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how evolution was proved to be true

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The origin of species is a natural phenomenon

Jean-Baptiste Lamarck

The origin of species is an object of inquiry

Charles Darwin

The origin of species is an object of experimental investigation

Hugo de Vries

(quoted in The Gene: an intimate history, by Siddhartha Mukherjee)

Gregor Mendel

I’ve recently read Siddhartha Mukherjee’s monumental book The Gene: an intimate history, a work of literature as well as science, and I don’t know quite where to start with its explorations and insights, but since, as a teacher to international students some of whom come from Arabic countries, I’m occasionally faced with disbelief regarding the Darwin-Wallace theory of natural selection from random variation (usually in some such form as ‘you don’t really believe we come from monkeys do you?’), I think it might be interesting, and useful for me, to trace the connections, in time and ideas, between that theory and the discovery of genes that the theory essentially led to.

One of the problems for Darwin’s theory, as first set down, was how variations could be fixed in subsequent generations. And of course another problem was – how could a variation occur in the first place? How were traits inherited, whether they varied from the parent or not? As Mukherjee points out, heredity needed to be both regular and irregular for the theory to work.

There were few clues in Darwin’s day about inheritance and mutation. Apart from realising that it must have something to do with reproduction, Darwin himself could only half-heartedly suggest an unoriginal notion of blending inheritance, while also leaning at times towards Lamarckian inheritance of acquired characteristics – which he at other times scoffed at.

Mukherjee argues here that Darwin’s weakness was impracticality: he was no experimenter, though a keen observer. The trouble was that no amount of observation, in Darwin’s day, would uncover genes. Even Mendel was unable to do that, at least not in the modern DNA sense. But in any case Darwin lacked Mendel’s experimental genius. Still, he did his best to develop a hypothesis of inheritance, knowing it was crucial to his overall theory. He called it pangenesis. It involved the idea of ‘gemmules’ inhabiting every cell of an organism’s body and somehow shaping the varieties of organs, tissues, bones and the like, and then specimens of these varied gemmules were collected into the germ cells to produce ‘mixed’ offspring, with gemmules from each partner. Darwin describes it rather vaguely in his book The Variation of Animals and Plants under Domestication, published in 1868:

They [the gemmules] are collected from all parts of the system to constitute the sexual elements, and their development in the next generation forms the new being; but they are likewise capable of transmission in a dormant state to future generations and may then be developed.

Darwin himself admitted his hypothesis to be ‘rash and crude’, and it was effectively demolished by a very smart Scotsman, Fleeming Jenkin, who pointed out that a trait would be diluted away by successive unions with those who didn’t have it (Jenkin gave as an example the trait of whiteness, i.e. having ‘white gemmules’, but a better example would be that of blue eyes). With an intermingling of sexual unions, specific traits would be blended over time into a kind of uniform grey, like paint pigments (think of Blue Mink’s hit song ‘Melting Pot’).

Darwin was aware of and much troubled by Jenkin’s critique, but he (and the scientific world) wasn’t aware that a paper published in 1866 had provided the solution – though he came tantalisingly close to that awareness. The paper, ‘Experiments in Plant Hybridisation’, by Gregor Mendel, reported carefully controlled experiments in the breeding of pea plants. First Mendel isolated ‘true-bred’ plants, noting seven true-bred traits, each of which had two variants (smooth or wrinkled seeds; yellow or green seeds; white or violet coloured flowers; flowers at the tip or at the branches; green or yellow pods; smooth or crumpled pods; tall or short plants). These variants of a particular trait are now known as alleles. 

Next, he began a whole series of painstaking experiments in cross-breeding. He wanted to know what would happen if, say, a green-podded plant was crossed with a yellow-podded one, or if a short plant was crossed with a tall one. Would they blend into an intermediate colour or height, or would one dominate? He was well aware that this was a key question for ‘the history of the evolution of organic forms’, as he put it.

He experimented in this way for some eight years, with thousands of crosses and crosses of crosses, and the more the crosses multiplied, the more clearly he found patterns emerging. The first pattern was clear – there was no blending. With each crossing of true-bred variants, only one variant appeared in the offspring – only tall plants, only round peas and so on. Mendel named them as dominant traits, and the non-appearing ones as recessive. This was already a monumental result, blowing away the blending hypothesis, but as always, the discovery raised as many questions as answers. What had happened to the recessive traits, and why were some traits recessive and others dominant?

Further experimentation revealed that disappeared traits could reappear in toto in further cross-breedings. Mendel had to carefully analyse the relations between different recessive and dominant traits as they were cross-bred in order to construct a mathematical model of the different ‘indivisible, independent particles of information’ and their interactions.

Although Mendel was alert to the importance of his work, he was spectacularly unsuccessful in alerting the biological community to this fact, due partly to his obscurity as a researcher, and partly to the underwhelming style of his landmark paper. Meanwhile others were aware of the centrality of inheritance to Darwin’s evolutionary theory. The German embryologist August Weismann added another nail to the coffin of the ‘gemmule’ hypothesis in 1883, a year after Darwin’s death, by showing that mice with surgically removed tails – thus having their ‘tail gemmules’ removed – never produced tail-less offspring. Weismann presented his own hypothesis, that hereditary information was always and only passed down vertically through the germ-line, that’s to say, through sperm and egg cells. But how could this be so? What was the nature of the information passed down, information that could contain stability and change at the same time?

The Dutch botanist Hugo de Vries, inspired by a meeting with Darwin himself not long before the latter’s death, was possessed by these questions and, though Mendel was completely unknown to him, he too looked for the answer through plant hybridisation, though less systematically and without the good fortune of hitting on true-breeding pea plants as his subjects. However, he gradually became aware of the particulate nature of hereditary information, with these particles (he called them ‘pangenes’, in deference to Darwin’s ‘pangenesis’), passing down information intact through the germ-line. Sperm and egg contributed equally, with no blending. He reported his findings in a paper entitled Hereditary monstrosities in 1897, and continued his work, hoping to develop a more detailed picture of the hereditary process. So imagine his surprise when in 1900 a colleague sent de Vries a paper he’d unearthed, written by ‘a certain Mendel’ from the 1860s, which displayed a clearer understanding of the hereditary process than anyone had so far managed. His response was to rush his own most recent work into press without mentioning Mendel. However, two other botanists, both as it happened working with pea hybrids, also stumbled on Mendel’s work at the same time. Thus, in a three-month period in 1900, three leading botanists wrote papers highly indebted to Mendel after more than three decades of profound silence.

Hugo de Vries

The next step of course, was to move beyond Mendel. De Vries, who soon corrected his unfair treatment of his predecessor, sought to answer the question ‘How do variants arise in the first place?’ He soon found the answer, and another solid proof of Darwin’s natural selection. The ‘random variation’ from which nature selected, according to the theory, could be replaced by a term of de Vries’ coinage, ‘mutation’. The Dutchman had collected many thousands of seeds from a wild primrose patch during his country rambles, which he planted in his garden. He identified some some 800 new variants, many of them strikingly original. These random ‘spontaneous mutants’, he realised, could be combined with natural selection to create the engine of evolution, the variety of all living things. And key to this variety wasn’t the living organisms themselves but their units of inheritance, units which either benefitted or handicapped their offspring under particular conditions of nature.

The era of genetics had begun. The tough-minded English biologist William Bateson became transfixed on reading a later paper of de Vries, citing Mendel, and henceforth became ‘Mendel’s bulldog’. In 1905 he coined the word ‘genetics’ for the study of heredity and variation, and successfully promoted that study at his home base, Cambridge. And just as Darwin’s idea of random variation sparked a search for the source of that variation, the idea of genetics and those particles of information known as ‘genes’ led to a worldwide explosion of research and inquiry into the nature of genes and how they worked – chromosomes, haploid and diploid cells, DNA, RNA, gene expression, genomics, the whole damn thing. We now see natural selection operating everywhere we’re prepared to look, as well as the principles of ‘artificial’ or human selection, in almost all the food we eat, the pets we fondle, and the superbugs we try so desperately to contain or eradicate. But of course there’s so much more to learn….

William Bateson

Written by stewart henderson

June 14, 2017 at 5:42 pm

clever Charlie Darwin

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A photo taken by me! King Charles seated in state in the Musuem of Natural History, London. It was a thrill to be granted an audience

A photo taken by me! King Charles seated in state in the Musuem of Natural History, London. It was a thrill to be granted an audience

I recently decided to reread Darwin’s Origin of Species, which was really reading it for the first time as my first reading was pretty cursory, and I could barely follow the wealth of particular knowledge he used for cumulative effect to adduce his theory. This time I’ve been doing a closer reading, and becoming increasingly impressed, and I’ve only read the first chapter, ‘Variation under Domestication’.

Darwin’s argument here of course is that domesticated horses, dogs, birds and plants have been artificially selected over long periods of time, and often unconsciously, to suit human needs and tastes. This might seem screamingly obvious today, and to a degree it was recognised in Darwin’s time, but because of an inability to take the long view, and also because of the then-prevalent paradigm of the fixity of species, breeders and nurserymen tended to under-estimate their own cumulative powers, and to claim, for example, that dogs and pigeons had always come in many varieties. Even Darwin was uncertain, and was willing to concede – writing of course before the advent of Mendelian genetics, never mind the revolution wrought by the identification and analysis of DNA as the molecule of inheritance – that in some cases the breeders might be right:

In the case of most of our anciently domesticated animals and plants, I do not think it is possible to come to any definite conclusion, whether they have descended from one or several species.

He was even prepared to concede that it was ‘highly probable that our domestic dogs have descended from several wild species’, while at the same time arguing that the breeding of dogs, in Egypt, other parts of Africa and Australia (where, in his Beagle travels, he observed dingoes, which he may have seen as semi-domesticated by the Aborigines) extended back far further in time than most people suspected. We now know that Darwin’s concession here was ‘premature’. The latest research strongly suggests that our domesticated dogs trace their ancestry to a group of European wolves dating from 19,000 to 32,000 years ago, and probably now extinct. That’s a time-frame Darwin would’ve baulked at, and it’s both funny and kind of tragic that this is something I’ve ‘discovered’ after 30 seconds of selective internet searching. There’s no doubt, though that Darwin’s bold but always informed speculations were heading in the right direction.

Particularly informed –  and bold – were his speculations about pigeons. This is hardly surprising as he spent several years studying and breeding them himself. Interestingly, he started doing so because he’d become convinced that all the fancy pigeons then on show were most likely derived from one common species, the rock pigeon or rock dove (Columba livia), a view already held by some naturalists but few breeders.  He devotes several pages in Chapter 1 to arguing his case, for example pointing out that the ‘several distinct species’ argued for by breeders can be crossed with complete success, that’s to say with no signs of sterility or more than usually defective offspring.

So, as with dogs, I decided to look up what the latest research was on the ancestry of English carriers, short-faced tumblers, runts, fantails, common tumblers, barbs, pouters, trumpeters and laughers, to name some of the pigeons Darwin mentions in the chapter, and was excited to find that a piece of research published as recently as 2013 has confirmed Darwin’s hypothesis. Cheaper and faster genome sequencing technologies have enabled researchers to sequence the genomes of many wild and domesticated birds, and they’ve found that all of the latter are clearly closer to C livia than to any other wild species. It only took just over 150 years for Darwin to be proven correct.

Close reading like this really does reap some fun rewards, and I’ll finish with two more examples. Darwin wrote of how in the world of breeding, quite a drastic change can be brought about in one breeding step, as in the case of the fuller’s teasel with its hooks. He goes on:

So it has probably been with the turnspit dog; and this is known to have been the case with the ancon sheep.

Not knowing wtf he was talking about, I irritatedly decided to look up these unknown creatures. The turnspit dog is a now-extinct breed, bred specifically from around the 16th century to provide the dogpower to turn meat on a spit, the only conceivable way of cooking large joints of meat in your average fancy household for a couple of centuries. The dog, or dogs, because the system worked better if you had two of them engaged in shift work, turned a wheel by running inside it, rat-like, until the meat was cooked. They were known to be long-bodied and short-legged, but details of how they were bred aren’t known, as they were apparently beneath scholarly consideration. They certainly weren’t seen as cuddly pets – if you treat creatures as slaves it heightens your contempt for then (cf Aristotle) – and they were even taken to church as foot-warmers. They’d disappeared entirely by the end of the 19th century.

It's a dog's life?

It’s a dog’s life?

The ancon sheep was a short-legged type, apparently bred from a single individual in the USA in the late nineteenth century, its short legs having the singular advantage, to some, of curtailing its hopes of freedom by jumping the fence. The term ‘ancon’ has since been used by breeding researchers to describe strains of creatures arising from an individual with the same phenotype.


Written by stewart henderson

June 4, 2016 at 11:00 am

this one’s for the birds

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Canto: If anybody doesn’t appreciate the beauty and complexity and general magnificence of birds they should pee off and never darken this blog again.

Jacinta: Right. Now what brought that on, mate?

Canto: Oh just a general statement of position vis-à-vis other species. Charles Darwin, an old friend of mine, was pretty disdainful of human specialness in his correspondence, but he kept a low profile – on this and everything else – in public. I want to be a bit more overt about these things. And one of the things that really amazes me about birds, apart from their physical beauty, is how much goes on in those teeny noggins of theirs.

Jacinta: Yes, but what really brought this on? I haven’t heard you rhapsodising about birds before.

Canto: You haven’t been inside my vast noggin mate. Actually I’ve been taking photos – or trying to – of the bird life around here; magpies, magpie-larks, crows, rainbow lorikeets, honeyeaters, galahs, corellas, sulphur-crested cockies, as well as the pelicans, black swans, cormorants, moorhens, coots and mallard ducks by the river, not to mention the ubiquitous Australian white ibis and the masked lapwing.

Jacinta: Well I didn’t know you cared. Of course I agree with you on the beauty of these beasties. Better than any tattoo I’ve seen. So you’re becoming a twitcher?

Canto: I wouldn’t go that far, but I’ve been nurturing my fledgling interest with a book on the sensory world of birds, called, appropriately, Bird sense, by a British biologist and bird specialist, Tim Birkhead. It’s divided into sections on the senses of birds – a very diverse set of creatures, it needs to be said. So we have vision, hearing, smell, taste, touch, and that wonderful magnetic sense that so much has been made of recently.

Jacinta: So we can’t generalise about birds, but I know at least some of them have great eyesight, as in ‘eyes like an eagle’.

Canto: Well, as it happens, our own Aussie wedge-tailed eagle has the most acute sense of vision of any creature so far recorded.

Jacinta: Well actually it isn’t ours, it just happens to inhabit the same land-form as us.

Canto: How pedantic, but how true. But Birkhead points out that there are horses for courses. Different birds have vision adapted for particular lifestyles. The wedge-tail’s eyes are perfectly adapted to the clear blue skies and bright light of our hinterland, but think of owl eyes. Notice how they both face forward? They’re mostly nocturnal and so they need good night vision. They’ve done light-detection experiments with tawny owls, which show that on the whole they could detect lower light levels than humans. They also have much larger eyes, compared with other birds. In fact their eyes are much the same size as ours, but with larger pupils, letting in more light. They’ve worked out, I don’t know how, that the image on an owl’s retina is about twice as bright as on the average human’s.

Jacinta: So their light-sensitivity is excellent, but visual acuity – not half so good as the wedge-tailed eagle’s?

wedge-tailed eagle - world's acutest eyes

wedge-tailed eagle – world’s acutest eyes

Canto: Right – natural selection is about adaptation to particular survival strategies within particular environments, and visual acuity isn’t so useful in the dark, when there’s only so much light around, and that’s why barn owls, who have about 100 times the light-sensitivity of pigeons, also happen to have very good hearing – handy for hunting in the dark, as there’s only so much you can see on a moonless night, no matter how sensitive your eyes are. They also learn to become familiar with obstacles by keeping to the same territory throughout their lives.

face of a barn owl - 'one cannot help thinking of a sound-collecting device, quoth researcher Masakazu Konishi

face of a barn owl – ‘one cannot help thinking of a sound-collecting device’, quoth researcher Masakazu Konishi

Jacinta: So they don’t echo-locate, do they?

Canto: No, though researchers now know of a number of species, such as oilbirds, that do. Barn owls, though, have asymmetrical ear-holes, one being higher in the head than the other, which helps them to pinpoint sound. It was once thought that they had infra-red vision, because of their ability to catch mice in apparently total darkness, but subsequent experiments have shown that it’s all about their hearing, in combination with vision.

Jacinta: Well you were talking about those amazing little brains of birds in general, and I must say I’ve heard some tales about their smarts, including how crows use cars to crack nuts for them, which must be true because it was in a David Attenborough program.

Canto: Yes, and they know how to drop their nuts near pedestrian crossings and traffic lights, so they can retrieve their crushed nuts safely. The genus Corvus, including ravens, crows and rooks, has been a fun target for investigation, and there’s plenty of material about their impressive abilities online.

seeing is believing

seeing is believing

Jacinta: So what other tales do you have to tell, and can you shed any light on how all this cleverness comes in such small packages?

Canto: Well Birkhead has been studying guillemots for years. These are seabirds that congregate on cliff faces in the islands around Britain, and throughout northern Europe and Canada. They’re highly monogamous, and get very attached to each other, and thereby hangs another fascinating tale. They migrate south in the winter, and often get separated for lengthy periods, and it’s been noted that when they spot their partner returning, as a speck in the distance, they get highly excited and agitated, and the greeting ceremony when they get together is a joy to behold, apparently – though probably not as spectacular as that of gannets. Here’s the question, though – how the hell can they recognise their partner in the distance? Common guillemots breed in colonies, butt-to-butt, and certainly to us one guillemot looks pretty well identical to another. No creature could possibly have such acute vision, surely?

Jacinta: Is that a rhetorical question?

Canto: No no, but it has no answer, so far. It’s a mystery. It’s unlikely to be sight, or hearing, or smell, so what is it?

Jacinta: What about this magnetic sense? But that’s only about orientation for long flights, isn’t it?

Canto: Yes we might discuss that later, but though it’s obvious that birds are tuned into their own species much more than we are, the means by which they recognise individuals are unknown, though someone’s bound to devise an ingenious experiment that’ll further our knowledge.

Jacinta: Oh right, so something’s bound to turn up? Actually I wonder if the fact that people used to say that all Chinese look the same, which sounds absurd today, might one day be the case with birds – we’ll look back and think, how could we possibly have been so blind as to think all seagulls looked the same?

Canto: Hmmm, I think that would take a lot of evolving. Anyway, birds are not just monogamous (and anyway some species are way more monogamous than others, and they all like to have a bit on the side now and then) but they do, some of them, have distinctly sociable behaviours. Ever heard of allopreening?

Jacinta: No but I’ve heard the saying ‘birds of a feather flock together’ and that’s pretty sociable. Safety in numbers I suppose. But go on, enlighten me.

Canto: Well, allopreening just means mutual preening, and it usually occurs between mates – and I don’t mean in the Australian sense – but it’s also used for more general bonding within larger groups.

Jacinta: Like, checking each other out for fleas and such, like chimps?

Cant: Yeah, though this particular term is usually reserved for birds. Obviously it serves a hygienic purpose, but it also helps calm ruffled feathers when flocks of colonies live beak by jowl. And if you ever get close enough to see this, you’ll notice the preened bird goes all relaxed and has this eyes half-closed, blissed-out look on her face, but we can’t really say that coz it’s anthropomorphising, and who knows if they can experience real pleasure?

Jacinta: Yes, I very much doubt it – they can only experience fake pleasure, surely.

Canto: It’s only anecdotal evidence I suppose, but that ‘look’ of contentment when birds are snuggling together, the drooping air some adopt when they’ve lost a partner, as well as ‘bystander affiliation’, seen in members of the Corvus genus, all of these are highly suggestive of strong emotion.

Jacinta: Fuck it, let’s stop beating about the bush, of course they have emotions, it’s only human vested interest that says no, isn’t it? I mean it’s a lot easier to keep birds in tiny little cages for our convenience, and to burn their beaks off when they get stressed and aggressive with each other, than to admit they have feelings just a bit like our own, right? That might mean going to the awful effort of treating them with dignity.

Canto: Yyesss. Well on that note, we might make like the birds and flock off…

how the flock do they do that?

how the flock do they do that?

Written by stewart henderson

November 13, 2015 at 12:06 pm

why is evolution true? (if it is): part two, the problem of macroevolution

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So, in Darwin’s day, there was a clear problem. Fossilised bones turning up everywhere, sometimes of gigantic creatures unlike anything on earth, sometimes of creatures very like those then living but not quite the same – in any case all indicating change, change, change. And there were many other oddities, some of them observed by Darwin himself on his Beagle voyage. Marine fossils embedded in landscapes way above sea level. Darwin had a great interest in geology, courtesy of Charles Lyell, whose landmark work, Principles of Geology, he carried with him on his great voyage. He was very interested in Lyell’s view, derived from Hutton, that landscapes changed slowly, with mountains rising from the sea, over periods of time much greater than the biblical account. So imagine his mind, full of Lyell’s speculations, when on March 4 1835 he was exploring the cliffs above Talcuhano Harbour, near Concepcion in Chile, shortly after the devastating earthquake, and found maases of seashells embedded in the rock. The Andes had risen from the sea, surely! Yet he might well have been in two minds – slow change, yes, perhaps, but the earthquake had also changed the physical landscape in an instant, bringing rocks dripping and oozing with marine life up several feet above the sea surface…

Meanwhile, dinosaurs. Of course the bones of these critters have been unearthed for millenia, but it was only in the early nineteenth century that they were treated scientifically. It was Richard Owen, later to become Darwin’s bête noir, who coined the term in 1842 (it’s from the Greek, roughly meaning ‘terrible lizard’ though dinos weren’t lizards, and they weren’t all terrible, or terribly large). These huge beasts (dinos come in all sizes, but large bones are more easily preserved than small ones, giving a false picture, and of course bigness grabs the public imagination) had clearly disappeared, but when? Why? How long ago? It all made the question of the earth’s actual age and history rather more urgent.

Darwin, back in England after a richly stimulating voyage in which he’d collected and ruminated over a vast number of exotic species, was exercised by a number of problems. Why did whole species disappear? Surely this had some connection with changes of landscape and habitat? He’d been making observations with regard to predators and prey, how species depended on other species, how individuals competed for mates. It seems that, unlike Wallace who came upon the insight of natural selection more or less in one fell swoop years later, Darwin was piecing things together painfully slowly, with hesitation, scepticism and uncertainty, but also with a dogged accumulation of evidence, so that when, finally, impelled by the famous letter from Wallace in the late 1850s to express his views, he was able to do so fulsomely, in spite of a lack of writerly ability. And the rest, as they say, is history.

The theory of natural selection is the most spectacularly successful and productive theory in biology, and is in fact its foundation stone. It has been reinforced by all that has been discovered since, especially in genetics and microbiology, fields that didn’t exist in Darwin’s time. The basis of the theory is quite simple, though it has been much misrepresented. Creatures reproduce, and generally the offspring are pretty well identical to the parents, but sometimes mutations occur. The offspring is in some way different. Usually the difference is ‘negative’, disadvantaging the offspring. The offspring is thus unable to reproduce and its line dies out. Sometimes the difference is ‘neutral’ and the line continues to reproduce, until or unless natural (environmental) conditions change and that line becomes either positive or negative within the context of those conditions. In other words it thrives compared to others or it dies out. Sometimes the difference is immediately positive, and this line outcompetes the others. The variation is random, but the natural environment ‘selects’ the best fit – the birds with the best beak for pecking out food; the worms with the best chemistry for thriving in a particular soil; in more recent times, the bacteria that can best resist the antibiotics we throw at them.

So the theory of natural selection describes incremental, gradual change. Its effect upon species is more difficult to explain, and it’s with this that creationists like to play, raising lots of dust and fog with respect to the species concept.

So what exactly is a species? The first more or less universally accepted classification of living things into groups was that of Linnaeus in his Systema naturae of 1735. It was a thoroughgoing system, from kingdom at the top, ranging down through phylum, class, order, family, genus and species. It’s still used today, of course, with various additions intercalated with these layers, but in the 20th century a new taxonomic system called cladistics, based on a more scientific understanding of descent from common ancestry, and so incorporating the new science of genetics, has won increasing favour.

One of the main reasons for this new development is that the term ‘species’ has historically been  frustratingly vague. Originally it was based on morphological characteristics – in other words, visible similarities. Nowadays, though, with the emergence of population genetics and genomics, we can be more rigorous about species and speciation. Basically, a species becomes separated from another when it no longer breeds with that other. More often than not, this is due to geographic separation. Early on in the separation interbreeding is still possible, but over time, with continued lack of opportunity, the two groups become increasingly distinct and unlike (and one or both groups may go extinct). This branching has of course occurred oodles of times, creating an evolutionary bush, each twig of which can be traced back to the original stem.

So far, so clear, I hope. So where do the creationist terms micro-evolution and macro-evolution come in? Well, off the top of my head, I think that, since creationists really really dislike the theory of natural selection as presented by Darwin, they have to account for obvious changes somehow without abandoning divine creation, especially of humans, as soul-blessed, dominion-holding, image-of-god types. So, they distinguish micro-evolution, changes within species (e.g. different breeds of dogs) from macro-evolution, transformations from one species to another, which they claim doesn’t exist. Presumably they think that every species was specially created by their god, though why he should have created so many and rendered the vast majority of them extinct before humans even came on the scene is a mystery. This points up a major problem for those who believe in directed evolution as well as creationism.

Okay, to be clear, micro-evolution and macro-evolution aren’t terms invented by creationists, though they’ve taken to them like babies to their mothers’ milk. The terms were first used by evolutionary biologists early in the 20th century to characterise not different processes but different scales of evolution. Micro-evolution plus time (in which minute changes accumulate) equals macro-evolution. Creationists, then, are reduced to claiming that, because we don’t ‘see’ speciation, it doesn’t exist. Presumably they can say the same for the big bang and black holes, but we can detect such objects and events through increasingly precise instrumentation, and we can pretty well map the relations between species, and the branchings-off, by examining genomes. They tell us, for example, that we share an ancestor with our closest living relatives, the chimps and bonobos, dating back between 5 and 7 million years ago. We are equally related to these two species because they branched off from each other later, between one and a half and two million years ago. Richard Dawkins, in his monumental work The Ancestors’ Tale, attempted to trace these nodes of connections between the ancestors of humans and other species, back to the first life forms. There are gaps in our knowledge of course, but they’re being filled in on an almost daily basis.

As Dawkins points out in another of his books, River out of Eden, the DNA ‘revolution’ that got underway as a result of Watson and Crick’s unravelling of the molecular structure of the gene, is a digital revolution. The genetic code is quaternary, with four nucleotide elements – adenine, thymine, cytosine and guanine which can be combined in specific ways. Therefore the difference in the coding for different proteins, leading on the large scale to all the variation we see, can be worked out mathematically. This allows us to define more precisely our cousinship to other species – which are the more distant cousins, horses or pigs? Or, how closely connected are bees and butterflies? We can illustrate these relations using cladograms:



The technology we now have at our disposal allows us to map whole genomes increasingly cheaply and efficiently, and so we’re finding some surprising relationships. For example, recent DNA analysis has revealed that falcons, previously thought for fairly obvious reasons to be closely related to other birds of prey such as eagles, are in fact more closely related to parrots, songbirds and passerines such as the humble sparrow – a significant shift in taxonomic placement.

The obvious connections between species, and the fact that we can draw the evolutionary bush with increasing confidence, makes a mockery of creationist claims against natural selection, which not only explains speciation but also extinction. We may not know exactly why the neanderthals, or the trilobites, or the Australian megafauna died out, but natural selection points us in the right direction for answers – climate change, food scarcity and the introduction of new predators into the environment being the obvious candidates. The creationist, on the other hand needs to answer the question – why would their god keep creating these species, endlessly, only to have them snuffed out? No answers about the opacity of their god’s intentions are acceptable. And of course that’s far from being the only question they can’t answer.

Written by stewart henderson

June 13, 2015 at 5:14 pm

why is evolution true? (if it is): part one, the problem of fixity

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some Galapagos finches

some Galapagos finches

Much of my writing, especially about sciency stuff, is an attempt to own the knowledge. It’s perhaps never completely successful, especially for the non-specialist, the dilettante, who tries to own so much and to keep all those possessions together. You read about it, you cast it in your own words, you grasp it, you think you’ve grasped it completely, you move on to other things, and six months later you’re asked a curly question and in trying to answer it you find you’ve forgotten the half of it, and you wonder – did I ever really understand it after all?

So. We have the theory of evolution, or natural selection from random variation, and we have the theories of special and general relativity and quantum theory and so forth. And we have those in science who tell us that ‘theory’ is a technical term constantly misunderstood by the general public and deliberately misconstrued by those with particular agendas. And we have general talk and a lot of general ignorance about evolution.

Several years ago, when I was starting out as a teacher of ESOL (English to speakers of other languages) I observed a small community centre English class. The elderly teacher was asked by a well-dressed middle-aged African man, did she really think evolution – that we were descended from monkeys – was true? It was a polite, puzzled question. The teacher, understandably not wanting to dive down that rabbit hole, replied, ‘well, you know, it’s just a theory’, and the subject was changed. It unsettled me, to put mildly. It’s not how I would’ve dealt with the matter, and in fact I’ve twice since been placed in that position in recent times, and I’ve responded with ‘oh yes, it’s true, the evidence is in and it’s overwhelming,’ or words to that effect. Bam bam, take that and let’s back to grammar.

But of course, that response, too, is unsettling. After all, I could’ve given the exact same response to the question ‘Does God exist?’. It was just saying, an argument from my own authority.

Of course I had back-up from years of science and evolution-reading, but still I felt I was just imposing my authority as a teacher. I half-hoped for and half-dreaded being asked to elaborate.

The other night, at an atheist meet-up, the group was ‘invaded’ by three or four young street-preachers, self-confessed fundies who were apparently keen to debate evolution (they didn’t believe in it) and cosmology (the universe can’t create itself, ergo god). I didn’t engage with them myself, as I’m still recovering from a chest infection and want to avoid stress, but things got very heated over in their corner and I’ve since received an email asking for help to convince one of them of the evidence for evolution. It may be that the young man’s ignorance is wilful, but maybe not, and in any case it provides me with a useful opportunity to answer as best I can the title question.

Questions were raised about the fixity of species well before Charles Darwin was born. The most important figures in this early questioning of orthodoxy came from France. One of the founders of naturalism, Buffon, speculated that the earth might be much older than the standard biblical 6000 years, and that change, both geological and organic, might be endemic and constant. He mostly kept his views to himself, as the idea that the earth was maybe more than ten times older than the accepted figure was incendiary for the time. Lamarck, however, was the first to really go public with a theory of evolution. His essential view was that creatures adapted to their environment over time through the inheritance of acquired characteristics. Although he was generally incorrect as to his mechanism there is still some interest in his ideas today, but above all Lamarck strongly influenced future thinking on the subject as he was a first-rate scientist.

It should be noted though that all this speculation was brought on by the problems posed by evidence. The biblical fixity of species account was becoming increasingly difficult to reconcile with the discoveries of fossils of creatures not to be found anywhere, yet apparently related to current species. And then there were the fossils of ‘giants’, which had been discovered here and there for centuries, but which were not described scientifically until the nineteenth century. How could all these remains of  ‘disappeared’ creatures be turning up in a world where creation was fixed? The most popular explanation was ‘catastrophism’, a view held by Cuvier, a younger contemporary of Lamarck and one of his strongest critics. It was an attempt to reconcile fixity with a conveniently biblical diluvian view, but it continued to move thinking in a scientific, evidence-based direction.

Meanwhile, however, other fields of research, such as geology, were also becoming increasingly scientific, especially in Britain, with the work of Hutton and Lyell. Through inference from present conditions, they developed a gradualist, uniformitarian theory of physical change, with a more open-ended view of the earth’s age. This was the scientific background to Darwin’s naturalism. His own grandfather, Erasmus, dabbled in evolutionary ideas, and proposed that the earth had existed for ‘millions of ages’.

Now I know there’s a view out there among fundamentalists called ‘young earth creationism’, but I don’t know much about it. It would seem to be an absolutely crackpot notion, a denial of modern geology, astronomy and cosmology as well as biology and palaeontology, and I presume people who think this way consider the whole of modern science a massive conspiracy theory. How could they not? Yet the young man mentioned above has suggested we go and see a lecture by John Hartnett, an Adelaide University Associate Professor of Physics who’s also a young earth creationist. How could this be? Well I know something of cognitive dissonance and confirmation bias, but still I can barely imagine what he would say to justify his worldview, and I’m not really interested in trying to rebut his specific arguments, if he has them. These people tend to have martyr complexes about their positions, and I suspect they’d be happy to spend hours trying to bamboozle you. The main thing is to be clear about your own understanding of the evidence.

However, I also have an interest in the psychology of belief. Take the case of Hartnett, which I can only speculate about, but this is an obviously intelligent person who has apparently written scientific papers on dark matter and other aspects of cosmology and astrophysics. He knows, surely, how vast the universe is, that the Andromeda Galaxy, our nearest neighbour, is a barely-conceivable 2.5 million light years away, and there are billions of them beyond that, and yet he manages to square this with a six-day creation 6,000 years ago because it was written down by someone and collected much later with a whole mess of other writings by other people, compiled into a book and pronounced ‘holy’. Surely such thinking is more of a mystery than the gods themselves?

I can only speculate again, but Hartnett’s middle name is Gideon, a name inevitably associated with bible-bashing. Can it be that a person gets locked in, from earliest childhood, to a religious schema that they would never think to escape from, no matter how intelligent they are? Can cultural-familial influences have such a vice-like grip? Apparently so, but it’s unusual for someone to be regularly crossing the boundary between a rigid and dogmatic religious belief system and a highly speculative, often free-wheeling but rational and profoundly naturalist enterprise in the way that Hartnett must do. Ain’t people fascinating?

I’ve just read an article about rapid speciation among cichlid fishes in the African lakes. The authors note that this speciation, involving some 500 new species in Lake Victoria, has taken place over less than 15,000 years, unlike the famous speciation among ‘Darwin’s’ finches in the Galapagos (14 species, several million years). It’s called adaptive radiation, where ‘one lineage spawns numerous species that evolve specialisations to an array of ecological niches’, to quote Axel Meyer, writing in the April 2015 edition of Scientific American.

Yet this rapid speciation is still too much for young earth creationists, who believe the earth is less than 10,000 years old. What they make of stromatolites is anyone’s guess. Note that the term ‘earth’ is central, and presumably the universe or multiverse is of little concern to them, existing perhaps only as a fireworks show for our delectation.

As an Australian, this is all good for a laugh – though some Australians, such as John Hartnett, are full-on believers of a six-day creation a few thousand years ago – but apparently in the USA a substantial proportion of their very large population actually believes this (though to be honest, I can’t bring myself to believe the survey figures).

So, I wonder how I would deal with these young-turk young earth creationists who come to our atheist meet-ups spoiling for an argument. My hope is that I would have the wherewithal to ask these questions.

Is it your hope to convert the whole world to your view?

If you were successful, wouldn’t science classes be a lot shorter?

What would you do with those who insisted on being heretical? Preaching that the universe has existed for 13 billion years? Would you have them liquidated, or just permanently incarcerated? How about public recantations?

How come your god allowed us to be led astray by the evidence into getting it so wrong?

What would science be like if young earth creationists controlled all the levers of power? What would scientists do?

Of course I’m yet to hear what young earth creationists, many of whom are apparently highly intelligent, have to say about star formation, black holes and the big bang. They may well have the talent to bamboozle me with ingenious arguments. In the end, though, the best argument is to just keep doing the science, following the evidence. As long as we’re still allowed to.

Meanwhile, I haven’t yet answered the question – why is evolution (or more specifically, natural selection of random variation) true? But before I answer that, I believe that creationists do accept evolution of a particular kind, and distinguish between ‘micro-evolution’ and ‘micro-evolution’. I’ll pay some attention to that – but perhaps not too much – in my next post.

Written by stewart henderson

June 8, 2015 at 6:56 am

reveries of a solitary wa*ker: wa*k 2

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bulldog Tommy about to land a bookish blow

bulldog Tommy about to land a bookish blow

The Darwin book continues to be a rollicking good read, I’m into the post Origin period, where shit hits the fans and Darwin’s fans, led by that young Turkish bulldog Tommy Huxley, shovel shit on the opposition, captained by soapy Sam Wilberforce and the brains of high Anglicanism, Dicky Owen – the most gifted naturalist of his age, to be fair. What’s fascinating is that the Origin precipitated the last great politico-religious struggle in England, a very drawn-out affair which crossed the Atlantic and continues in the US to this day, but in England it has been a slow-acting poison to conservative Anglicanism. Liberal Anglicanism, essentially a bridge to atheism, has swallowed natural selection with a sort of diffident, dumb grace, flexible as to their god’s ever-changing plan. As a semi-student of history though, I can well understand Darwin’s own diffidence about publicizing his theory. It was bad enough for the time, had it been a century earlier (impossible of course given the eighteenth century state of knowledge) he would absolutely have been martyred for it. As it was, during the couple of decades between formulating his theory and going public, the public, especially the disaffected Chartist ‘rabble’, had become increasingly keen for a weapon to strike down the High Clergy and the swanningly civilised aristos, and apes for ancestors, monkeys for uncles, even gorillas for girlfriends, fitted the bill perfectly. Darwin, of course, presented his case as dispassionately as humanly possible, with nary a mention of human descent, and afterwards kept his head down in Downe, obsessing over pigeons and orchids and sexual selection (actually chipping away very effectively at the god-did-it argument), while Tommy Huxley, Joe Hooker and co fought the good Darwinian battle in the big smoke with consummate derring-do (don’t believe a word of this by the way, as if you would). Darwin was anything but a fighter – he had vomiting fits at the very thought of confrontation – but in his oddly reclusive way he was always the leader, because unlike many of his supporters, even the closest ones, he knew he was right. His aim, his obsession, with all his apparently arcane researches, was to keep adding to the mountain of evidence.

There are many intriguing things about Darwin. He was vain but genuinely humble, highly-strung and emotional but profoundly analytical, a hypochondriac and yet a real invalid for stretches of his life, and of course a revolutionary who hated revolutionaries. As a young, footloose, disgustingly well-heeled intellectual, he could think of nothing better than to make a pleasant living as a naturalist-clergyman, like many a gentleman among his family’s connections. By his career’s end, the naturalist-clergyman was becoming a relic, probably more due to his own productions than to any other cause.

The founding father of eugenics, atheism, Nazism, bestiality and please don’t get me started


And this leads to a consideration of his most profound impact, outside the confines of science, what makes him the most controversial and contested, and in some circles reviled, figure of the past two hundred years, and that is his, and his theory’s, complete denial of human specialness. A specialness which is at the heart of the Abrahamic religions, without which not.

This recognition of human relatedness to other species, the bringing of humans back to the pack, wasn’t an anti-Christian urge by any means, it was more a result of his obsessive interest in solving the problems of adaptation and basic survival of creatures such as barnacles, earthworms and pigeons. This obsession gave him great respect for the sometimes barely fathomable complexity and ingenuity of even the most ‘basic’ life-forms. He saw human complexity as a continuation of that adaptive process, but biologists and many other scientists were, at that time, unable to shake off notions of human exceptionality. Owen, Wallace, Luis Agassiz, Asa Gray, Charles Lyell, St George Mivart and others of Darwin’s time, all had qualms about, or simply rejected outright, the implications for humanity of Darwinian natural selection, and these represented the scientific mainstream, essentially. Darwin himself was able to weather the storm through the support of strong allies such as Hooker and Huxley, his own ability to avoid and deflect controversy, his inaccessibility at Downe, his long-suffering but profoundly loyal wife, and his habit of retreating into the messy fine detail of his studies. He also, through voluminous correspondence – he would’ve loved the world of email and Facebook – built up a huge network of scientific boffins, breeders and farmers, with whom he was unfailingly polite and charming while exploiting their specialist knowledge. So he was able to adapt very well to the challenges thrown at him.



I’m writing here as if delivering a lecture, and I do wish I could reach more people. I don’t have too many contacts with a penchant for science, or for history, but then I don’t have many contacts. But enough complaining (mea culpa after all), I note that the vaccination controversy drags on, with too many people standing on their ‘right’ to not vaccinate their children, which shows up the problems with the rights concept, which I’ve always considered artificial but a useful fiction which has helped to build a more humane global society, and speaking of globalism the battle to save the lives of Australians under the death penalty is almost over, but we should continue the battle to the end because it’s a bad law and national sovereignty be damned, and that should be the same for any national under any national or state law. Which makes me wonder, I’m not a lawyer, but what would happen if an Australian citizen was charged with a capital offence and sentenced to death in the notorious US state of Texas? Maybe they only kill US citizens, that’d keep them out of international trouble, but what we need to keep working on is an international code of ethics and an international law and I do think we’re creeping towards it slowly slowly.

capital punishment - green doesn't do it, red does, and yellow's moving away

capital punishment – green doesn’t do it, red does, and yellow’s moving away

Written by stewart henderson

April 9, 2015 at 6:53 am

reveries of a solitary wa*ker: wa*k 1

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(Being a thousand words or so of mental drivel)

I’d prefer not to be coy about the title but I’ve a job to protect.

the delightful enthusiasm of children

the delightful enthusiasm of children

Began watching documentary series chronicles of the third reich, yet another rake-over of that terrible but ghoulishly fascinating period, and it kicked off with noted historian Ian Kershaw saying that the regime was unique in that it aimed to overthrow the entire Judeo-Christian system of ethics that sustained western Europe for centuries. Bullshit I say. No such thing. What nazism was overthrowing, or delaying or subverting, was the progress of western Europe, for example the Renaissance and the Enlightenment, movements towards democracy, individual liberty, internationalism, none of which owed anything to the Judeo-Christian belief system. This lazy thinking and remarking continually goes unchallenged. At the height of Judeo-Christian control we had monarchical dictatorships, divine right, religious authoritarianism, extreme corruption, torture, rigid hierarchies, feudal slavery, etc, a world of inhumanity and brutality. Not saying that Christianity caused this, life wouldn’t have been any better in China or Japan, doubtless. Depended on chance and ‘birthright’ as to how well you fared.


Reading the big bio of Darwin by Desmond and Moore, thinking how so much that was radical or extreme becomes mainstream within a few generations, such as materialism, atheism, democratic principles, equality for women, humans as apes. Chartism’s aims – extension of suffrage, taxation reform, the repeal of laws too unjust to be enacted nowadays, all horrific to the upper classes, who armed themselves with crowbars to protect their homes and privileges. And among them, quite a few favouring transmutation (though not of the Darwinian kind – more a sort of Lamarckian progressive development towards the human pinnacle) and atheistic science. Makes you think of today’s accelerating trends, e.g gay marriage. All these ideas were opposed because they would bring down civilisation as we know it. Rock n roll was another one.
Also thinking how science threatened and continues to threaten religion. Moslem student asked me last week, do you think humans come from apes? Could see what his hopes were, was happy to crush them and move on. No doubt he’ll return to Saudi, ask the question again and be reassured as to his human specialness. But maybe not. But in Darwin’s day, so many associates, Sedgwick, Henslow, Lyell, Owen, Whewell, even Herschel, even bloody Wallace, couldn’t countenance our ‘demotion’ to a primate, on grounds some of them didn’t even recognise as religious. How can it possibly be argued that religion and science are compatible? Only if we have a very different religion, and perhaps a very different science – panpsychism, spooky action at a distance, positively conscious positrons.

A love-hate thing with Darwin, all his stuffy aristocratic connectedness, his family’s money, but then his boldness of ideas, but then his timidity born of an unwillingness to offend, a need to be admired, feted, but two kinds of glory, the one for a grand idea that might just outlast the opprobrium of his elite class in mid-nineteenth century England, the other for being a model member of that class, civilized, restrained, highly intelligent, pushing gently outwards the boundaries of knowledge. The tension between immediate, hail-fellow-well-met acceptance and something more, his dangerous idea, something barely digestible but profoundly transformative.


Keep reading about the hard problem of consciousness, without greatly focusing. Don’t really believe in it. We’re surely just at the beginning of getting to grips with this stuff – but how much time do we have? Dennett talks of the mind as cultural construct, Cartesian theatre as he calls it, and you don’t need to have ever heard of Descartes to wonder at how memories, rehearsals, fantasies can be played out inside the head, inaccessible to everyone but yourself, but without the boundaries of the skull, or of a theatre, no straightforward boundaries of space or time, yet composed of reality-bits, physical and emotional. One of my first serious wonderings, I seem to remember (not trustworthy) was about this boundary-less but secret place-thing called the mind. Not sure about a cultural construct, seemed very real and self-evident to me, and a wonderful safe haven where you can think and do things for which you’ll never get arrested, never have to apologise, a theatre of blood, sex and brilliance…

But I don’t think I thought then, and I don’t think now, that this was anything other than a product of the brain because to me the brain was like every other organ, the heart, the liver, the kidneys, the lungs, they were all mysterious, I didn’t know how any of them worked, and though I knew that I could learn a lot more about them, and would over the course of my life, I suspected that nobody knew everything about how any of them functioned, and the brain was just more complex and so would contain more mysteries than any of the others perhaps put together, but it had to come from the brain because, well everybody said thoughts were produced by the brain and these were just thoughts after all and where else could they come from – there was no alternative. And it seems we’re slowly nutting it out, but humans are understandably impatient to find answers, solutions. We like to give prizes for them.


Also reading Natalie Angier’s Woman, a revised version of a book brought out in the nineties. It’s a popular biology book from a good feminist perspective, and I’m learning much about breast milk and infant formula, about the breast itself, about menstruation, about the controversies around hysterectomies and so on, but her style often irritates, drawing attention to too much clever-clever writing rather than the subject at hand. It’s a tricky area, you want your writing lively and engaging, not like reading an encyclopedia, but especially with science writing you want it all to be comprehensible and transparent – like an encyclopedia. Angier sometimes uses metaphors and puns and (for me) arcane pop references which have me scratching my head and losing the plot, but to be fair it’s worth persevering for the content. But it shouldn’t be about persevering.