The Magic of Reality Read Free Page B

now why what we see in real life is not the result of chance or luck or anything remotely ‘magical’ at all (except, of course, in the strictly poetic sense of something that fills us with awe and delight).
    The slow magic of evolution
    To turn one complex organism into another complex organism in a single step – as in a fairytale – would indeed be beyond the realms of realistic possibility. And yet complex organisms
do
exist. So how did they arise? How, in reality, did complicated things like frogs and lions, baboons and banyan trees, princes and pumpkins, you and me come into existence?
    For most of history that was a baffling question, which no one could answer properly. People therefore invented stories to try to explain it. But then the question was answered – and answered brilliantly – in the nineteenth century, by one of the greatest scientists who ever lived, Charles Darwin. I’ll use the rest of this chapter to explain his answer, briefly, and in different words from Darwin’s own.
    The answer is that complex organisms – like humans, crocodiles and Brussels sprouts – did not come about suddenly, in one fell swoop, but gradually, step by tiny step, so that what was there after each step was only a little bit different from what was already there before. Imagine you wanted to create a frog with long legs. You could give yourself a good start by beginning with something that was already a bit like what you wanted to achieve: a frog with short legs, say. You would look over your short-legged frogs and measure their legs. You’d pick a few males and a few females that had slightly longer legs than most, and you’d let them mate together, while preventing their shorter-legged friends from mating at all.
    The longer-legged males and females would make tadpoles together, and these would eventually grow legs and become frogs. Then you’d measure this new generation of frogs, and once again pick out those males and females that had longer-than-average legs, and put them together to mate.
    After doing this for about 10 generations, you might start to notice something interesting. The average leg length of your population of frogs would now be noticeably longer than the average leg length of the starting population. You might even find that
all
the frogs of the 10th generation had longer legs than any of the frogs of the first generation. Or 10 generations might not be enough to achieve this: you might need to go on for 20 generations or even more. But eventually you could proudly say, ‘I have made a new kind of frog with longer legs than the old type.’
    No wand was needed. No magic of any kind was required. What we have here is the process called
selective breeding
. It makes use of the fact that frogs vary among themselves and those variations tend to be inherited – that is, passed on from parent to child via the genes. Simply by choosing which frogs breed and which do not, we can make a new kind of frog.
    Simple, isn’t it?
    But just making legs longer is not very impressive. After all, we started with frogs – they were just short-legged frogs. Suppose you started, not with a shorter-legged form of frog, but with something that wasn’t a frog at all, say something more like a newt. Newts have very short legs compared with frogs’ legs (compared with frogs’
hind
legs, at least), and they use them not for jumping but for walking. Newts also have long tails, whereas frogs don’t have tails at all, and newts are altogether longer and narrower than most frogs. But you can see that, given enough thousands of generations, you could change a population of newts into a population of frogs, simply by patiently choosing, in each of those millions of generations, male and female newts that were slightly more frog-like and letting them mate together, while preventing their less frog-like friends from doing so. At no stage during the process would you see any dramatic change. Every generation would look