Archive for the ‘complexity’ Category
on epigenetics and the free will debate, and such…
The free will thing has come to the fore of my head again recently because of an offhand ‘no free will’ remark I made, which of course caused some friendly argy-bargy. When the topic comes up I like to throw ‘the lot’ at it, our early neurological wiring, unwiring and rewiring, our hormonal activity, our genetics, our epigenetics, our position in the womb, our early interactions with parents, siblings and others, our culture, our gender, our first language, the time and place of our birth and so on.
Of all these variables, epigenetics is one that’s likely to catch people off guard. If they ask, I’ll say it’s all about gene expression, hoping that will silence them, and even impress them. But if they inquire further, I’d only be able to say something like ‘environmental factors affect how genes are expressed’ – and that would be the limit of my knowledge, even though, some years ago, I read Nessa Carey’s The epigenetics revolution, published in 2011.
So now I’m reading it again, and it seems for the first time. I’m finding it really hard to understand, and I’m sure it isn’t Carey’s fault. I suspect it’s the kind of topic in which you need to be active in the field to fully understand it, and even then….
But, I’ll have a go. Rett syndrome is a rare but devastating neurological disease which occurs almost exclusively in girls. Apparently, if a male child contracts it, it’s more or less immediately fatal. As AI (never lies) puts it:
Infants typically develop normally for 6 to 18 months before experiencing a severe regression in motor skills, speech, and hand use. While there is no cure, symptoms can be managed with targeted therapies and specific medications.
The development of this syndrome happened to coincide with infants receiving the MMR vaccine, which, as we know, caused much controversy some time ago, but the mechanism was worked out in 1999. It mostly has to do with mutations in a gene called MECP2, which severely affects the production of a functional MECP2 protein. Dysfunction/mutation in other genes have caused the syndrome, or something like it, in a minority of cases. The cells are able to methylate their DNA correctly, which is what much of what epigenetics is all about, but they’re unable to read that section of the epigenetic code properly. So Rett syndrome isn’t a mental/psychological disorder at all, it’s purely genetic, and because the dysfunction is on the X chromosome, and because females have two X chromosomes while males have XY, the male karyotype is more vulnerable to the condition.
I choose this extreme condition (suffered by one in 8500 females) as one among many examples of how our genetics can fail us, and there are many others, much more subtle and hard to pin down, both in terms of our genes themselves and how they are expressed. We – I mean the scientists and researchers among us, and those going along for the ride – have learned especially in recent decades just how complex and beyond our control our brains and bodies are, not just in terms of physical make-up, but genetic and cultural inheritance. A regular awareness of this – a mindfulness, if you like – helps me to cope with the people who damage our world – the war-mongers, the bullies, the intolerant and over-confident – as well as to sympathise with the overwhelmed (like myself).
So, again to epigenetics – I’ll keep trying to comprehend at least some of it, as it’s intrinsically interesting when it’s not completely baffling. Meanwhile, I’ve had a book recommended to me, by two humanists and no-free-will proponents, called Being: why it’s harder to be human than a hamster or a herring, by a daughter and father duo, Rachel and Ross Menzies. Sounds like an antidote to all that epiphenomena…
References
Nessa Carey, The Epigenetics Revolution: How modern biology is rewriting our understanding of genetics, disease and inheritance, 2011.
the evolution of complexity
Gould’s view of the movement to complexity
I’m not sure if this is a controversial topic – perhaps it depends on whether you think complexity is in some sense superior to simplicity regarding organic life, and I suspect that we humans are a bit biased on the issue.
Bacteria and archaea are still thriving in our biosphere, in vast numbers. These two classes or domains of prokaryote differ in various ways. The eukaryotes, the third domain into which organisms have been divided, are believed to have evolved from an ancestor of modern archaea.
A question. With such forms of life thriving from billions of years ago, why become more complex? In what way would it have been more advantageous? But in thinking of advantage, aren’t we thinking outside of the prokaryotic box? Shouldn’t scientists (I’ve seen this written) confine themselves to ‘how’ questions rather than ‘why’ questions? But since I’m neither a scientist nor a philosopher, I don’t know what to think.
In any case, ‘how’ questions seem quite a bit easier to answer. One way to think about it, I suppose, is to think of ‘accidents’, or simply differences, that confer an advantage. What might be called imprecise (or just varied) replications mostly wouldn’t survive, but some would turn out to be beneficial to survival, and so, over eons – complexity.
Problem solved.
Stephen Jay Gould provides an explanation for complexity in his book Life’s Grandeur, which I find overly verbose, but I think I can simplify it, in my simple way. These early prokaryotes would’ve replicated themselves almost perfectly, but not quite. Sometimes, very rarely, they would’ve missed something, or messed something up, during replication, called binary fission in prokaryotes. This would mostly have made the next generation non-viable, because generally prokaryotes are so tiny and simple that if they were any simpler they’d come up against a ‘wall’ of non-viability. The only way a different but viable next gen could be created would be if something was added rather than subtracted.
But how could this happen? Well, the ‘addition’ might be something genetic, but let’s not go there for now – Darwin didn’t need genetics to develop his theory of natural selection, nor did he need a concept of progress, though, unsurprisingly, he fell into that trap now and again. I’ve not looked deeply into binary fission but maybe the fission might occasionally lead to something not quite the same as its predecessor, in the way that archaea are not quite the same as bacteria, or that the first eukaryotes weren’t quite the same as those ancestral archaea. That’s the funny thing about the term ‘evolved from’ – it’s so easy to say, but a lot harder to pin down precisely. Anyway, maybe some kind of genetic ‘doubling up’ made some difference, a hardiness, a more diverse diet – if prokaryotes can be said to have diets. In any case, it was all about ‘more’ – a very all-encapsulating four-letter word. For example, think of stromatolites, those colonies of cyanobacteria. Was it colonisation from the start, or did some genetic change create this kind of super-organic effect?
All of this is as hard to pin down precisely as life from non-life, but we know it happened. And we also know that once life got itself well started, it thrived pretty much everywhere, not just over our planet, but quite deeply under the surface, in the most unlikely places. And considering the vast numbers, all of them replicating, the possibility of something more complicated surviving and battening on to others in an advantageous way becomes plausible, surely.
So, prokaryotes to eukaryotes. Were there intermediate stages? Let’s look at the differences. Eukaryotes are all the life we see. Prokaryotes are invisible to us without microscopes, etc. We’ve divided them into archaea and bacteria, based on a number of differences, notably the structure of their cell walls, but these structures also differ between species of bacteria. Gould has explored the issue of ‘progress’ and complexity from a bacterial perspective in the lengthy penultimate chapter of Life’s grandeur, entitled ‘The Power of the Modal Bacter, or Why the Tail can’t Wag the Dog’. I looked up Modal Bacter online and came up empty, which is why Gould irritates me so, as a writer for ‘the general public’. I’m guessing it means the bacterial mode of life. I’m going to use Gould’s chapter for the rest of this post, which looks like being a long one. So, at the beginning of the chapter, he writes this:
… simple forms still predominate in most environments, as they always have. Faced with this undeniable fact, supporters of progress (that is, nearly all of us throughout the history of evolutionary thought) have shifted criteria and ended up grasping at straws. (The altered criterion may not have struck the graspers as such a thin reed, for one must first internalise the argument of this book – trends as changes in variation rather than things moving somewhere – to recognise the weakness).
I’m not quite sure what this means, but ‘progress’ sticks out. We can make progress in learning a language/trade/sport, but has life made progress? I would tend to agree that this term isn’t useful from an evolutionary perspective. The criterial shift is surely toward complexity, and this is surely happening in the human line of development. Unfortunately we can’t measure neural complexity in our most recent ancestors – the closest living connections we have are chimps/bonobos, and here’s something from the Cambridge University Press website:
while chimpanzee brains are markedly smaller than those of humans, their brain anatomy is so similar that a discourse comparing the two might be little different from this declaration: The chimpanzee brain is a human brain with one-third of the neurons (Herculano-Houzel & Kaas, 2011).
This odd observation – very similar anatomy with one third of neurons – is a head-scratcher. I would have thought that neural organisation, perhaps especially in the prefrontal cortex, would be key here. After all, isn’t this the point of such comparisons? We’re looking at neurology to help us understand the differences we see in the culture and behaviour of Pan troglodytes and Homo sapiens, are we not? And it’s surely fair enough to say our human behaviour is more complex, what with our language, our science, our culture, our cities and whatnot? To point this out is not to be hubristic. In pointing this out we need to be aware, and many of us are, of the downsides – our altering of the atmosphere, our responsibility for species loss, and so on. I should also point out, since I’ve mentioned hubris, that free will is a myth, as I’ve argued in more than one previous post. I didn’t choose to be human, it just happened to me. Not my achievement. Nothing to be proud or ashamed of. Just something to make sense of, as best I can.
So, bearing this in mind, human complexity is worth studying, and it’s not about patting ourselves on the back. This particular complexity of humans – and it may be that, in the vastness of the universe, different living complexities have evolved – is clearly a product of evolution. We wouldn’t be here without the ‘Modal Bacter’, as Gould calls it, or without the chain of connection that goes back to the earliest life forms.
So, it seems to me, that Gould, in trying to question, or demolish, the pedestal he believes we have placed ourselves on, and to give himself credit for so doing, is missing the point by raising up the ‘Modal Bacter’, as if it should somehow be given obeisance for being the great survivor and the great progenitor, while we are the mere accidental offshoots. Take this quote (along with my insertion):
Wind back the tape of life to the origin of modern multicellular animals in the Cambrian explosion [or indeed to the ‘Modal Bacter’ millions of years before], let the tape play again from this identical starting point, and the replay will populate the earth (and generate a right tail of life) with a radically different set of creatures. The chance that this alternative set will contain anything remotely like a human being must be effectively nil, while the probability of any kind of creature endowed with self-consciousness must also be vanishingly small.
S J Gould, Life’s grandeur, p 214
There’s an obvious flaw in the logic here. If you take the tape back to the Cambrian explosion or any other point in time and replay it, you’ll get the same result, because it’s the same tape! What he presumably means, is that if some condition was changed back in the Cambrian, or earlier, then a very different result would ensue for later generations. Or, that we humans are just ‘accidents’ resulting from particular initial, or previous, conditions. And so with all life, including his much-vaunted bacteria. Not to mention all planets, stars, etc. This should hardly be seen as a revelation. Which makes me wonder just what Gould is on about.
So let’s explore further. Here’s another of his ‘critiques’:
Under the traditional model of evolutionary history as a ‘cone of increasing diversity’, life moves ever upward to greater progress, and outward to a larger number of species – from simple Cambrian beginnings for multicellular animals to our modern levels of progress and range of diversity. Under this iconography, pathways actually followed run along predictable courses that would be at least roughly repeated in any replay.
Again I find this sort of writing overly tendentious. Either life has become more diverse in expression or it has not, and this has nothing to do with progress. And researchers are exploring this question, hopefully without recourse to ‘iconography’. It may be, as Gould argues, that vertebrates were in a ‘tenuous position’ before the Cambrian explosion and that, with some tweaking of prehistory, they wouldn’t have survived and we wouldn’t be here. So presumably this means we should be more humble and less overlordly. But is this something to be humble about, or proud of? Maybe it’s worth being aware of, just as I wouldn’t exist if my parents hadn’t met. But the fact is, they did, and vertebrates didn’t go extinct. So, if we stick with the facts, life would be a little more tractable. And no need to worry about progress or perhaps even complexity. We find complexity everywhere, from bacteria to the biosphere, and on to black holes and big bangs. It’s such a fun world to explore! And that’s the thing that easily makes me remain ‘umble. The world’s complexity isn’t my doing, obviously, and I hardly comprehend even the tiniest part of it….
References
Archaea vs. Bacteria
Stephen Jay Gould, Life’s grandeur, 1996