Archive for the ‘Homo sapiens’ 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/
humans and neanderthals and chimps and bonobos
We now know for sure that humans and neanderthals interbred. How much, we don’t know, nor do we know the nature of the interbreeding. The spectrum presumably goes from love and flowers to warfare slaughter and rape, and I recently heard one pundit arguing for the latter option, and I tend to agree, especially given what information ancient DNA is providing about human populations over the last 50,000 years or so – that’s to say, it appears that it was much less a case of cultures and practises spreading from one place to another than populations replacing earlier populations. And it may well be that we’ll get a more gory-detail picture of human-neanderthal intimacies in the foreseeable.
We’ve also learned that chimps and bonobos bonked after their separation due to the creation of the Congo River between one and two million years ago. I wish I’d been there to see it. My guess is that would’ve been far less traumatic, though perhaps not too lovey-dovey either.
So if we accept that violence was involved – who were the perps and who the victims? My feeling is that humans were the rapists, for the simple reason that we’re still here. Neanderthals disappeared some 40,000 years ago, though a remnant population appears to have survived in the Iberian Peninsula for another few thousand years. With chimps and bonobos it was probably more fifty-fifty, though I’m prepared to accept that nothing is ever that simple.
The fact that many of us – I don’t know about me – have some neanderthal DNA is probably a mixed blessing (some genes for absorbing sunlight may have predisposed us to skin cancer, others may have affected our ability to process carbs), but it hasn’t prevented us from quadrupling our population in the last century. And since we’ve produced the first whole-genome sequence of the neanderthal genome, they’ll soon be back with us, so no worries. Unfortunately, their memories of what we did to them will have been wiped, but we’re working on it.
Seriously, humans most likely were one of many contributors to neanderthal extinction. The two species shared similar European territories for the last few millennia before their disappearance, with human numbers apparently growing as neanderthals dwindled. Maybe they were out-competed in hunting big game, and small, as their diets would’ve been more or less identical to ours. Studies of neanderthal teeth from different environments (north-west and south-west Europe) indicate that they were opportunistic dieters, eating more meat in some regions, less in others, not all-out carnivores as previously thought, so this brings them even closer in line with humans, and in competition with them when habitats overlapped. And if anything, ancient DNA is telling us that our human ancestry was even more violent than previously thought – and we’ve long known how bad it was.
We don’t have any direct evidence that modern humans killed neanderthals, and we may never have such evidence. Professor Chris Stringer of London’s Natural History Museum argues that, as we now know that both species inhabited Western Europe for about 10,000 years before neanderthals died out, there was more likely a kind of awkward balance between the two species for much of that time. So, maybe killing but not outright extermination. Of course the same can be said for the large mammals that humans hunted. There was never any intention to exterminate them, but the pressure they were put under did for them in the end.
With chimps and bonobos, that seems to me even more of a mystery. What does a chimp look like to a bonobo, and vice versa? Most of us wouldn’t be able to tell one from the other, but that’s because we’re humans. In the past, Europeans used to say that all Chinese looked the same. Back in Darwin’s day and before, the people of Africa, Australia and Indonesia were collectively termed ‘savages’ by ‘white’ people. It’s taken a while for us dumb humans to become more discriminating. So it’s hardly surprising that bonobos weren’t recognised as a separate species from chimps until well into the twentieth century. Speciation itself is a rather more complicated and questionable affair than it was thought to be in the time of Linnaeus – and it wasn’t particularly simple then. Here’s an interesting quote from a Science article on chimp-bonobo interbreeding:
These findings come on the heels of other genome analyses—such as between coyotes, dogs, and wolves—showing such gene flow between species. “The more we look at genomes, the more it seems to be found,” [Professor Jim Mallet] says. “It’s going to be pretty common,” he predicts.
An article in earth.com, a popular science site, linked below, provides a summary of the physical and social differences between bonobos and chimps, though I can’t vouch for its accuracy – for example it claims that bonobo males and females are ‘much closer in size’ than chimp males and females. I’d always thought that the sexual dimorphism difference was slight, now I’m not so sure. Another interesting difference, that I’d not noticed before in my reading, is that bonobos have dark faces from birth, whereas chimps’ faces are lighter, and darken with age. I can well believe though that there are individual differences, in this as in robustness and gracility, bonobos being in general more gracile. Of course, chimp males are more dominant, so I can well imagine chimp-bonobo interbreeding to be a violent affair. And with bonobo females tending to stick together it would’ve been difficult to pick off an isolated female. Perhaps we should build a few Pan-friendly bridges across the Congo River and see what happens….
References
https://www.americanscientist.org/blog/science-culture/neanderthals-in-prime-time
https://www.science.org/content/article/chimps-and-bonobos-had-flings-and-swapped-genes-past
https://www.earth.com/earthpedia-articles/chimpanzees-vs-bonobos-whats-the-difference/
Did bonobos do it with chimps? Well, duh
bonobos or chimps? Or both? Or neither? What’s in a name…?
Canto: So we’ve been learning than we did it with Neanderthals, and that Neanderthals did it with Denisovans, and I remember hearing an anthropologist or palaeontologist saying that it’s likely that our split with our last common ancestor with chimps and bonobos – they call it the CHLCA (chimp-human last common ancestor, eliminating bonobos altogether, sigh) – wasn’t necessarily a clean break, which surely makes sense.
Jacinta: Well, yes, as we’ve read, the split was caused by the relatively sudden creation of the Congo River, but the word ‘relatively’, is, well, relative. So this raises the question of speciation in general. Think of those Galapagos finches that so intrigued Darwin. All about differently-shaped beaks, but it didn’t happen overnight.
Canto: Right, so here’s what a website with the rather all-encompassing title “Science” says about our topic:
Tens of thousands of years ago, modern humans slept around with Neandertals and swapped some genes. Now, it turns out one of our closest living relatives, chimpanzees, also dallied with another species. New research reveals that chimps mixed it up with bonobos at least twice during the 2 million years since these great apes started evolving their own identities. Although it’s not yet clear whether the acquired genes were ultimately beneficial or harmful, the finding strengthens the idea that such cross-species mating played an important role in the evolution of the great apes.
Jacinta: Interestingly this Congo River separation which led to a completely different species was repeated by other separations which led to four sub-species of chimps. Which leads me to wonder – what’s the difference between a new species and a sub-species? Why are bonobos ‘deserving’ of being called a different species?
Canto: Well the Science article has some fascinating further information. This was the work of Christina Hvilsom and colleagues, described as ‘conservation geneticists’. They were using any genetic differences they could find to work out where particular chimps were being caught or hunted. But, since the interbreeding of humans and Neanderthals, proven by DNA, had hit the headlines, Hvilsom wondered about the DNA of chimps. So, using the same methods that uncovered Neanderthal in humans –
she and her colleagues determined that 1% of the central chimpanzee’s genome is bonobo DNA. The genetic analysis indicates that this inbreeding happened during two time periods: 1.5 million years ago bonobo ancestors mixed with the ancestor of the eastern and central chimps. Then, just 200,000 years ago, central chimps got another boost of bonobo genes, the team reports today in Science. In contrast, the western chimp subspecies has no bonobo DNA, the researchers note, suggesting that only those chimps living close to the Congo River entertained bonobo consorts.
Jacinta: What this highlights, more than anything to me, is the importance and excitement of genetic and genomic analyses. Not that we’re experts on the topic, but it has clearly revolutionised the science of evolution, complicating it in quite exciting ways. Think again of those Galapogos finches. Separation, some interbreeding, more separation, less interbreeding, but with a few kinks along the way.
Canto: And we’re just beginning our play with genetics and genomics. There’s surely a lot more to come. Ah, to live forever…
Jacinta: So how did they know some inbreeding occurred? Can we understand the science of this without torturing ourselves?
Canto: David Reich’s book Who we are and how we got here tells the story of interbreeding between human populations, and how population genetics has revolutionised our understanding of the subject. With dread, I’ll try to explain the science behind it. First, the Science article quoted above mentions a split between bonobos and chimps 2 million years ago. Others I’ve noted go back only about a million years – for example a Cambridge University video referenced below. The inference, to me, is that there was a gradual separation over a fair amount of time, as aforementioned. I mean, how long does it take to create a major river? Now, I can’t get hold of the data on chimp-bonobo interbreeding in particular, so I’ll try to describe how geneticists detect interbreeding in general.
I’ll look at the human genome, and I’ll start at the beginning – a very good place to start. This largely comes from Who we are and how we got here, and the following quotes come from that book. The human genome consists of a double chain of 3 billion nucleobases, adenine, cytosine, guanine and thymine. That’s 6 billion bases (often called letters – A, C, G and T) in all. Genes are small sections of this base chain (called DNA), typically a thousand or so letters long. They’re templates or codes for building proteins of many and varied types for doing many different kinds of work, although there are segments in between made up of non-coding DNA.
Researchers have been able to ‘read’ these letters via machinery that creates chemical reactions to specific DNA sequences:
The reactions emit a different colour for each of the letters A, C, G and T, so that the sequence of letters can be scanned into a computer by a camera.
What anthropologists want to focus on are mutations – random errors in the copying process, which tend to occur at a rate of about one in every thousand letters. So, about 3 million differences, or mutations, per genome (3 billion genes, coding or non-coding). But genomes change over time due to these mutations and each individual’s genome is unique. The number of differences between two individuals’ genomes tells us something about their relatedness. The more differences, the less related. And there’s also a more or less constant rate of mutations:
So the density of differences provides a biological stopwatch, a record of how long it has been since key events occurred in the past.
As Reich recounts, it was the analysis of mitochondrial DNA, the tiny proportion of the genome that descends entirely down the maternal line, that became a corner-stone of the out-of-Africa understanding of human origins, which had been competing with the multi-regional hypothesis for decades. ‘Mitochondrial Eve’ – a rather ‘western’ moniker considering that the Adam and Eve myth is only one of a multitude of origin stories – lived in Botswana in Southern Africa about 160,000 to 200,000 years ago, given the variability of the genomic ‘clock’ – the mutation rate.
So, what does this have to do with chimps and bonobos? Well, The exact detail of how Hvilsom et al proved that their (slightly) more recent interbreeding events occurred is hidden behind a paywall, and you could say I’m a cheapskate but the reality is I’m quite poor, trying to bring up seven kids and a few dozen grandkids in a home not much bigger than a toilet, so… but truthfully I’m just getting by, and I just want to know in general the techniques used.
First, they have to find ancient specimens, I think. But, in a video referenced below, they raised the question – Can we ‘excavate’ ancient DNA from modern specimens? We’ve learned that many modern humans have a certain percentage of Neanderthal DNA, say around 2%, but each person’s 2% may be different. Aggregating those different segments can, if we analyse the genomes of enough humans, create a whole Neanderthal genome, though not one of any Neanderthal who ever lived! At least that’s how I’m reading it, in my dilettantish way. So what exactly does this tell us? I’m not at all sure – it’s a relatively new research area, and completely new to me.
The presenter of this video uses the heading, at least at the beginning of his talk, ‘A little Archaic introgression goes a long way’. So now I need to know what introgression means. A quick look-up tells me it’s:
‘the transfer of genetic information from one species to another as a result of hybridization between them and repeated backcrossing‘.
I’ve bolded two key words here. Hybridisation, in mammals, is ‘breeding between two distinct taxonomic units’. Note that the term species isn’t used, presumably because it has long been a questionable or loaded concept – life just seems too complex for such hard and fast divisions. Backcrossing seems self-explanatory. Without looking it up, I’d guess it’s just what we’ve been learning about. Canoodling after speciation should’ve ruled canoodling out.
But, looking it up – not so! It’s apparently not something happening in the real world, something like backsliding. But then… Here’s how Wikipedia puts it:
Backcrossing may be deliberately employed in animals to transfer a desirable trait in an animal of inferior genetic background to an animal of preferable genetic background.
This is unclear, to say the least. How could an animal, even a human, deliberately do this? We could do it to other animals, or try it, based on phenotypes. We’ve been doing that for centuries. What follows makes it more or less clear that this is about human experimentation with other animals, though.
Anyway, I’m going well off-topic here. What I wanted to do is try to understand the proof of, or evidence for, bonobo-chimp interbreeding. I accept that it happened, well after the split between these two very similar-looking species. What could be less surprising? Along the way I’ve been reminded inter alia, of homozygous and heterozygous alleles, but I’ve been frustrated that straightforward information isn’t being made available to the general public, aka myself. I’ll pursue this further in later posts.
Jacinta: What a mess. Phenotype isn’t everything my friend. To a bonobo, a chimp probably looks like a neanderthal – a real bonehead… They probably only had sex with them out of pity. ‘Boys, we’ll show you a good time – like you’ve never had before.’
References
https://www.science.org/content/article/chimps-and-bonobos-had-flings-and-swapped-genes-past
David Reich, Who we are and how we got here, 2018
https://www.newscientist.com/article/2110682-chimps-and-bonobos-interbred-and-exchanged-genes/
love, monogamy, marriage and bonobos
To claim that a union founded on convention has much chance of engendering love is hypocritical; to ask two spouses bound by practical, social and moral ties to satisfy each other sexually for their whole lives is pure absurdity.
Simone de Beauvoir, The Second Sex, p 478.
Discuss…
Canto: So we’re reading Beauvoir’s The second sex, inter alia, and though things have changed a bit in the WEIRD world over the past seventy-odd years, the section titled ‘The Married Woman’ does give something of a historical perspective, via the writings of such males as Montaigne, Balzac, Diderot and Kierkegaard, on the perceived differences between love and marriage and the problems that arise from these differences.
Jacinta: Yes, and marriage and monogamy are something of a mystery, historically, in spite of arguments such as those of Ferdinand Mount in The subversive family, that they are a more or less natural element of human life. We don’t know much about the state of affairs of early Homo sapiens or their ancestors and extinct cousins vis-a-vis monogamy. We do know that our closest living relatives, the bonobos and chimps, aren’t monogamous. And as to the claim, made by some, that humans are meant to be monogamous, that’s of the same type as, say, that humans are meant to be bipedal. No, it’s just something that we evolved to be, as some, but not all of us, socially evolved to be (more or less) monogamous.
Jacinta: The question is when? I suppose an obvious answer is when the concept of property became important, and the handing down of property to offspring. So that families started to become powerful rather than individuals. The beginnings of agriculture?
Canto: Some say division of labour may have played a part, though I’m not sure why…
Jacinta: Scientific American has an interesting online article from a few years ago reporting on studies that ‘aimed to find the best explanation for monogamy among three persistent hypotheses: female spacing, infanticide avoidance and male parental care’. So female spacing is just what it says: according to SciAm:
The female-spacing hypothesis posits that monogamy arises after females begin to establish larger territories to gain more access to limited food resources and, in the process, put more distance between one another. With females farther apart, males have a harder time finding and keeping multiple mates. Settling down with a single partner makes life easier, reducing a male’s risk of being injured while patrolling his territory and enabling him to ensure that his mate’s offspring are his own.
Canto: Females began to do that? In the bonobo world, female closeness was the key to their success – the females I mean, but perhaps also bonobos in general. It seems to me more likely that women would work in teams, helping each other to find and exploit resources, or am I being too hippy-happy-clappy?
Jacinta: Yeah maybe, but I note also the assumption here that males would have a hard time keeping multiple mates – the assumption being that early humans were already male-dominated.
Canto: Yes that quoted paragraph is all about the males… though to be fair most primate species are male-dominated. Still, one can’t assume…
Jacinta: Well, the proponents of this hypothesis did a statistical analysis of couple of thousand mammalian species, and found, apparently, that they started out solitary, but many, or some, switched to monogamy during their evolutionary history. How they proved that I’m not sure. They claimed that ‘monogamy most frequently occurred in carnivores and primates…’
Canto: Hang on. Isn’t it true that most primates are not monogamous?
Jacinta: Ahh, you’re probably thinking only of apes. There are hundreds of primate species, and they’re still being discovered. Three more were added in the last couple of years.
Canto: Shit! It’s all so hard to keep up with.
Jacinta: Lorises and lemurs, tarsiers and hatfuls of monkeys. Simians and prosimians, old world and new world, greater and lesser apes, etc. And actually, most primates are monogamous.
Canto: Well, I don’t think we should let it bother or constrain us. If we don’t feel monogamous, I mean individually speaking, we don’t have to be so.
Jacinta: But there are social constraints. They’ve loosened, no doubt, in the WEIRD world, but they’re there still. Besides, it’s convenient to settle down with one person, especially as you get older. It’s hard work trying to impress one partner after another into canoodling, what with rivalries and jealousies, and children who end up not knowing who’s what.
Canto: Well, yes – it does spice up life a bit, but too much spice can be overly acidic, or something. Still, I cling hopefully to the bonobo way…
Jacinta: Anyway, let’s get back to the second hypothesis – infanticide avoidance. I don’t think there’s much in this, re humans, but here’s the rationale:
Primates are uniquely at risk for infanticide: they have big brains that need time to develop, which leaves babies dependent and vulnerable for long periods after birth. And the killing of babies has been observed in more than 50 primate species; it typically involves a male from outside a group attacking an unweaned infant in a bid for dominance or access to females.
I suppose early hominids lived in smallish groups, like troupes of other primates, and I never considered that there’d be an alpha male among them, but I suppose it makes sense. But the bonobo part of me is in denial….
Canto: Well, warfare goes back a long way and capturing and raping women has always gone along with that, and it’s often been about capturing and expanding territory – e.g. Putin and Ukraine – and in those earlier times when resources were scarcer and harder-won, children, that’s to say the children of the defeated, would’ve been a burden. And the winners knew they could make more of their own with the captive women. It’s all quite plausible. I saw it in Empress Ki!
Jacinta: Hmmm. Having it off with captive women – essentially rape – doesn’t really fit with monogamy. In those Korean historicals you love there are wives and also concubines, and your alpha-maledom would be defined by the number of concubines you commanded, I’m guessing. So the male parental care hypothesis is most palatable to us moderns, I hope. Here’s what the SciAm site says:
When a baby becomes too costly in terms of calories and energy for a mother to raise on her own, the father who stays with the family and provides food or other forms of care increases his offspring’s chances of survival and encourages closer ties with the mother. A related idea… holds that the mere carrying of offspring by fathers fosters monogamy. Mothers have to meet the considerable nutritional demands of nursing infants. Yet for primates and human hunter-gatherers, hauling an infant, especially without the benefit of a sling or other restraint, required an expense of energy comparable to breast-feeding. Carrying by males could have freed females to fulfill their own energetic needs by foraging.
Canto: Yes, that’s a much more Dr Feelgood hypothesis, but interestingly this assumes an understanding of the relationship between sex and offspring. Males wouldn’t want to be caring for someone else’s kids, would they? And I’m sure I read somewhere that even some cultures living today, or at least not so long ago, aren’t clear about that relationship.
Jacinta: Well, and yet I’ve heard that bonobo females try to control who their adult sons mate with, as if they have an inkling… Bronislaw Malinowski (the first anthropologist I ever heard of) claimed that Trobriand Islanders thought that males played no role in producing children, but that’s been found to be a bit questionable. Seems plausible to me though. And something to aim for.
Canto: One thing anthropologists seem to say nothing about in these reflections on monogamy is love. This eternal bonding force that unites Romeo and Juliet, Antony and Cleo, Sonny and Cher…
Jacinta: Yeah, hormones they say. And when offspring come along, a certain force of duty, often reinforced by the community, or the State. So the male parent ends up staying, not really knowing whether it’s because he wants to or not. And one of the forces, a principle force, is societal, or cultural. He sees pairings-off all around him, physically reinforced by separate houses, fenced in. It’s the ‘norm’. With bonobos, no physical or, apparently, ethical barriers have been erected against polyandry/polygyny – to use human terms that would be meaningless to them. Does that mean no love? Of course not – on the contrary, our cousins can still teach us a thing or two about love…
References
Simone de Beauvoir, The Second Sex, 1949
Ferdinand Mount, The subversive family, 1982
https://www.scientificamerican.com/article/human-monogamy-has-deep-roots/
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/
a bonobo world 36: there is no bonobo nation
nations, some say
Homo sapiens have been around for between 200 and 300 thousand years, depending on various theories and interpretations. I always like to point out that the ‘first’ H sapiens had parents and grandparents, who wouldn’t have noticed any difference between junior and themselves, so when does a new species actually begin?
Leaving that thorny problem, I’ll turn to another – when did the first nation begin? My uneducated conjecture is that it was an evolving concept, post-dating the evolution of human language, and we have little idea about when that process was completed, at least to the point where we could conceptualise and communicate such ideas. Modern nations, with boundaries, checkpoints, passports and state paraphernalia, are of course ultra-new, with some fresh ones popping up in my lifetime, but I’ve heard Australian Aboriginal language groups described as nations, with the first of these H sapiens arriving here around 65,000 years ago, according to the National Museum of Australia. Of course they wouldn’t have arrived here as nations, however defined, so when did they become such? Bill Gammage, in The biggest estate on earth: how Aborigines made Australia, makes this point at the outset:
Hundreds of pages try to define Aboriginal social units (tribe, horde, clan, mob, language group, family, kin) without achieving clarity or consensus.
So is this a silly question? Surely not, since the term ‘First Nations’ has gained currency in recent decades. Rather bizarrely, the Wikipedia article on First Nations focuses solely on the early inhabitants of what is now Canada. This is presumably because these people are recognised as such by the Canadian government, at least for statistical reasons. In any case, these early people of North America, Australia and elsewhere mostly didn’t use writing, and their doubtless various self-references might be translated by us, at their bidding, as nations, but it’s clear that using such a term adds a certain gloss borrowed from modern lingo. Gammage does the same thing, perhaps justifiably, in referring to Aboriginal Australia as an estate, a term which I tend to associate with snotty landowners and gated communities. However, it also puts the focus on land, rather than people.
We’ve come to associate nationhood with progress, civilisation and sophistication. No wonder the Kurds, the Basques and other cultural-linguistic groups are striving for it, and in particular for land on which to fix these qualities. The progression appears to go from group – as with chimps, bonobos and no doubt early hominids – to tribe, to settlement, to a collection of settlements or villages, to a centralised, sort of inward-facing region of shared culture, flourishing up to a civilisation of sorts. So it starts, for us, with our common ancestry with our primate cousins.
We know that chimps and gorillas separate into groups that control particular territories, but if these groups are too small or avoid interaction with other groups, inbreeding will become a problem. This problem, which confronts all social species, can be solved by male or female dispersal – that’s to say, by breeding or ready-to-breed young adults flitting from their natal group to a neighbouring one. But moving to a new, unfamiliar neighbourhood might be as fraught, or more so, for non-human species as it is for us. According to an article published by the Royal Society in 2017, when there are limited opportunities for dispersal, many species appear to have a behavioural avoidance pattern to prevent inbreeding. For example, closely related elephants avoid mating altogether. In other species, they manage to mate without producing offspring, or produce healthy offspring even where the chances of inbreeding would seem to be high.
We often make jokes about human inbreeding, especially with island populations (Tasmanians are sometimes targeted), but there are real issues with inward, ultra-nationalist thinking, which can lead to a kind of cultural inbreeding. This can even transcend nations, as with the touting of ‘Asian values’. Considering that millions of Asians have paired up with non-Asians, this might pose a problem for the offspring, if such notions were taken seriously.
Anyway, my own view of nations, for what it’s worth, is that that they’ve become a useful mechanism for divvying up land into states. Land has been an essential feature of human culture – this land is my land, this land is your land, this land is made for you and me. The obsession humans have with the myth of land ownership is something I’ve often found rather comical. I won’t go into the shenanigans around Antarctica, but I’ll relate a couple of illustrative anecdotes.
In my boisterous youth I accompanied a couple of housemates in visiting a nearby tennis court, which I’d previously noticed was surrounded by the usual high, open-wire fencing, but fronted by an unlocked gate. On the far side of the court were the vast sporting fields of St Peter’s College, one of the most exclusive private schools in the city, and beyond that, the imposing buildings of that august institution. I’d persuaded my housemates to take our racquets over for a fun hit out, though there was no net, and we only had two racquets between three. So we’d been at it for about 15 minutes when I spotted a figure marching towards us across the sward. As he closed in, I took note of the tweed jacket, the flapping flag of his woollen scarf, the swept-back, neatly combed blonde hair. I won’t try to mimic his accent or recall his exact words – distance lends a certain enchantment to the view – but there was no forgetting his sense of complete outrage. ‘Excuse me boys, but you must realise that this is PRIVATE PROPERTY!’ Those last two words are the only ones I’m certain of.
I spent the next few weeks daydreaming of hoisting this gentleman by his own petard, but also reflecting on the quasi-religious power of landed property. It was exactly as if we’d abused, or worse, denied, someone’s god.
Another incident was much more recent. An Aboriginal woman complained to me on the street that I – meaning we ‘whites’ – were on her land. I responded to her, perhaps in a frustrated tone, that land was land, it belonged to itself. This wasn’t particularly articulate, but she didn’t have any response. I suppose what I meant was that the Earth’s land, ever changing, shifting and subducting, had been around for billions of years, and for most of human existence we thought no more of land ownership than did the animals we hunted. How things have changed.
Of course, nationalism is not going away any time soon, and I’m prepared to make my peace with it. States have their obvious uses, in binding a smaller proportion of the human population together via laws, economic co-operation and political policies. The Einsteinian dream of a world government is unworkable, and the United Nations still needs a lot of work, though it has been beneficial on balance, especially via its ancillary organisations. The problem of course is ultranationalism, in both its outward expansionist form, and its inward-facing exclusivity and xenophobia. Diversity, or variety, is obviously a good thing, whether in diet, industry, arts or genetics. My own modest experience in teaching students from scores of nations tells me that Homo sapiens, like Pan paniscus, are one people, with similar interests, in laughing, loving, wondering and striving for more. Our strivings and problems are much more global than national – a veritable internet of interests. I hope that this realisation is growing.
References
https://aiatsis.gov.au/explore/map-indigenous-australia
https://en.wikipedia.org/wiki/First_Nations
https://royalsocietypublishing.org/doi/full/10.1098/rsos.160422
Bill Gammage, The biggest estate on Earth: how Aborigines made Australia, 2012.