The Science of Discworld III - Darwin's Watch

18. STEAM ENGINE TIME

THERE WAS DARWIN, SITTING ON a bank, watching the bees, the wasps, the flowers ... In the last paragraph of The Origin we find a beautiful and important passage that hints at afternoons of that kind: It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.

Go ahead Paley, make my day.

All that wizardly effort to get him to write The Origin, not The Ology. It mattered to Darwin, of course, and it matters to those who chart the course of history. But, just as we can ask whether Lincoln's assassination really had much effect on subsequent events, so we can ask the same about Darwin's life's work. Would it really have mattered if the wizards had failed?

Metaphorical wizards, you appreciate. Yes, those happy coincidences that got Charles on board the Beagle and kept him there do look a tad suspicious, but wizards?

Let's ask the question in a more respectable way. How radical was Darwin's theory of natural selection, really? Did he have insights that no one before him had considered? Or did he just happen to be the person who caught the public eye, with an idea that had been floating around for some time? How much credit should he be given?

The same can be - and has been - asked of many `revolutionary' scientific concepts. Robert Hooke got the idea of inverse square-law gravity before Newton did. Minkowski, Poincare, and others worked out much of special relativity before Einstein did. Fractals were around, in some form, for at least a century before Benoit Mandelbrot energetically promoted them and they developed into a major branch of applied mathematics. The earliest sniff of chaos theory can be found in Poincare's prize-winning memoir on the stability of the solar system in 1890, probably 75 years before the subject was perceived as `taking off.

How do scientific revolutions get started, and what decides who gets the credit? Is it talent? A flair for publicity? A lottery?

Part of the answer to these questions can be found in Robert Thurston's 1878 study of another important Victorian innovation, which Ponder Stibbons unerringly homed in on in Chapter 3. The book is A History of the Growth of the Steam Engine. The second paragraph says: History illustrates the very important truth: inventions are never, as great discoveries are seldom, the work of any one mind. Every great invention is really either an aggregation of minor inventions, or the final step in a progression. It is not a creation, but a growth as truly so as is that of the trees in the forest. The same invention is frequently brought out in several countries, and by several individuals, simultaneously.

Thurston's topic reminds us of a common metaphor for this kind of apparently simultaneous invention: steam engine time. When it's steam engine time, suddenly everyone is making steam engines. When it's evolution time, everyone is inventing a theory of evolution. When it's VCR time, everyone is making video cassette recorders. When it's Dotcom time, everyone is setting up Internet trading systems. And when it's Dotcom-going-bust time, all the Dotcoms are going bust.

There are times when human affairs really do seem to run on preconstructed tracks. Some development becomes inevitable, and suddenly it's everywhere. Yet, just before that propitious moment, it wasn't inevitable at all, otherwise it would have happened already. `Steam engine time' is a convenient metaphor for this curious process. The invention of the steam engine wasn't the first example, and it certainly wasn't the last, but it is one of the best known, and it's quite well documented.

Thurston distinguishes invention from discovery. He says that inventions are never the creation of a single individual, whereas great discoveries seldom are. However, the distinction isn't always clearcut. Did ancient humans discover fire as a phenomenon of nature, or did they invent fire as a technology to keep predators away, light the cave, and cook food? The natural phenomenon surely came first, in the form of brush- or forest fires triggered by lightning, or possibly a droplet of water accidentally acting as a lens to concentrate the Sun's rays on to a piece of dry grass[46].

However, that kind of `discovery' doesn't go anywhere until someone finds a use for it. It was the idea of controlling fire that made the difference, and that seems more of an invention than a discovery. Except ... you find out how to control fire by discovering that fires don't spread (so easily) across bare soil, that they can be spread very easily indeed by picking up a burning stick and dropping it into dry brushwood, or taking it home to the cave ...

The inventive step, if there is such a thing, consists of putting together several independent discoveries so that what emerges has genuine novelty.

Dry grass and drops of water are not commonly associated, but perhaps a damp elephant had just emerged from a river crossing on to dry savannah ... Oh, invent your own explanation.

So inventions are often preceded by a series of discoveries. Similarly, discoveries are often preceded by inventions. The discovery of sunspots rested on the invention of the telescope, the discovery of amoebas and parameciums in pond water rested on the invention of the microscope. In short, invention and discovery are intimately entwined, and it's probably pointless to try to separate them. Moreover, the significant instances of both are much easier to spot in retrospect than they were at the time they first happened. Hindsight is a wondrous thing, but it does have the virtue of providing an explicit context for working out what did, or did not, matter. Hindsight lets us organise the remarkably messy process of invention/discovery, and tell convincing stories about it.

The problem is, most of those stories aren't true.

As children, many of us learned how the steam engine was invented. The young James Watt, aged about six, was watching a kettle boil, and he noticed that the pressure of the steam could lift the lid. In a classic `eureka' moment, it dawned on him that a really big kettle could lift really heavy bits of metal, and the steam engine was born.

The original teller of this story was the French mathematician Francois Arago, author of one of the first biographies of Watt. For all we know, the story may be true, though it is more likely a `lie-tochildren', or educational aid,* like Newton's apple. Even if the young Watt was indeed suddenly inspired by a boiling kettle, he was by no means the first person to make the connection between steam and motive power. He wasn't even the first person to build a working steam engine. His claim to fame rests on something more complex, yet more significant. In Watt's hands, the steam engine became an effective and reliable tool. He didn't `perfect' it - many smaller improvements were made after Watt - but he brought it into pretty much its final form.

Watt wrote in 1774: `The fire engine (= steam engine) that I have invented is now going, and answers much better than any other that has yet been made.' In conjunction with his business partner Matthew Boulton, Watt made himself the household name of the steam engine. And it has done his reputation no harm that, in the words of Thurston: `Of the personal history of the earlier inventors and improvers of the steam-engine, very little is ascertained; but that of Watt has become well known.'

Was Darwin just another Watt? Did he get credit for evolution because he brought it into a polished, effective form? Is he famous because we happen to know so much about his personal history? Darwin was an obsessive record-keeper, he hardly threw away a single scrap of paper. Biographers were able to document his life in exceptional detail. It certainly did his reputation no harm that such a wealth of historical material was available.

In order to make comparisons, let's review the history of the steam engine, avoiding lies-to-children as much as we can. Then we'll look at Darwin's intellectual predecessors, and see whether a common pattern emerges. How does steam engine time work? What factors lead to a cultural explosion, as an apparently radical idea `takes off and the world changes for ever? Does the idea change the world, or does a changing world generate the idea?

Watt completed his first significant steam engine in 1768, and patented it in 1769. It was preceded by various prototypes. But the first recorded reference to steam as a source of motive power occurs in the civilisation of ancient Egypt, during the Late Kingdom when that country was under Roman rule. Around 150 BC (the date is very approximate) Hero of Alexandria wrote a manuscript Spiritalia seu Pneumatica. Only partial copies have survived to the present day, but from them we learn that the manuscript referred to dozens of steam-driven machines. We even know that several of them predated Hero, because he tells us so; some were the previous work of the inventor Cestesibus, celebrated for the great number and variety of his ingenious pneumatic machines. So we can see the beginnings of steam engine time long ago, but initial progress was so quiet and slow that steam engine time itself was still far in the future.

One of Hero's devices was a hollow airtight altar, with the figure of a god or goddess on top, and a tube running through the figure. Unknown to the punters, the altar contains water. When a worshipper lights a fire on top of the altar, the water heats up and produces steam. The pressure of the steam drives some of the remaining liquid water up the pipe, and the god offers a libation. (As miracles go this one is quite effective, and distinctly more convincing than a statue of a cow that oozes milk or one of a saint that weeps.) Similar devices were commonplace from the 1960s to make tea at the bedside and pour it out automatically. They still exist today, but are harder to find.

Another of Hero's machines used the same principle to open a temple door when someone lit a fire on an altar. The device is quite complicated, and we describe it to show that these ancient machines went far beyond being mere toys. The altar and door are above ground, the machinery is concealed beneath. The altar is hollow, filled with air. A pipe runs vertically down from the altar into a metal sphere full of water, and a second inverted U-shaped pipe acts like a siphon, with one end inside the sphere and the other inside a bucket. The bucket hangs over a pulley, and ropes from the bucket wind round two vertical cylinders, in line with the hinges of the door and attached to the door's edge. They then run over a second pulley and terminate in a heavy weight which acts as a counterbalance. When a priest lights the fire, the air inside the altar expands, and the pressure drives water out of the sphere, through the siphon, and into the bucket. As the bucket descends under the weight of water, the ropes cause the cylinders to turn, opening the doors.

Then there's a fountain that operates when the sun's rays fall on it, and a steam boiler that makes a mechanical blackbird sing or blows a horn. Yet another device, often referred to as the world's first steam engine, boils water in a cauldron and uses the steam to turn a metal globe about a horizontal axis. The steam emerges from a series of bent pipes around the sphere's `equator', at right angles to the axis.

In design, these machines weren't toys, but as far as their applications went, they might as well have been. Only the door-opener comes close to doing anything we would consider practical, although the priests probably found the ability to produce miracles on demand to be quite profitable, and that's practical enough for most businessmen today.

Looking back from the twenty-first century, it seems astonishing that it took steam engine time so long to gain proper momentum, with all these examples of steam power on public display all over the ancient world. Especially since there was plenty of demand for mechanical power, for the same reasons that finally gave birth to steam engine technology in the eighteenth century - pumping water, lifting heavy weights, mining, and transport. So we learn that it takes more than the mere ability to make steam engines, even in conjunction with a clear need for something of that kind, to kick-start steam engine time.

And so the steam engine bumbled along, never disappearing entirely, but never making any kind of breakthrough. In 1120 the church at Rheims had what looks suspiciously like a steam-powered organ. In 1571 Matthesius described a steam engine in a sermon. In 1519 the French academic Jacob Besson wrote about the production of steam and its mechanical uses. In 1543 the Spaniard Balso de Garay is reputed to have suggested the use of steam to power a ship. Leonardo da Vinci described a steam-gun that could throw a heavy metal ball. In 1606 Florence Rivault, gentleman of the bedchamber to Henry IV, discovered that a metal bombshell would explode if it was filled with water and heated. In 1615, Salomon de Caius, an engineer under Louis XIII, wrote about a machine that used steam to raise water. In 1629 ... but you get the idea. It went on like that, with person after person reinventing the steam engine, until 1663.

In that year Edward Somerset, Marquis of Worcester, not only invented a steam-powered machine for raising water: he got it built, and installed, two years later, at Vauxhall - now part of London, but then just outside it. This was probably the first genuine application of steam power to a serious practical problem. No drawing of the machine exists, but its general form has been inferred from grooves, still surviving, in the walls of Raglan Castle, where it was installed. Worcester planned to form a company to exploit his machine, but failed to raise the cash. His widow in her turn made the same attempt, with the same lack of success. So that's another necessary ingredient for steam engine time: money.

In some ways, Worcester was the true creator of the steam engine, but he gets little credit, because he was just a tiny bit ahead of the wave. He does mark a moment at which the whole game changed, however: from this point on, people didn't just invent steam engines - they used them. By 1683, Sir Samuel Morland was building steampowered pumps for Louis XIV, and his book of that year reveals a deep familiarity with the properties of steam and the associated mechanisms. The idea of the steam engine had now arrived, along with a few of the things themselves, earning their living by performing useful tasks. But it still wasn't steam engine time.

Now, however, the momentum began to grow rapidly, and what gave it a really big push was mining. Mines, for coal or minerals, had been around for millennia, but by the start of the eighteenth century they were becoming so big, and so deep, that they ran into what quickly became the miner's greatest enemy: water.

The deeper you try to dig mines, the more likely they are to become flooded, because they are more likely to run into underlying reservoirs of water, or cracks that lead to such reservoirs, or just cracks down which water from above can flow. Traditional methods of removing water were no longer successful, and something radically different was needed. The steam engine filled the gap neatly. Two people, above all, made it possible to build suitable machinery: Dennis Papin and Thomas Savery.

Papin trained in mathematics under the Jesuits at Blois, and in medicine in Paris, where he settled in 1672. He joined the laboratory of Robert Boyle, who would nowadays be called an experimental physicist. Boyle was working on pneumatics, the behaviour of gases -'Boyle's law', relating the pressure and volume of a gas at constant temperature, continues to be taught to this day. Papin invented the double air pump and the air gun, and then he invented the Digester. This is best described as a pressure-cooker, which is a saucepan with thick walls and a thick lid, held on securely so that water inside boils to form high-pressure steam. Food contained in the pan cooks very quickly.

The cookery aspect doesn't affect our story, but one bit of technology does. To avoid explosions, Papin added a safety valve, a feature replicated in the sixties domestic version, and an important invention because early involvement with steam engines was dangerous at the best of times. The idea probably originated earlier, but Papin gets the credit for using it to control steam pressure. In 1687 he moved to the University of Marburg, where he invented the first mechanical steam engine and the first piston engine. Throughout his career, he carried out innumerable experiments with steam-related apparatus, and introduced many significant pieces of gadgetry.

Steam engine time was hotting up. Savery, who also trained in mathematics, brought it to the boil. In 1698 he patented the first steam-powered pump that was actually used to clear mines of unwanted water - in this case, the deep mines of Cornwall. He sent a working model to the Royal Society, and later showed a model `fire engine', as the machines were then confusingly called, to William III. The King granted him a patent: A grant to Thomas Savery of the sole exercise of a new invention by him invented, for raising of water, and occasioning motion to all sorts of mill works, by the important force of fire, which will be of great use in draining mines, serving towns with water, and for the working of all sorts of mills, when they have not the benefit of water nor constant winds; to hold for 14 years; with usual clauses.

Steam engine time was close at hand. What clinched it was that Savery was a born businessman. He didn't wait for the world to beat a path to his door: he advertised. He gave lectures at the Royal Society, some of which were published in its journals. He circulated a prospectus among mine-owners and managers. And the selling point, naturally, was profit. If you can open up deeper levels of your mine, you can extract more minerals and make more money out of the same mine and the same bit of land.

Two more major steps were needed before what Thurston calls the `modern' steam engine - that of 125 years ago - became firmly established. The first was to move from specialised, single-purpose machines, to multi-purpose ones. The second was to improve the engine's efficiency.

The move to multi-purpose steam engines was made by Thomas Newcomen, a blacksmith by trade, who introduced a radical new kind of engine, the `atmospheric steam engine'. Previous engines had effectively combined a steam-driven piston and a pump in the same apparatus. Newcomen separated the components, and threw in a separate boiler and a condenser to boot. The piston moves up and down like a `nodding donkey', driving a rod, which can be attached to ... anything you like. Another engineer who must be mentioned here was John Smeaton, who scaled Newcomen's design up to much larger size.

Now, finally, we come to James Watt. Whatever credit he deserves, it is clear that he stood on the shoulders of a number of giants. Even if he had been capable of inventing the steam engine on his own, the plain fact is that he didn't. His grandfather was a mathematician - there seem to be a lot of mathematicians in the history of the steam engine - and Watt inherited his abilities. He carried out lots of experiments, and he made quantitative measurements, a relatively new idea. He worked out how heat travelled through the materials of the engine, and how much coal it took to boil a given amount of water. And he realised that the key to an efficient steam engine was to control unnecessary heat loss. The worst loss occurred in the cylinder that powered the piston, which kept changing temperature. Watt realised that the cylinder should always be kept at the same temperature as the steam that entered it - but how could that be done? The answer, when he finally chanced upon it, was simple and elegant: I had gone to take a walk on a fine Sabbath afternoon. I had entered the Green by the gate at the foot of Charlotte Street, and had passed the old washing-house. I was thinking upon the engine at the time, and had gone as far as the herd's house, when the idea came into my mind that, as steam was an elastic body, it would rush into a vacuum, and, if a communication were made between the cylinder and an exhausted vessel, it would rush into it, and might be condensed there without cooling the cylinder ... I had not walked farther than the Golfhouse, when the whole thing was arranged in my mind.

Such an easy thing to come up with - don't cool the steam in the cylinder, cool it somewhere else. Yet it improved the machine's efficiency so much that within a few years the only steam engines that anyone even thought of installing were those of Watt and his financial partner Boulton. Boulton-and-Watt engines cornered the market. No really significant improvements were subsequently made to their design. Or, to be more accurate, later `improvements' supplanted the steam engine with engines of a very different design, driven by coal and oil. The steam engine had evolved to the pinnacle of its existence, and what displaced it was, in effect, a new species of engine altogether.

In retrospect, steam engine time arrived around the period of Savery, when the ability to make practical machines coincided with a genuine need for them in an industry that could afford to pay for them and would make more profits as a result. Add to that a sound business mind, to notice the situation and exploit it, and a sense for publicity to raise money from investors and get the idea off the ground, and the steam engine went like a ... train.

Ironically, before most people realised that steam engine time had arrived, it had gone again, and in the end there was only one winner. The rest of the competition fell by the wayside. And that is why Watt gets so much credit, and why, ultimately, he deserves it. But he also deserves credit for his systematic quantitative experiments, his focus on the theory behind the steam engine, and his development of the concept - not as its inventor.

Certainly not for watching a kettle as a kid.

The history of the introduction of the Boulton-and-Watt steam engine is essentially an evolutionary one: the fittest design survived, the less fit were superseded and vanished from the historical record. Which brings us to Darwin, and natural selection. The Victorian era was `steam engine time' for evolution; Darwin was just one of many people who recognised the mutability of species. Does he deserve the credit he gets? Was he, like Watt, the person who brought the theory to its culmination? Or did he play a more innovative role?

In the introduction to Origin, Darwin mentions several of his predecessors. So he certainly wasn't trying to take credit for the ideas of others. Unless you subscribe to the rather Machiavellian school of thought that giving credit to others is just a sneaky way of damning them with faint praise. -One predecessor that he does not mention is perhaps the most interesting of all - his own grandfather, Erasmus Darwin. Perhaps Charles felt that Erasmus was a bit too nutty to mention, especially being a relative.

Erasmus knew James Watt, and may have helped him to promote his steam engine. They were both members of the Lunar Society, an organisation of Birmingham technocrats. Another was Josiah Wedgwood, Darwin's uncle Jos's grandfather and founder of the famous ceramics company. The 'Lunaticks' met once a month at the time of the full moon - not for pagan or mystic reasons, or because they were all werewolves, but because that way they could see their way easily as they rode home after a few drinks and a good meal.

Erasmus, a physician, could also turn a nifty hand to machinery, and he invented a new steering mechanism for carriages, a horizontal windmill to grind Josiah's pigments, and a machine that could speak the Lord's Prayer and the Ten Commandments. When the 1791 riots against `philosophers' (scientists) and for `Church and King' put paid to the Lunar Society, Erasmus was just putting the finishing touches to a book. Its title was Zoonomia, and it was about evolution.

Not, however, by Charles's mechanism of natural selection. Erasmus didn't really describe a mechanism. He just said that organisms could change. All plant and animal life, Erasmus thought, derived from living `filaments'. They had to be able to change, otherwise they'd still be filaments. Aware of Lyell's Deep Time, Erasmus argued that: In the great length of time, since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind, would it be too bold to imagine, that all warm-blooded animals have arisen from one living filament, which the first great cause endowed with animality, with the power of acquiring new parts, attended by new propensities, directed by irritations, sensations, volitions, and associations; and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down those improvements by generation to its posterity, world without end! If this sounds Lamarckian, that's because it was. Jean-Baptiste Lamarck believed that creatures could inherit characteristics acquired by their ancestors - that if, say, a blacksmith acquired huge muscular arms by virtue of working for years at his forge, then his children would inherit similar arms, without having to do all that hard work. Insofar as Erasmus envisaged a mechanism for heredity, it was much like Lamarck's. That did not prevent him having some important insights, not all of them original. In particular, he saw humans as superior descendants of animals, not as a separate form of creation. His grandson felt the same, which is why he called his later book on human evolution The Descent of Man. All very proper and scientific. But Ridcully is right. `Ascent' would have been better public relations.

Charles certainly read Zoonomia, during the holidays after his first year at Edinburgh University. He even wrote the word on the opening page of his `B Notebook', the origin of Origin. So his grandfather's views must have influenced him, but probably only by affirming the possibility of species change[47]. The big difference was that from the very beginning, Charles was looking for a mechanism. He didn't want to point out that species could change - he wanted to know bow they changed. And it is this that distinguishes him from nearly all of the competition.

The most serious competitor we have mentioned already: Wallace. Darwin acknowledges their joint discovery in the second paragraph of the introduction to Origin. But Darwin wrote an influential and controversial book, whereas Wallace wrote one short paper in a technical journal. Darwin took the theory much further, assembled much more evidence, and paid more attention to possible objections.

He prefaced Origin with `An Historical Sketch' of views of the origin of species, and in particular their mutability. A footnote mentions a remarkable statement in Aristotle, who asked why the various parts of the body fit together, so that, for example, the upper and lower teeth meet tidily, instead of grinding against each other. The ancient Greek philosopher anticipated natural selection: Wheresoever, therefore, all things together (that is all the parts of one whole) happened like as if they were made for the sake of something, these were preserved, having been appropriately constituted by an internal spontaneity; and whatsoever things were not thus constituted, perished, and still perish.

In other words: if by chance, or some unspecified process the components carried out some useful function, they would appear in later generations, but if they didn't, the creature that possessed them would not survive.

Aristotle would have made short shrift of Paley.

Next, Darwin tackles Lamarck, whose views date from 1801. Lamarck contended that species could descend from other species, mostly because close study shows endless tiny graduations and varieties within a species, so the boundaries between distinct species is much fuzzier than we usually think. But Darwin notes two flaws. One is the belief that acquired characteristics can be inherited - Darwin cites the giraffe's long neck as an example. The other is that Lamarck believed in `progress' - a one-way ascent to higher and higher forms of organisation.

A long series of minor figures follows. Among them is one noteworthy but obscure fellow, Patrick Matthew. In 1831, he published a book about naval timber, in which the principle of natural selection was stated in an appendix. Naturalists failed to read the book, until Matthew drew attention to his anticipation of Darwin's central idea in the Gardener's Chronicle in 1860.

Now Darwin introduces a better-known forerunner, the Vestiges of the Natural History of Creation. This book was published anonymously in 1844 by Robert Chambers; it is clear that he was also its author. The medical schools of Edinburgh were awash with the realisation that entirely different animals have remarkably similar anatomies, suggesting a common origin and therefore the mutability of species. For example, the same basic arrangement of bones occurs in the human hand, the paw of a dog, the wing of a bird, and the fin of a whale. If each were a separate creation, God must have been running out of ideas.

Chambers was a socialite - he played golf - and he decided to make the scientific vision of life on Earth available to the common man. A born journalist, Chambers outlined not just the history of life, but that of the entire cosmos. And he filled the book with sly digs at `those dogs of the clergy'. The book was an overnight sensation, and each successive edition slowly removed various blunders that had made the first edition easy to attack on scientific grounds. The vilified clergy thanked their God that the author had not begun with one of the later editions.

Darwin, who respected the Church, had to refer to Vestiges, but he also had to distance himself from it. In any case, he found it woefully incomplete. In his `Historical Sketch', Darwin quoted from the tenth `and much improved' edition, objecting that the anonymous author of Vestiges cannot account for the way organisms are adapted to their environments or lifestyles. He takes up the same point in his introduction, suggesting that the anonymous author would presumably say that: After a certain number of unknown generations, some bird had given birth to a woodpecker, and some plant to the misseltoe {sic}, and that these had been produced perfect as we now see them; but this assumption seems to me to be no explanation, for it leaves the case of the coadaptations of organic beings to each other and to their physical conditions of life, untouched and unexplained.

More heavyweights follow, interspersed with lesser figures. The first heavyweight is Richard Owen, who was convinced that species could change, adding that to a zoologist the word `creation' means `a process he knows not what'. The next is Wallace. Darwin reviews his interactions with both, at some length. He also mentions Herbert Spencer, who considered the breeding of domesticated varieties of animals as evidence that species could change in the wild, without human intervention. Spencer later became a major populariser of Darwin's theories. He introduced the memorable phrase `survival of the fittest', which unfortunately has caused more harm than good to the Darwinian cause, by promoting a rather simple-minded version of the theory.

An unexpected name is that of the Reverend Baden Powell, whose 1855 `Essays on the Unity of Worlds' states that the introduction of new species is a natural process, not a miracle. Credit for mutability of species is also given to Karl Ernst von Baer, Huxley, and Hooker.

Darwin was determined not to miss out anyone with a legitimate claim, and in all he lists more than twenty people who in various ways anticipated parts of this theory. He is absolutely explicit that he is not claiming credit for the idea that species can change, which was common currency in scientific circles - and, as Baden Powell shows, beyond. What Darwin is laying claim to is not the idea of evolution, but that of natural selection as an evolutionary mechanism.

So ... we come full circle. Does an innovative idea change the world, or does a changing world generate the idea?

Yes.

It's complicity. Both of these things happen - not once, but over and over again, each progressively altering the other. Innovations redirect the course of human civilisation. New social directions encourage further innovation. The world of human ideas, and the world of things, recursively modify each other.

That is what happens to a planet when a species evolves that is not merely intelligent, but what we like to call extelligent. One that can store its cultural capital outside individual minds. Which lets that capital grow virtually without limit, and be accessible to almost anybody in any succeeding generation.

Extelligent species take new ideas and run with them. Before the ink was dry on Origin, biologists and laymen were already trying to test its ideas, shoot them down, push them further. If Darwin had written Ology, and if nobody else had written something like Origin, then Victorian extelligence would have been enfeebled, and perhaps the modern world would have taken longer to arrive.

But it was evolution time. Somebody would have written such a book, and soon. And in that alternat(iv)e world of if, he or she would have got the credit instead.

So it's only fair to give Darwin the credit in this world. Steam engine time notwithstanding.