian Radio

I took part in a debate on Premier Christian Radio last Thursday with Fuz Rana, of Reasons to Believe, on the new Homo naledi find and the respective cases for evolution and intelligent design.  It was quite fun and very cordial and respectful.  The host, Justin Brierley did a very good job of moderating and asking the right questions.  Let me know what you think.  Fuz spent some time talking about the book Who Was Adam? he co-wrote with Hugh Ross which, I am embarrassed to say, I have not read yet.  I need to do that post-haste. 

BioLogos Post on Homo naledi is Up

My question-and-answer post with Brad Kramer is up at BioLogos.  Comments welcome there and here.

Darrel Falk's Post on Homo naledi

Darrel Falk has a short post on Homo naledi, in which he discusses the nature of the science and misconceptions that we have had with regard to human evolution.  He writes:

Interestingly, besides all the PR associated with the discovery, it is documented by likely the finest Nova/National Geographic production I have ever seen on human evolution, which is available to view online here. I've watched the first hour of the two hour special which will appear next Wednesday evening (Sept 16) on PBS. I love it because it shows in absolutely exciting detail how the science is done. It also shows how wrong earlier paleontologists were regarding the nature of our early ancestors—they weren't 'killers' as depicted in early film and scientific literature. They were plant eaters with likely the occasional meat meal. The natural forces associated with the evolution of the human body were NOT selection for the fittest killers. Indeed, although not specifically discussed in the film (I've not quite finished it), cooperation was likely a much more important shaper of the distinctively human mind than competition.

As was outlined in the Nova special, it was the work of Bob Brain, who discovered that marks in the skull that had been attributed to interpersonal violence on the part of australopithecines, were, in fact, created by large cat predators.

My BioLogos post on Homo naledi will be out shortly.

Nova Special: Dawn of Humanity

Nova will be airing a special tonight (9/16) on the Dawn of Humanity, focusing on the new Homo naledi finds from South Africa.  The video is also streaming on the PBS site here.  I am currently writing up a piece for BioLogos which should appear soon.  So, too, is Elizabeth Mitchell of AiG, from what I understand. 

Early Homo in South Africa

The New York Times is reporting on a new find out of South Africa, by Lee Berger and his team, that indicates the presence of early Homo there.  John Noble Wilford writes:

The new hominin species was announced on Thursday by an international team of more than 60 scientists led by Lee R. Berger, an American paleoanthropologist who is a professor of human evolution studies at the University of the Witwatersrand in Johannesburg. The species name, H. naledi, refers to the cave where the bones lay undisturbed for so long; “naledi” means “star” in the local Sesotho language.

In two papers published this week in the open-access journal eLife, the researchers said that the more than 1,550 fossil elements documenting the discovery constituted the largest sample for any hominin species in a single African site, and one of the largest anywhere in the world. Further, the scientists said, that sample is probably a small fraction of the fossils yet to be recovered from the chamber. So far the team has recovered parts of at least 15 individuals.

“With almost every bone in the body represented multiple times, Homo naledi is already practically the best-known fossil member of our lineage,” Dr. Berger said.

Here is the link to the first paper, Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa, and here is the link to the taphonomic paper, Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa. Here is the picture from the main paper, as well as the abstract:

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

What does this mean?  Well, the principle problem is that we still have no date for these remains, so it is difficult to place them chronologically.  Berger is standing by his contention that early Homo arose from something like Au sediba, despite evidence to the contrary recently uncovered in Northeast Africa.  If the date is late, somewhere on the order of one million years, then a migration model might explain the appearance of such an advanced hominin in this area.  If it turns out to be much older, then other models might have to be entertained.  More thoughts on this find later.