an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

Archive for the ‘behaviour’ Category

Tanah Papua, the bird paradise

leave a comment »

There are few simple pleasures to compare with watching birds of paradise display and perform, even if it’s only on video – and it would be pretty hard to see them otherwise. The forests of Papua are a wonderland for birds, and 39 of the 42 known species of birds of paradise are found only there. My attention was drawn to these very striking birds – in their very various ways – when I read Peter Raby’s biography of Alfred Russel Wallace several years ago, and I’ve associated them with exotic forest regions, miserable weather, malaria and an almost toxic other-worldliness ever since. A sort of anti-paradise doused with bewildering colour and cacophony.

The lineage of these birds has been hard to reconstruct, and apparent similarities to other birds, such as bower birds, have led ornithologists astray in the past. And to be scientific about it all, I’d have to master such concepts as order, family and clade, but I won’t go there in this post, except to say that the whole classification system looks a mess from the outside.. The most recent mitochondrial DNA research has set their ‘moment’ of emergence at about 24 million years ago. They’re quite close, genetically, to corvids, always a plus.

king bird of paradise (cincinnurus regius)

To an amateur, the most striking features of these birds are the plumage and displays of the males. And the females surely agree, even when they try to appear unimpressed. One immediately thinks of sexual selection – and Darwin. Here’s what Darwin had to say about the process, in The Origin of Species:

Sexual selection… depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring.

…when the males and females of any animal have the same general habits… but differ in structure, colour or ornament, such differences have been mainly caused by sexual selection

On the origin of species, 1st edition, pp88,89

One has to wonder why it’s the males who grow their weird and wonderful plumage and create their elaborate dances to attract the females, and not the other way around. Generally the female coloration – and that of both sexes when young – has evolved so that they match and blend in with their surroundings. The males are taking serious risks in drawing attention to themselves in this way, which is why the differences appear late – as secondary sexual characteristics. In fact, males generally mature later than females, by quite a wide margin. But since they don’t bear the offspring the males are more dispensable. It’s interesting to note, in this light, that in polygamous species, birds are sexually dimorphic both in appearance and lifespan. That’s to say, monogamous birds tend to look alike and to have the same lifespans, whereas in polygamous species, the females live longer. In fact this is the case in all species, not just birds. The San Diego zoo, which specialises in this family, tells us that birds of paradise can live for some 30 years in captivity – but surely it would be tougher in the wild, especially for males.

Not all birds of paradise are polygamous though – they have a range of breeding systems, of which the most interesting is ‘lek-type polygamy’. Lek is a Swedish term which refers to fun activity bound by the loosest of rules. It was first used in a book about the avian life of that region back in the 1860s, and is now adopted worldwide, and applies to a bewildering variety of species, including birds, bees, butterflies and bats (and various species of reptiles, amphibians and fish). And not just because they all like to have fun; the term has been refined to refer to specific behaviours. Two general types of lekking are identified – classic and exploded. They refer essentially to the physical space occupied – the lek. In a classic lek (a more or less circular region), each of the males is within sight of at least some of the others, whereas in an exploded lek, this isn’t ‘necessary’, as long as they’re in earshot. In fact, with some booming birds, like the New Zealand kakapo, they can be kilometres apart. In these exploded leks, the variety of behaviours is greater, as if the woo-ers are less inhibited by their neighbours.

Of course the leks in thickly forested Papua would be very different from Sweden. Sometimes the males share and compete in a common ground such as a forest clearing, while in other species they display and dance in the trees, controlling their territory vocally. Displays involve spinning, charging, freezing, hopping and skipping, hanging upside down, making show of their most irridescent plumes, all the kind of stuff imitated by the Folies Bergère, but with males rather than females as the beauties.

Breeding behaviour, though, is very varied. Not all male species are brightly festooned, and male-female relations run from bim-bam-thanks-mam polygamy to the sharing of nest-building and child-rearing among monogamous species such as the manucodes (they don’t all bear the bird-of paradise name – apart from manucodes there are sicklebills, riflebirds, parodias, astrapias and others).

splendid astrapia (astrapia splendidissima)

These birds are, unsurprisingly, and more than other types, very much tree-dwellers, preferring the high canopies and living largely off their fruits, so they need to have their forests protected. They’ve been hunted for centuries, and Wallace had no hesitation in killing as many as he could himself in the 1850s. Of course, being in straitened circs in those years, his income was largely dependent on producing exotic specimens for the home trade, and birds of paradise were like gold. But local tribesmen also valued the bright plumage as a status symbol. In recent times the popularity of the birds for twitchers has helped in their protection.

They’re a fairly raucous lot, and the striking, machine-like notes of riflebirds and sicklebills are very much worth listening to online. One might assume that in dense forest, loud calls to indicate location are a must.

magnificent riflebirds (ptilorus magnificus)

In conclusion, I began writing this to find out more about a particular family of birds, but got sidetracked by a lot of fascinating stuff I’ve only touched upon here, such as sexual selection, sexual dimorphism and anisogamy. More about all that in later posts, I hope.

Written by stewart henderson

July 28, 2019 at 1:24 pm

discussing mental health and illness

leave a comment »

Canto: I’ve been told I’m on the autism spectrum, by someone who’s not on it, presumably, but who’s also not an expert on such things, but I’m not sure who is.

Jacinta: Well of course we’re all on the autism spectrum, it depends on your location on it, I suppose, if you need to worry. ‘You’re sick’ is one of the oldest lines of abuse, but I’m reminded of a passage in The moral landscape, which I’m currently rereading. He describes a funny-but-not-so-funny piece of research by one D L Rosenhan:

… in which he and seven confederates had themselves committed to psychiatric hospitals in five different states in an effort to determine whether mental health professionals could detect the presence of the sane among the mentally ill. In order to get committed, each researcher complained of hearing a voice repeating the words ’empty’, ‘hollow and ‘thud’. Beyond that, each behaved perfectly normally. Upon winning admission to the psychiatric ward, the pseudo-patients stopped complaining of their symptoms and immediately sought to convince the doctors, nurses and staff that they felt fine and were fit to be released. This proved surprisingly difficult. While these genuinely sane patients wanted to leave the hospital, repeatedly declared that they experienced no symptoms, and became ‘paragons of cooperation’, their average length of hospitalisation was 19 days (ranging from 7 to 52 days), during which they were bombarded with an astounding range of powerful drugs (which they discreetly deposited in the toilet. None were pronounced healthy. Each was ultimately discharged with a diagnosis of schizophrenia ‘in remission’ (with the exception of one who received a diagnosis of bipolar disorder). Interestingly, while the doctors, nurses and staff were apparently blind to the presence of normal people on the ward, actual mental patients frequently remarked on the obvious sanity of the researchers, saying things like ‘You’re not crazy – you’re a journalist’.

S. Harris, The moral landscape, p142

Canto: Well, that’s a fascinating story, but let’s get skeptical. Has that study been replicated? We know how rarely that happens. And there are quite a few other questions worth asking. Wouldn’t most of the staff etc have been primed to assume these patients had a genuine mental illness? And surely only a small percentage would have had the authority to make a decision either way. Who exactly had them committed, what was the process, and what was the relationship between those doing the diagnosis and those engaging in treatment and daily care? Was there any fudging on the part of the pseudo-patients (who were apparently also the researchers) in order to prove their point (which presumably was that mental illness can be easily shammed)? And wouldn’t you expect other patients, many of whom wouldn’t believe in their own mental problems, to be supportive of the sanity of those around them?

Jacinta: Okay, those are some valid points, but are you prepared to accept that a lot of these mental conditions, such as bipolar disorder, borderline personality disorder (the name speaks volumes), attention deficit disorder, narcissistic whatever disorder and so on, are a little flakey around the edges?

Canto: Maybe, but with solid centres I’m sure. Depression is probably the most common of those mental conditions, and too much skepticism on that count could obviously lead to disaster. Take the case of South Korea, which has one of the highest suicide rates in the world. There appears to be a nationwide skepticism about mental health issues there, which clashes with high stress levels to create a crisis of care. Professional help is rarely sought and isn’t widely available. It raises the question of the value of skepticism in some areas.

Jacinta: I wonder if the rapid advances in neurophysiology can help us here. Mental health is all about the brain. In the above quote, the pseudo-patients were mostly diagnosed with schizophrenia. That’s surprising. In my naïveté I would’ve thought there was a neurological test for schizophrenia by now.

Canto: Well, the experiment described in The moral landscape dates from the early seventies, but currently there’s still no diagnostic test for schizophrenia based on the brain itself, it’s all about such symptoms as specific delusions and hallucinations, which could still be shammed I suppose, if anyone wanted to. But what about borderline personality disorder – I was told recently that it’s very real, in spite of the name.

Jacinta: Well, there appears to be a mystery about the causes, and a general confusion about the symptoms, which seem to be rather wide-ranging – though I suppose if a patient displays several of them you can safely conclude that she’s stark staring bonkers.

Canto: Yes that’s a thing about mental illness, quite seriously. You don’t need to be an expert to notice when people are behaving in a way that’s detrimental to themselves and others, especially if it’s a sharp deviation from previous behaviour. And if it’s a slow descent, as quite often depression can be, it’s harder to pick from that person’s standard lugubrious personality, so to speak. And in the end, maybe the labelling isn’t so important as the help and the treatment. But then, people love a label – they want to know precisely what’s wrong with them.

Jacinta: I suppose the difficulty with mental illness and labelling, as opposed to labelling other more ‘physical’ illnesses or injuries, is the near-ineffable complexity of the brain. For example, I notice that among the symptoms of borderline personality disorder are apparent behaviours that don’t really cohere in any way. This site places the symptom of uncertainty and indecisiveness along with extreme risk-taking and impulsiveness, and then there is fear of abandonment, and other odd behaviours which seem to head in different directions, seeming to have one thing alone in common – being extreme or abnormal.

Canto: Yes, again, behaviour that tends to harm the self or others.

Jacinta: At the moment, I think there are still too few connections between neurology and psychiatry and the treatment of mental illness, though it’s a matter of enormous complexity. I had thought, for example, that the role of the neurotransmitter dopamine was essential to our understanding of schizophrenia, but more recent research has found that the neurochemistry of the condition involves many other factors, including glutamate, GABA, acetylcholine and serotonin. There’s so much more work to be done. But we also need to be very aware of the social and cultural conditions that tip people over the edge into mental illness. Changes in the way our brain is functioning might be seen as proximal causes of an increase in depression and suicide, but it’s more likely that the ultimate causes have to do with the stresses that particular organisations, societies and cultures impose upon us.

Written by stewart henderson

June 30, 2019 at 12:45 pm

kin selection – some fascinating stuff

leave a comment »

meerkats get together for ye olde family snap

Canto: So we’ve done four blogs on Palestine and we’ve barely scratched the surface, but we’re having trouble going forward with that project because, frankly, it’s so depressing and anger-inducing that it’s affecting our well-being.

Jacinta: Yes, an undoubtedly selfish excuse, but we do plan to go on with that project – we’re definitely not abandoning it, and meanwhile we should recommend such books as Tears for Tarshiha by the Palestinian peace activist Olfat Mahmoud, and Goliath by the Jewish American journalist Max Blumenthal, which highlight the sufferings of Palestinian people in diaspora, and the major stresses of trying to exist under zionist monoculturalism. But for now, something completely different, we’re going to delve into the fascinating facts around kin selection, with thanks to Robert Sapolski’s landmark book Behave. 

Canto: The term ‘kin selection’ was first used by John Maynard Smith in the early sixties but it was first mooted by Darwin (who got it right about honey bees), and its mathematics were worked out back in the 1930s. 

Jacinta: What’s immediately interesting to me is that we humans tend to think we alone know who our kin are, especially our extended or most distant kin, because only we know about aunties, uncles and second and third cousins. We have language and writing and record-keeping, so we can keep track of those things as no other creatures can. But it’s our genes that are the key to kin selection, not our brains.

Canto: Yes, and let’s start with distinguishing between kin selection and group selection, which Sapolsky deals with well. Group selection, popularised in the sixties by the evolutionary biologist V C Wynne-Edwards and by the US TV program Wild Kingdom, which I remember well, was the view that individuals behaved, sometimes or often, for the good of the species rather than for themselves as individuals of that species. However, every case that seemed to illustrate group selection behaviour could easily be interpreted otherwise. Take the case of ‘eusocial’ insects such as ants and bees, where most individuals don’t reproduce. This was seen as a prime case of group selection, where individuals sacrifice themselves for the sake of the highly reproductive queen. However, as evolutionary biologists George Williams and W D Hamilton later showed, eusocial insects have a unique genetic system in which they are all more or less equally ‘kin’, so it’s really another form of kin selection. This eusociality exists in some mammals too, such as mole rats. 

Jacinta: The famous primatologist Sarah Hrdy dealt something of a death-blow to group selection in the seventies by observing that male langur monkeys in India commit infanticide with some regularity, and, more importantly, she worked out why. Langurs live in groups with one resident male to a bunch of females, with whom he makes babies. Meanwhile the other males tend to hang around in groups brooding instead of breeding, and infighting. Eventually, one of this male gang feels powerful enough to challenge the resident male. If he wins, he takes over the female group, and their babies. He knows they’re not his, and his time is short before he gets booted out by the next tough guy. Further, the females aren’t ovulating because they’re nursing their kids. The whole aim is to pass on his genes (this is individual rather than kin selection), so his best course of action is to kill the babs, get the females ovulating as quickly as possible, and impregnate them himself. 

Canto: Yes, but it gets more complicated, because the females have just as much interest in passing on their genes as the male, and a bird in the hand is worth two in the bush…

Jacinta: Let me see, a babe in your arms is worth a thousand erections?

Canto: More or less precisely. So they fight the male to protect their infants, and can even go into ‘fake’ estrus, and mate with the male, fooling the dumb cluck into thinking he’s a daddy. 

Jacinta: And since Hrdy’s work, infanticide of this kind has been documented in well over 100 species, even though it can sometimes threaten the species’ survival, as in the case of mountain gorillas. So much for group selection.

Canto: So now to kin selection. Here are some facts. If you have an identical twin your genome is identical with hers. If you have a full sibling you’re sharing 50% and with a half-sibling 25%. As you can see, the mathematics of genes and relatedness can be widened out to great degrees of complexity. And since this is all about passing on all, or most, or some of your genes, it means that ‘in countless species, whom you co-operate with, compete with, or mate with depends on their degree of relatedness to you’, to quote Sapolsky. 

Jacinta: Yes, so here’s a term to introduce and then fairly promptly forget about: allomothering. This is when a mother of a newborn enlists the assistance of another female in the process of child-rearing. It’s a commonplace among primate species, but also occurs in many bird species. The mother herself benefits from an occasional rest, and the allomother, more often than not a younger relation such as the mother’s kid sister, gets to practice mothering. 

Canto: So this is part of what is called ‘inclusive fitness’, where, in this case, the kid gets all-day mothering (if of varying quality) the kid sister gets to learn about mothering, thereby increasing her fitness when the time comes, and the mother gets a rest to recharge her batteries for future mothering. It’s hopefully win-win-win. 

Jacinta: Yes, there are negatives and positives to altruistic behaviour, but according to Hamilton’s Rule, r.B > C, kin selection favours altruism when the reproductive success of relatives is greater than the cost to the altruistic individual. 

Canto: To explain that rule, r equals degree of relatedness between the altruist and the beneficiary (aka coefficient of relatedness), B is the benefit (measured in offspring) to the recipient, and C is the cost to the altruist. What interests me most, though, about this kin stuff, is how other, dumb primates know who is their kin. Sapolsky describes experiments with wild vervet monkeys by Dorothy Cheney and Robert Seyfarth which show that if monkey A behaves badly to monkey B, this will adversely affect B’s behaviour towards A’s relatives, as well as B’s relatives’ behaviour to A, as well as B’s relatives’ behaviour to A’s relatives. How do they all know who those relatives are? Good question. The same researchers proved this recognition by playing a recording of a juvenile distress call to a group of monkeys hanging around. The female monkeys all looked at the mother of the owner of that distress call to see what she would do. And there were other experiments of the sort. 

Jacinta: And even when we can’t prove knowledge of kin relations (kin recognition) among the studied animals, we find their actual behaviour tends always to conform to Hamilton’s Rule. Or almost always… In any case there are probably other cues, including odours, which may be unconsciously sensed, which might aid in inclusive fitness and also avoiding inbreeding. 

Canto: Yes and It’s interesting how this closeness, this familiarity, breeds contempt in some ways. Among humans too. Well, maybe not contempt but we tend not to be sexually attracted to those we grow up with and, for example, take baths with as kids, whether or not they’re related to us. But I suppose that has nothing to do with kin selection. And yet…

Jacinta: And yet it’s more often than not siblings or kin that we have baths with. As kids. But getting back to odours, we have more detail about that, as described in Sapolski. Place a mouse in an enclosed space, then introduce two other mice, one unrelated to her, another a full sister from another litter, never encountered before. The mouse will hang out with the sister. This is called innate recognition, and it’s due to olfactory signatures. Pheromones. From proteins which come from genes in the major histocompatibility complex (MHC). 

Canto: Histowhat?

Jacinta: Okay, you know histology is the study of bodily tissues, so think of the compatibility or otherwise of tissues that come into contact. Immunology.  Recognising friend or foe, at the cellular, subcellular level. The MHC, this cluster of genes, kicks off the production of proteins which produce pheromones with a unique odour, and because your relatives have similar MHC genes, they’re treated as friends because they have a similar olfactory signature. Which doesn’t mean the other mouse in the enclosure is treated as a foe. It’s a mouse, after all. But other animals have their own olfactory signatures, and that’s another story. 

Canto: And there are other forms of kin recognition. Get this – birds recognise their parents from the songs sung to them before they were hatched. Birds have distinctive songs, passed down from father to son, since its mostly the males that do the singing. And as you get to more complex species, such as primates – though maybe they’re not all as complex as some bird species – there might even be a bit of reasoning involved, or at least consciousness of what’s going on. 

Jacinta: So that’s kin selection, but can’t we superior humans rise above that sort of thing? Australians marry Japanese, or have close friendships with Nigerians, at least sometimes. 

Canto: Sometimes, and this is the point. Kinship selection is an important factor in shaping behaviour and relations, but it’s one of a multiple of factors, and they all have differential influences in different individuals. It’s just that such influences may go below the level of awareness, and being aware of the factors shaping our behaviour is always the key, if we want to understand ourselves and everyone else, human or non-human.

Jacinta: Good to stop there. As we’ve said, much of our understanding has come from reading Sapolsky’s Behave, because we’re old-fashioned types who still read books, but I’ve just discovered that there’s a whole series of lectures by Sapolsky, about 25, on human behaviour, which employs the same structure as the book (which is clearly based on the lectures), and is available on youtube here. So all that’s highly recommended, and we’ll be watching them.

References

R Sapolski, Behave: the biology of humans at our best and worst. Bodley Head, 2017

https://www.britannica.com/science/animal-behavior/Function#ref1043131

https://en.wikipedia.org/wiki/Kin_selection

https://en.wikipedia.org/wiki/Eusociality

 

 

 

 

 

women and warfare, part 1: humans, chimpanzees and patriarchy

leave a comment »

Recently listened to a bit of historian Margaret McMillan, along with some military reps, on the radio talking about warfare past and future. It was recorded during a public talk on the topic. I’ve got her book, The Uses and Abuses of History, which I’ve only just started to read, but I was struck by her pessimistic attitude. Of course she’s right to say that warfare isn’t about to disappear, and dog knows we have a proliferation of macho thugs on the global scene at present, but her somewhat dismissive description of Pinker’s thesis, that the world is getting less violent, rather irked me. She described the thesis as ‘persuasive but too positive’ or some such term (which struck me as odd if not disingenuous – obviously she wasn’t persuaded). To me, considering that, almost to the end of the nineteenth century, warfare was a way of life for many a European male, and that the so-called Great War showed so many people how disastrous zero-sum game nationalism and one-eyed patriotism can be, and how far we have come, generally, from seeing other cultures as ‘savage’ or backward, and especially how far we have progressed in multiculturalism over the past century or so, I can’t accept that we haven’t made great strides in reducing warfare among civilised nations in the 20th century and beyond. Not, of course, without great cost, in the early half of that century especially.

But it was a response during question time that has prompted me to write. MacMillan was asked whether things would be better if, say, the US President was a woman, or some such thing. Anyway the gist of the question was whether warfare would be reduced if women were in charge. Macmillan was again sceptical/pessimistic, citing Indira Ghandi’s record as India’s PM. Of course she could’ve cited others, like Margaret Thatcher, or even Aung San Suu Kyi, the Nobel Peace prizewinner who’s been so much under fire for Burma’s treatment of its Rohingya population. But I found this response to be shallow and fatuous. The case of Aung San Suu Kyi is most telling – she’s largely a captive of the all-male military, all Buddhists like the all-male monks who’ve been most active in the Rohingya persecutions. But it’s the same for all female heads of state. Their cabinets and their political advisers are overwhelmingly male, they have to deal with a military sector which is entirely male, and a business sector which is much the same. All the power in all the lands you care to mention is massively male. Massively. In order to seriously answer the question ‘What if women were in charge?’ you have to imagine a ‘world turned upside down’. Anything less, as I say, would be a fatuous and shallow response. You would have to imagine a world with a more or less all-female political-military-business sector. And if you think that’s crazy, why don’t you think the current more or less all-male power situation is crazy?

The fact is that statistically, women are less aggressive than men. We can go into all sorts of genetic, hormonal, cultural and environmental reasons for this – and it’s important to explore all of that – but the fact itself is undeniable. It also appears that women are more collaborative – more able to work especially with other women. Of course women can be aggressive and highly competitive – I love women’s sports, but I notice that in women’s soccer and basketball I’ve never once seen the kind of all-in biffo that quite regularly spoils the men’s version of these sports. This is no accident.

Wars in the past have always been associated with manliness – not just physical warfare, but the kind of business and political warfare that Trump – the archetypal wannabe macho ‘winner’ – engages in. And in an increasingly interconnected and inter-reliant global scenario, this kind of warfare is proving more and more counter-productive.

I believe that one day – though hardly in the near future – we will socially evolve, out of sheer necessity, into civilisations in which women hold the balance of power. It won’t simply be a ‘world turned upside down’ but more like a move from chimp-like society to bonobo-like society. I’ve held this view for a long time but I’ve hardly dared express it. Luckily, so few people read my writing that I’m unlikely to experience much blowback, but in any case many would argue that it’s illegitimate to compare humans with other species. Not just because of the essentially religious idea of ‘human specialness’, but because ‘civilisation’ or ‘culture’ have so altered the human psyche that it’s essentially useless to compare us with species that either don’t have culture or have it in only the most rudimentary form.

I doubt if Darwin would agree, as much of his work focussed on the extraordinary complexity of non-human species, and the ‘instinctiveness’ of humans. In any case I’ll focus now on other primates, all of whom are socially organised in one way or another.

The lemurs of Madagascar are prosimians, species of primates that are considered less ‘evolved’ than simians. Outside of their current island home, lemurs were out-competed by the more adapted species they gave rise to. Fascinatingly, all lemur species are female-dominant, though not always through sexual dimorphism. Lemurs live in small groups, with a generally even male-female ratio. A key feature of lemur social life is the creation of coalitions, especially as regards sexual behaviour, and sexual behaviour, obviously, is key to any species’ survival and development. The lemurs are something of a mystery in regard to their female-dominant traits, which has even given rise to a slightly pejorative title for the mystery – the lemur syndrome. In any case, understanding their group dynamics, involving coalitions, competition and sex, inter alia, and linking this behaviour to genes, gene expression and neurological findings – which are being increasingly honed and targeted – is essential to solving the mystery.

The same goes, of course, for all prosimian and simian species. The vast majority of them are male-dominant, often, but not always reflected in a greater or lesser degree of sexual dimorphism. Size isn’t everything in species with complex and sometimes gender-based group dynamics. And so I come to that old favourite topic, chimps and bonobos, our equal-closest living relatives.

Chimps can be violent towards each other, often to a sickening degree – almost as sickening as humans – but, as with humans, this violence is clearly not ultimately self-destructive. For example, when a gang of chimps come across a stray member of a neighbouring group, it’s not uncommon for them to bite, kick and stomp the unfortunate to death. There have even been occasions when one group has slaughtered another wholesale, though one or two might survive by flight – and again, human comparisons spring to mind.

Chimps live in fission-fusion social groups, meaning that they form small, relatively unstable groups within a larger association which may amount to hundreds. Within these groups, large or small, there is a male linear dominance hierarchy, in which the group has one alpha male, who dominates all the others, followed by a beta male, who dominates everyone but the alpha, and so on down the line. Males remain in their birth communities, but females emigrate more or less at adolescence. This means that the young females entering a new group are of lower status and are viewed with suspicion (think of refugees at the US southern border). It also means that the females break kinship ties more than the males. Males also bond through co-operative hunting and boundary patrolling, and in attacking other groups. Again, think of human tribal behaviour. In some chimp communities kinship has been observed to be more important than other coalitions, in others not, but in either case male bonding adds to dominance over females. Co-operative hunting, it should be added, is having serious effects on the hunted, which is usually the red colobus monkey, which is in serious decline in multiple sites where chimps are thriving.

There is always one power that females have in these societies, the power to produce offspring – to maintain the species. Estrus in chimps is marked by visible swelling of the anogenital region, though the first of these swellings occurs before the young female is fertile, and may be a way of attracting males in her new community. Females are able to give birth (parturition) at 13-14 years, but if they aren’t accepted in the community, there’s a danger of infanticide by males, especially as females often use promiscuity to establish themselves. Infanticide tends to reduce the female’s interbirth interval, and favours the genetic line of the male doing the killing (one wonders if they have a way of ‘knowing’ that the murdered child isn’t theirs). Chimp sexual activity is generally promiscuous, though it most often occurs during estrus (maximal tumescence). The female, of course, has to strategise to find the best opportunity for producing healthy and communally favoured offspring – not an easy task, as it leads to secretiveness, suspicion, jealousy and so forth.

Of course, I’m writing this to draw comparisons between chimp societies and early human societies, out of which our modern civilisations developed. Human societies are more complex, naturally, reflecting individual, neurological complexity, and greater, more diverse cultural complexity, but the basis of our patriarchy can certainly be traced in our chimp relatives. Bonobos, however, are quite different, and remarkably so considering their relatively recent divergence from their chimp cousins. Humans have one great advantage over chimps and bonobos, I think. We can consciously teach ourselves to change, to be better adapted to a biosphere we have increasingly recognised is interdependent and precious in its astonishing diversity. And we can learn a lot about this from bonobos.

 

Written by stewart henderson

December 29, 2018 at 9:18 pm