The Magic of Reality Read Online Free

pretty much like the previous generation, but nevertheless, once enough generations had gone by, you’d start to notice that the average tail length was slightly shorter and the average pair of hind legs was slightly longer. After a very large number of generations, the longer-legged, shorter-tailed individuals might find it easier to start using their long legs for hopping instead of crawling. And so on.
    Of course, in the scenario I have just described, we are imagining ourselves as breeders, picking out those males and females that we want to mate together in order to achieve an end result that we have chosen. Farmers have been applying this technique for thousands of years, to produce cattle and crops that have higher yields or are more resistant to disease, and so on. Darwin was the first person to understand that it works
even when there is no breeder to do the choosing
. Darwin saw that the whole thing would happen
naturally
, as a matter of course, for the simple reason that some individuals survive long enough to breed and others don’t; and those that survive do so because they are better equipped than others. So the survivors’ children inherit the genes that helped their parents to survive. Whether it’s newts or frogs, hedgehogs or dandelions, there will always be some individuals that are better at surviving than others. If long legs happen to be helpful (for frogs or grasshoppers jumping out of danger, say, or for cheetahs hunting gazelles or gazelles fleeing from cheetahs), the individuals with longer legs will be less likely to die. They will be more likely to live long enough to reproduce. Also, more of the individuals available for mating with will have long legs. So in every generation there will be a greater chance of the genes for longer legs being passed into the next generation. Over time we will find that more and more of the individuals within that population have the genes for longer legs. So the effect will be exactly the same as if an intelligent designer, such as a human breeder, had chosen long-legged individuals for breeding – except that
no such designer is required
: it all happens naturally, all by itself, as the automatic consequence of which individuals survive long enough to reproduce, and which don’t. For this reason, the process is called
natural selection
.
    Given enough generations, ancestors that look like newts can change into descendants that look like frogs. Given even more generations, ancestors that look like fish can change into descendants that look like monkeys. Given yet more generations, ancestors that look like bacteria can change into descendants that look like humans. And this is exactly what happened. This is the kind of thing that happened in the history of every animal and plant that has ever lived. The number of generations required is larger than you or I can possibly imagine, but the world is thousands of millions of years old, and we know from fossils that life got started more than three and a half billion years ago, so there has been plenty of time for evolution to happen.
    This is Darwin’s great idea, and it is called Evolution by Natural Selection. It is one of the most important ideas ever to occur to a human mind. It explains everything we know about life on Earth. Because it is so important, I’ll come back to it in later chapters. For now, it is enough to understand that evolution is very slow and gradual. In fact, it is the gradualness of evolution that allows it to make complicated things like frogs and princes. The magical changing of a frog into a prince would be not gradual but sudden, and this is what rules such things out of the world of reality. Evolution is a real explanation, which really works, and has real evidence to demonstrate the truth of it; anything that suggests that complicated life forms appeared suddenly, in one go (rather than evolving gradually step by step), is just a lazy story – no better than the fictional magic of a