Archive for the ‘homo naledi’ Category
Homo naledi – an enigma shrouded in mystery
remains of at least 18 individuals found
Jacinta: So, having watched the much-discussed Netflix film, Cave of bones, describing and indeed taking us into the depths of the Rising Star underground cave system, frequented by the very enigmatic and so controversial Homo naledi species of hominin, and knowing that there is ‘blowback’ (presumably an Americanism) about the claims made re burial practices and lithic tool-making dating back a possible 300,000 years by this small-brained creature, remains of which have never been found above-ground, as far as I’m aware, we’ve decided to do one of our shallow dives into the claims and counter-claims…
Canto: So the researchers featured in the film include Lee Berger and John Hawkes, both names to reckon with in paleoanthropology, and they present a claim that they found evidence of burial practice in the Dinaledi Chamber at the barely accessible base of the complex Rising Star system. The film, I have to say, is edge-of-the-seat absorbing, though its intense focus on this one possible child-burial site, and the possible stone tool buried with the child, means you’d be forgiven for not having a clue about the broader perspective. That’s to say, that –
the Dinaledi Chamber of the Rising Star Cave has yielded 1550 identifiable fossil elements – representing the largest single collection of fossil hominin material found on the African continent to date.
Jacinta: Yes, that’s from University College London, but are they all from H naledi, I wonder? Apparently so, according to the Australian Museum:
The remains of at least 15 individuals were found in the Rising Star cave system in South Africa and announced as a new human species in 2015. The remains are the largest assemblage of a single hominin species yet discovered in Africa. Homo naledi combines primitive with modern features and is not a direct ancestor of modern humans.
They’ve been dated to between 335,000 and 236,000 years, but that presumably only indicates the dates in which the cave system was used. In another underground cave nearby (Lesedi cave), remains of at least two adults and a juvenile were found – also H naledi. Attempts to extract DNA have so far failed. And the fact that no fossils of these species have been found elsewhere isn’t perhaps surprising, caves being the place for such finds. But there’s hope for the future, according to the museum:
As only small parts of both caves were excavated, many more bones remain for future expeditions to recover.
Canto: So, in the film, Berger, Hawkes and their team reflect at large on ancient burial practices and religion and how far back they can be traced in hominin ancestry, but a very recent article in Nature throws something of a wet blanket over all this conjecture.
Jacinta: Yes, the film, which I have to say is very engaging, and even quite emotional for me, for some reason, came out at about the same time as peer reviews of an article by the researchers in an apparently controversial journal, eLife. These reviews were all pretty negative, as reported in Nature. Here’s one response:
“I want to understand how the H. naledi fossils got there. They are very important fossils, and critical to understanding human evolution,” says Jamie Hodgkins, a palaeoarchaeologist at the University of Colorado Denver, who was one of the study’s four reviewers for eLife. However, “there just wasn’t any science in the paper ultimately”.
And being still under the sway of the film, I feel a bit defensive for Berger and co. I know that Berger has a bit of a rep for being a rebel in the field, but I was interested in the possibilities raised by the film, which are somewhat similar to the conjectures being raised by Rebecca Wragg Sykes in her Neanderthal book, Kindred, especially in the chapter entitled ‘Many Ways to Die’, which explores possibilities re Neanderthal burial practices, as well as other ways of treating the dead, such as a kind of devotional cannibalism…
Canto: Mmmm, tasty.
Jacinta: Sykes cites many cases of Neanderthal cannibalism, and speculates as to the purpose. She considers that it was rarely out of hunger, and makes this interesting observation re our favourite rellies:
Bonobos once again provide an intriguing counterpoint. There are no recorded infanticides, yet several cases of mother-infant cannibalism exist, which also featured meat-sharing. In one situation, following a baby’s natural death the group spent an entire morning eating much of the body, before the mother carried away the remnants on her back.
Kindred, p 309
Canto Yes, well, I don’t think we’ve reached that stage of advancement.
Jacinta: Anyway, Sykes doesn’t go beyond speculation as to Neanderthal burial, but Berger et al really push their case hard, in their paper for eLife, titled ‘Evidence for deliberate burial of the dead by Homo naledi’. And via a very long and painstaking video analysis of the paper and its peer reviews by the intellectually and otherwise alluring ‘Gutsick Gibbon’ (aka Erica, I believe), which I’m only halfway through watching, I’ve become convinced that the evidence presented in the film isn’t convincing. As to the paper itself, I’m only getting snatches of it through the commentary. I was prepared to believe, before watching this video, that there was a bit of professional jealousy going on, due to Berger’s paleontological superstardom (given that the H naledi discovery, which Berger more or less owns, really is pretty mind-blowing), but the reviewers, being expert in such essential fields as archaeothanatology, sedimentology, micromorphology, palaeo-osteology and commonsensology, really focus on the failings, the lack of support for bold assertions, in very professional and indeed enlightening ways.
Canto: Yes, it actually made me want to read more papers on some of these subjects, and to be involved – to be young would be very heaven… The major theme of the response, to me, was ‘more research needed’, and especially from more specialised experts. And the film made me aware of how difficult – and dangerous – in situ research is for this site.
Jacinta: Yes it seems to be only the beginning with Homo naledi. But I think the criticism was more pointed, along the lines of ‘extraordinary claims require extraordinary evidence’. The signs of possible Neanderthal burials, which Sykes is quite carefully speculative about, at various sites (Sima de las Palomas, La Ferrassie, Shanidar), are all dated to less than 50,000 years ago, while the H naledi ‘burials’ – or is there only one? – are more than 5 times further back. Unlikely – though the brain size thing is a bit of a red herring to me. Think H floresiensis – too primitive to survive, or just island dwarfism?
Canto: Who knows, but it’s a good point. Island dwarfism occurred in the past, e.g. with elephants, but were they made less intelligent thereby? Surely not. And corvids have walnut-brains, with as many neurons as some monkey species. Size isn’t everything, check this out.
Jacinta: Please put it away. And nobody is saying that H naledi were dwarf hominins. Anyway, the major takeaway, comme on dit, is that this is just the beginning for Homo naledi. They need to be more disciplined about their claims, and maybe Berger’s enthusiasm, as evidenced in the Netflix film, is getting the better of his professional judgement. There will be further exploration of this challenging environment, and more and more incisive technology will be developed, as alway seems to happen.
Canto: So, in Gutsick Gibbon’s video we get to Berger at al’s response to the criticisms, with their main argument (about their contention that this was a deliberate burial) seeming to be that ‘there may be more types of burial on earth than are ever comprehended in your philosophy’, if I may murder Shakespeare, and that it might even be expected that a species far removed from H sapiens would have such quite different burial processes. And yet they’re claiming recognition of these more or less unrecognisable processes.
Jacinta: Yeah, it’s a bit like saying ‘there are aliens among us, but people are too dumb to see them – but we can see them’. Or maybe not. As Ms Gibbon points out, why didn’t the team stick with the original null hypothesis, that this was a sort of dumping ground, albeit a sorta respectful one, for their dead? That null hypothesis, by the way, might sit somewhere in the grey zone between, or sort of combining, the cultural and the natural.
Canto: Yes, Gutsick Gibbon weighs in on the question of whether we should look at sites of early hominins such as Australopithecus with more of a cultural null hypothesis than a natural one. She thinks ‘natural’, but I’d be more agnostic, partly because I’m too ignorant of palaeontology to take a strong stand, but also, as with my interest in bonobos, I’m prepared to take the widest possible view of culture.
Jacinta: Yes, in that disturbing chapter of Kindred which presents quite extensive evidence of Neanderthal cannibalism, and explores the reasons for such behaviour, Sykes suggests something in that cultural/natural grey zone. Again, she compares observed behaviour of bonobos and chimps:
For both bonobos and chimpanzees, the bodies of the dead evoke many emotions. Even if the process often begins with trauma and confusion, typically corpses shift to a liminal status; not alive, but equally not a lump of meat. They’re more intensively manipulated than hunted animals, and carried for longer. In some – if not all – cases, the eaters must know what and who they’re consuming. Cannibalism is very probably a powerful means by which individuals and groups process the impact not only of killings carried out on emotional impulses, but other deaths too. In other words, it’s about grieving.
Kindred, pp 309-10
Canto: Yes, I’m not sure what to think of that thesis, I’m not entirely convinced, but my mind is open and my brain’s not falling out. We’re only at the beginning, with H naledi and so much more…
References
https://www.netflix.com/au/title/81473682
Kindred: Neanderthal life, love, death and art, by Rebecca Wragg Sykes, 2020.
https://australian.museum/learn/science/human-evolution/homo-naledi/
Human origins far from being resolved – it just gets more fascinating (part 1)
yeah – a few ‘awkward’ species missing from this group
Canto: So we’d all like to solve the riddle – or many riddles, of human ancestry, but the problems are manifold, it seems.
Jacinta: Yes, we’re not just talking about Homo sapiens, or H sapiens sapiens as some would put it, but the whole Homo genus, including neanderthalenis, denisova, floresiensis, naledi, heidelbergensis, rudolfensis, erectus and habilis, and I’m not sure if I’ve got them all.
Canto: Yes and there are lumpers and splitters, but I’m talking even further back, to Paranthropus and the Australopithecines. I watched a DW doco recently that piqued my interest, making me wonder at what date, round-about, did the Homo genus emerge, and what genus did it emerge from?
Jacinta: Well this is a problem for all species and genera really. Think of our favourite apes, the bonobos. In the book Who we are and how we got here, which is all about the new science of genomics and how it’s transforming our understanding of human populations , David Reich wrote of –
a new method to estimate the suddenness of separation of the ancestors of two present-day species from genetic data… When they applied the method to study the separation time of common chimpanzees and their cousins, bonobos, they found evidence that the separation was very sudden, consistent with the hypothesis that the species were separated by a huge river (the Congo) that formed rather suddenly one to two million years ago
D Reich, Who we are and how we got here, p46
Which is all very fascinating, but one to two million years is rather a long time frame.
Canto: Yes, in the DW doco the time frames were also rather flexible – which I suppose needs must. Australopithecines were described as emerging perhaps 3 million years ago and disappearing 2 million years ago, with the Paranthropus genus preceding them by about a million years – or was it the other way around?
Jacinta: And other types are mentioned – often from the most meagre remains. Sahelanthropus, Orrorin, Ardipithecus, and Danuvius guggenmosi, beloved of Madelaine Böhme among others.
Canto: Well D guggenmosi was an interesting but isolated find, dating to around 11.6 million years ago, and of course the remains are fragmentary so there are arguments about its bipedalism and other features. It was a tiny ape, quite a bit smaller than bonobos, the smallest of the extant great apes. Böhme is arguing, I believe, that these discoveries (three specimens were discovered) could push the chimp-human last common ancestor (CHLCA) back a few million years. The CHLCA date is usually given as between 6 and 7 million years ago, but Wikipedia is, currently at least, being more open to a wider range:
The chimpanzee–human last common ancestor (CHLCA) is the last common ancestor shared by the extant Homo (human) and Pan (chimpanzee and bonobo) genera of Hominini. Due to complex hybrid speciation, it is not currently possible to give a precise estimate on the age of this ancestral population. While “original divergence” between populations may have occurred as early as 13 million years ago (Miocene), hybridization may have been ongoing until as recently as 4 million years ago (Pliocene).
Chimpanzee–human last common ancestor, Wikipedia Jan 21 2023
Jacinta: Interesting, and it suggests a lot of work still to be done, and that’s just in relation to the Homo genus. I’d certainly be interested in pursuing the evidence and the debate in future posts, but for now I’m wondering about the immediate ancestors of our species.
Canto: Well, the book Who we are and how we got here tries to sort all that out through the study of population genetics and genomics, though much of it, so far, deals with migratory populations over the last tens of thousands of years…
Jacinta: Homo heidelbergensis has struck many palaeoanthropologists as the likely common ancestor of both H sapiens and H neanderthalensis. The Smithsonian dates the species to about 700,000 to 200,000 years ago, but there’s also this from their website:
This species may reach back to 1.3 million years ago, and include early humans from Spain (‘Homo antecessor’ fossils and archeological evidence from 800,000 to 1.3 million years old), England (archeological remains back to about 1 million years old), and Italy (from the site of Ceprano, possibly as old as 1 million years)
Canto: So yes, again, lumpers and splitters, and we’re no experts. From the term Homo antecessor I’d conjecture that they’ve been hailed as direct antecedents…. but other specimens, named H cepranensis, and H rhodesiensis, as well as H heidelbergensis, are in the mix, and the remains are often hard to identify and date, with DNA and the proteins made from them being tricky to isolate from warmer climes…
Jacinta: The Australian Museum gives us this interesting info about H heidelbergensis versus H antecessor, in describing the largest find of specimens:
- The remains of at least 6 individuals found at the site of Gran Dolina, Atapuerca, in Spain. They lived about 800,000 to 1 million years ago in Europe and are the oldest human remains found in that continent. Although many experts consider these remains to be part of an early and variable Homo heidelbergensis population, the discoverers believe the fossils are different enough to be given a new species name Homo antecessor.
Canto: I’m wondering about that Morocco specimen that has recently, no doubt controversially, been reclassified as H sapiens, though it dates from 320,000 to 300,000 years ago, pushing the age of our species back by a hundred thousand years or so.
Jacinta: Yes you’re talking about the finds at the Jebel Irhoud site, and it’s complicated, because most researchers don’t identify that region as the birthplace of H sapiens. They mostly agree that the species was ‘born’ in southern and Eastern Africa. The Smithsonian seems to me a bit confusing and unconvincing on this point:
The remains of five individuals at Jebel Irhoud exhibit traits of a face that looks compellingly modern, mixed with other traits like an elongated brain case reminiscent of more archaic humans. The remains’ presence in the northwestern corner of Africa isn’t evidence of our origin point, but rather of how widely spread humans were across Africa even at this early date.
They’re saying that the oldest human remains found are in north-west Africa, but humans probably originated in south-east Africa, though we haven’t got specimens from there that are older than 260,000 years, at most. Hmmm.
Canto: The paucity of the fossil record is probably to blame. But then – Homo naledi. I’ve just watched John Hawks giving a talk on naledi in 2017 – Hawks is a hero of mine, I used to follow his website regularly – and he talked of more and more discoveries in that diabolical underground cave system called – maybe ironically? – Rising Star, in South Africa. They now have more fossil remains of naledi than of any other ancient Homo apart from neanderthalensis. And they’ve managed to narrow the dating from about 320,000 to 240,000 years ago, from memory. So they may well have lived alongside the earliest H sapiens.
Jacinta: Complexifying the picture in ways some find fascinating, others frustrating. And they were much smaller and smaller-brained, right? Like floresiensis, another mystery. So there will be questions about how ‘advanced’ they were. Is there evidence of tool use? Of fire? And remember, it’s not brain size that matters so much but brain organisation. Think of corvids – tool users, problem solvers, complex family systems, brains the size of a walnut but packed with as many neurons as some monkey species.
Canto: Yes, I agree, we can’t make too many assumptions based on size. Bonobos females are smaller than the males but much smarter, right? But one major difficulty about the naledi lifestyle is that we know nothing about it. It seems these remains were placed, or dropped, in the cave after death. And as far as I know, we have no trace of naledi above-ground, which is kind of bizarre.
Jacinta: Okay, so I’m watching the ever-reliable North 02 vid on naledi. They first thought these remains were probably well over a million years old, due to various features, especially skull size, though there were plenty of anomalies, but they were eventually able to date some of the teeth, using electron spin resonance and uranium-thorium dating, and yes, your dating is about right. As to skull or brain size, smaller than habilis and quite a bit smaller than erectus, but actually larger than floresiensis, which clearly tells us, doesn’t it, that there hasn’t necessarily been this enlargement of brain size over time for all members of the Homo genus.
Canto: Yes, interesting – floresiensis, do we know anything of their lifestyle, tools, decorations…?
Jacinta: The most recent dating of floresiensis has them living until about 50,000 years ago at the latest. So much more recent than naledi. The cave where they were found yielded over 10,000 stone artefacts similar to those associated with the much larger-brained H erectus, from whom they may have learned a few things. With a brain quite a bit smaller than that of H naledi. Surely a cautionary tale.
Canto: Right – and they’re not even looking at brains, they’re looking at skulls, and making possibly unwarranted assumptions.
Jacinta: Okay so there’s a lot more to say on this topic – about Homo naledi alone, never mind the many other species or pseudo-species, so we’ll have to turn this into an ongoing series. I’ve been reading and listening to a lot of very smart people, which has made me feel quite dumb and shallow on the topic – no Dunning-Kruger effect for me at least.
Canto: Well, even as dilettantes we’ve come up with some reasonable skeptical queries – about brain size, and more on that next time, about tool use or the lack of evidence for it, and the lack of evidence of anything re H naledi outside of Rising Star. So, next time…
References
How did humans come to be? DW documentary
D Reich, Who we are and how we got here, 2018
M Böhme et al, Ancient bones, 2020
https://en.wikipedia.org/wiki/Chimpanzee–human_last_common_ancestor
https://humanorigins.si.edu/evidence/human-fossils/species/homo-heidelbergensis
https://australian.museum/learn/science/human-evolution/homo-antecessor/