The Science of Discworld Revised Edition

did the Victorians. Until the nineteenth century, though, nobody seems to have realized that a very similar process might explain the remarkable diversity of life on Earth, from bacteria to bactrians, from oranges to orangutans.
    They didn’t appreciate that possibility for two reasons. When you bred dogs, what you got was a different kind of dog – not a banana or a fish. And breeding animals was the purest kind of magic: if a human being
wanted
a long thin dog, and if they started from short fat ones, and if they knew how the trick worked (if, so to speak, they cast the right ‘spells’) then they would
get
a long thin dog. Bananas, long and thin though they might be, were
not
a good starting point. Organisms couldn’t change species, and they only changed form within their
own
species because people wanted them to.
    Around 1850, two people independently began to wonder whether nature might play a similar game, but on a much longer timescale and in a much grander manner – and without any sense of purpose or goal (which had been the flaw in previous musings along similar lines). They considered a self-propelled magic: ‘natural’ selection as opposed to selection by people. One of them was Alfred Wallace; the other – far better known today – was Charles Darwin. Darwin spent years travelling the world. From 1831 to 1836 he was hired as ship’s naturalist aboard HMS
Beagle
, and his job was to observe plants and animals and note down what he saw. In a letter of 1877 he says that while on the
Beagle
he believed in ‘the permanence of species’, but on his return home in 1836 he began to think about the deeper meaning of what he had seen, and realized that ‘many facts indicated the common descent of species’. By this he meant that species that are different now probably came from ancestors that once belonged to the
same
species. Species must be able to change. That wasn’t an entirely new idea, but he also came up with an effective
mechanism
for such changes, and that
was
new.
    Meanwhile Wallace was studying the flora and fauna of Brazil and the East Indies, and comparing what he saw in the two regions, and was coming to similar conclusions – and much the same explanation. By 1858 Darwin was still mulling over his ideas, contemplating a grand publication of everything he wanted to say about the subject, while Wallace was getting ready to publish a short article containing the main idea. Being a true English gentleman, Wallace warned Darwin of his intentions so that Darwin could publish something first, and Darwin rapidly penned a short paper for the Linnaean Society, followed a year later by a book,
The Origin of Species
– a big book, but still not on the majestic scale that Darwin had originally intended. Wallace’s paper appeared in the same journal shortly afterwards, but both papers were officially ‘presented’ to the Society at the same meeting.
    What was the initial reaction to these two Earth-shattering articles? In his annual report for that year, the President of the Society, Thomas Bell, wrote that ‘The year has not, indeed, been marked by any of those striking discoveries which at once revolutionize, so to speak, the department of science in which they occur.’ However, this perception quickly changed as the sheer enormity of Darwin’s and Wallace’s theory began to sink in, and they took a lot of stick from Mustrum Ridcully’s spiritual brethren for daring to come up with a plausible alternative to Biblical creation. What was this epoch-making alternative? An idea so simple that everybody else had missed it. Thomas Huxley is said to have remarked, on reading
Origin:
‘How extremely stupid not to have thought of that.’
    This is the idea. You don’t need a human being to push animals into new forms; they can do it to themselves – more precisely:
to each other
. This was the mechanism of natural selection. Herbert Spencer, who did the important journalistic job of interpreting Darwin’s theory to the masses, coined the phrase, ‘survival of the fittest’ to describe it. The phrase had the advantage of convincing everybody that they understood what Darwin was saying, and it had the disadvantage of convincing everybody that they understood what Darwin was saying. It was a classic lie-to-children, and it deceives many critics of evolution to this day, causing them to aim at a long-disowned target, besides giving a spurious ‘scientific’ background to some extremely